146-686: Heptaeniidae The Heptageniidae (synonym: Ecdyonuridae) are a family of mayflies with over 500 described species mainly distributed in the Holarctic , Oriental, and Afrotropical regions, and also present in the Central American Tropics and extreme northern South America. The group is sometimes referred to as flat-headed mayflies or stream mayflies . These are generally rather small mayflies with three long tails. The wings are usually clear with prominent venation although species with variegated wings are known. As in most mayflies,
292-436: A butterfly . The hind wings are much smaller than the forewings and may be vestigial or absent. The second segment of the thorax , which bears the forewings, is enlarged to hold the main flight muscles. Adults have short, flexible antennae, large compound eyes, three ocelli and non-functional mouthparts. In most species, the males' eyes are large and the front legs unusually long, for use in locating and grasping females during
438-445: A grasshopper , to jump into water and drown. Mayflies are involved in both primary production and bioturbation . A study in laboratory simulated streams revealed that the mayfly genus Centroptilum increased the export of periphyton , thus indirectly affecting primary production positively, which is an essential process for ecosystems. The mayfly can also reallocate and alter the nutrient availability in aquatic habitats through
584-518: A clean, unpolluted and highly oxygenated aquatic environment. They are unique among insect orders in having a fully winged terrestrial preadult stage, the subimago, which moults into a sexually mature adult, the imago . Mayflies "hatch" (emerge as adults) from spring to autumn, not necessarily in May, in enormous numbers. Some hatches attract tourists. Fly fishermen make use of mayfly hatches by choosing artificial fishing flies that resemble them. One of
730-511: A common ancestor, the archediction represents the "template" that has been modified (and streamlined) by natural selection for 200 million years. According to current dogma, the archedictyon contained six to eight longitudinal veins. These veins (and their branches) are named according to a system devised by John Comstock and George Needham—the Comstock-Needham system: The costa (C) is the leading marginal vein on most insects, although
876-450: A common tracheal stem in nymphal insects, and the veins are regarded as branches of a single anal vein. Distally, the vannal veins are either simple or branched. The jugal vein (J) of the jugal lobe of the wing is often occupied by a network of irregular veins, or it may be entirely membranous; sometimes it contains one or two distinct, small veins, the first jugal vein, or vena arcuata, and the second jugal vein, or vena cardinalis (2J). All
1022-488: A flat plate, the stipes, hinged to the cardo . Both cardo and stipes are loosely joined to the head by a membrane, so they are capable of movement. Distally on the stipes are two lobes, an inner lacinea, and an outer galea, one or both of which may be absent. More laterally on the stipes is a jointed, leglike palp made up of many segments; in Orthoptera, there are five. Anterior and posterior rotator muscles are inserted on
1168-425: A further moult. Adult mayflies, or imagos , are relatively primitive in structure, exhibiting traits that were probably present in the first flying insects. These include long tails and wings that do not fold flat over the abdomen. Mayflies are delicate-looking insects with one or two pairs of membranous, triangular wings, which are extensively covered with veins . At rest, the wings are held upright, like those of
1314-429: A great quantity of organic matter as nymphs and transfer a lot of phosphates and nitrates to terrestrial environments when they emerge from the water, thus helping to remove pollutants from aqueous systems. Along with caddisfly larvae and gastropod molluscs , the grazing of mayfly nymphs has a significant impact on the primary producers , the plants and algae, on the bed of streams and rivers. The nymphs are eaten by
1460-422: A hardened proteinaceous matrix, which forms much of the exoskeleton . In its pure form, it is leathery, but when encrusted in calcium carbonate , it becomes much harder. The difference between the unmodified and modified forms is evident when comparing the body wall of a caterpillar (unmodified) to a beetle (modified). From the embryonic stages, a layer of columnar or cuboidal epithelial cells gives rise to
1606-526: A large hatch was observed at midday in June. The soft-bodied subimagos are very attractive to predators. Synchronous emergence is probably an adaptive strategy that reduces the individual's risk of being eaten . The lifespan of an adult mayfly is very short, varying with the species. The primary function of the adult is reproduction; adults do not feed and have only vestigial mouthparts , while their digestive systems are filled with air. Dolania americana has
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#17327808482471752-401: A pair of segmented palps. The mouthparts and rest of the head can be articulated in at least three different positions: prognathous, opisthognathous, and hypognathous. In species with prognathous articulation, the head is vertically aligned with the body, such as species of Formicidae ; while in a hypognathous type, the head is aligned horizontally adjacent to the body. An opisthognathous head
1898-404: A posterior concave branch. The convex or concave nature of the veins has been used as evidence in determining the identities of the persisting distal branches of the veins of modern insects, but it has not been demonstrated to be consistent for all wings. Wing areas are delimited and subdivided by fold lines , along which the wings can fold, and flexion lines , which flex during flight. Between
2044-426: A reticulum as in the wings of Odonata (dragonflies and damselflies) and at the base of the forewings of Tettigonioidea and Acridoidea (katydids and grasshoppers, respectively). The archedictyon is the name given to a hypothetical scheme of wing venation proposed for the very first winged insect. It is based on a combination of speculation and fossil data. Since all winged insects are believed to have evolved from
2190-426: A sandwich pattern, while the exocuticle is rigid and sclerotized . The exocuticle is greatly reduced in many soft-bodied insects, especially the larval stages (e.g., caterpillars ). Chemically, chitin is a long-chain polymer of a N-acetylglucosamine , a derivative of glucose. In its unmodified form, chitin is translucent, pliable, and resilient. In arthropods , however, it is often modified, becoming embedded in
2336-644: A scarcity of predacious nymphs can result in an over-abundance of their prey species. Fish that feed on mayfly nymphs that have bioaccumulated heavy metals are themselves at risk. Adult female mayflies find water by detecting the polarization of reflected light. They are easily fooled by other polished surfaces which can act as traps for swarming mayflies. The threat to mayflies applies also to their eggs. "Modest levels" of pollution in rivers in England are sufficient to kill 80% of mayfly eggs, which are as vulnerable to pollutants as other life-cycle stages; numbers of
2482-594: A single compound eye of, for example, large dragonflies. This type of eye gives less resolution than eyes found in vertebrates, but it gives an acute perception of movement and usually possesses UV- and green sensitivity, and may have additional sensitivity peaks in other regions of the visual spectrum. Often an ability to detect the E-vector of polarized light exists in polarization of light. There can also be an additional two or three ocelli, which help detect low light or small changes in light intensity. The image perceived
2628-429: A small vein, the precosta, is sometimes found above the costa. In almost all extant insects, the precosta is fused with the costa; the costa rarely ever branches because it is at the leading edge, which is associated at its base with the humeral plate. The trachea of the costal vein is perhaps a branch of the subcostal trachea. Located after the costa is the third vein, the subcosta, which branches into two separate veins:
2774-406: A variety of different sclerites and sutures, varying greatly from order to order, and they will not be discussed in detail in this section. Most phylogenetically advanced insects have two pairs of wings located on the second and third thoracic segments. Insects are the only invertebrates to have developed flight capability, and this has played an important part in their success. Insect flight
2920-407: A vein forks there is always an interpolated vein of the opposite position between the two branches. The concave vein will fork into two concave veins (with the interpolated vein being convex) and the regular alteration of the veins is preserved. The veins of the wing appear to fall into an undulating pattern according to whether they tend to fold up or down when the wing is relaxed. The basal shafts of
3066-402: A very few species the gills are instead located on the coxae of the legs, or the bases of the maxillae. The abdomen terminates in slender thread-like projections, consisting of a pair of cerci , with or without a third central caudal filament . The final moult of the nymph is not to the full adult form, but to a winged stage called a subimago that physically resembles the adult, but which
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#17327808482473212-452: A very short time and is known as a subimago, or to fly fishermen as a dun. Mayflies at the subimago stage are a favourite food of many fish, and many fishing flies are modelled to resemble them. The subimago stage does not survive for long, rarely for more than 24 hours. In some species, it may last for just a few minutes, while the mayflies in the family Palingeniidae have sexually mature subimagos and no true adult form at all. Often, all
3358-427: A wide range of predators and form an important part of the aquatic food chain . Fish are among the main predators, picking nymphs off the bottom or ingesting them in the water column, and feeding on emerging nymphs and adults on the water surface. Carnivorous stonefly , caddisfly , alderfly and dragonfly larvae feed on bottom-dwelling mayfly nymphs, as do aquatic beetles, leeches, crayfish and amphibians . Besides
3504-422: Is a combination of inputs from the numerous ommatidia, located on a convex surface, thus pointing in slightly different directions. Compared with simple eyes , compound eyes possess very large view angles and better acuity than the insect's dorsal ocelli, but some stemmatal (= larval eyes), for example, those of sawfly larvae ( Tenthredinidae ) with an acuity of 4 degrees and very high polarization sensitivity, match
3650-433: Is a landmark on the posterior surface of the head, and is typically near the occipital foremen. In pterygotes, the postocciput forms the extreme posterior, often U-shaped, which forms the rim of the head extending to the postoccipital suture. In pterygotes, such as those of Orthoptera, the occipital foramen and the mouth are not separated. The three types of occipital closures, or points under the occipital foramen that separate
3796-423: Is a median lobe immediately behind the mouth, projecting forwards from the back of the preoral cavity; it is a lobe of uncertain origin, but perhaps associated with the mandibular segment; in apterygotes, earwigs, and nymphal mayflies, the hypopharynx bears a pair of lateral lobes, the superlinguae (singular: superlingua). It divides the cavity into a dorsal food pouch, or cibarium, and a ventral salivarium into which
3942-428: Is a tendency for the eggs and nymphs to get washed downstream. To counteract this, females may fly upriver before depositing their eggs. For example, the female Tisza mayfly , the largest European species with a length of 12 cm (4.7 in), flies up to 3 kilometres (2 mi) upstream before depositing eggs on the water surface. These sink to the bottom and hatch after 45 days, the nymphs burrowing their way into
4088-434: Is between the compound eyes, clypeus, and mouthparts. The postgena is the area immediately posteriad, or posterior or lower on the gena of pterygote insects , and forms the lateral and ventral parts of the occipital arch. The occipital arch is a narrow band forming the posterior edge of the head capsule arching dorsally over the foramen. The subgenal area is usually narrow, located above the mouthparts; this area also includes
4234-405: Is called the tergum (or notum, to distinguish it from the abdominal terga). The two lateral regions are called the pleura (singular: pleuron), and the ventral aspect is called the sternum. In turn, the notum of the prothorax is called the pronotum, the notum for the mesothorax is called the mesonotum and the notum for the metathorax is called the metanotum. Continuing with this logic, there are also
4380-477: Is continuously sclerotized with the latter. The cubitus, the sixth vein of the wing, is primarily two-branched. The primary forking takes place near the base of the wing, forming the two principal branches (Cu1, Cu2). The anterior branch may break up into several secondary branches, but commonly it forks into two distal branches. The second branch of the cubitus (Cu2) in Hymenoptera, Trichoptera, and Lepidoptera,
4526-435: Is innervated by the tritocerebrum of the brain, which is the fused ganglia of the third head segment. This is formed from the fusion of parts of a pair of ancestral appendages found on the third head segment, showing their relationship. Its ventral, or inner, surface is usually membranous and forms the lobe-like epipharynx, which bears mechanosensilla and chemosensilla. Chewing insects have two mandibles, one on each side of
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4672-438: Is inwardly concave, thus forming a central tube through which moisture is sucked. Suction is affected by the contraction and expansion of a sac in the head. The proboscis is coiled under the head when the insect is at rest and is extended only when feeding. The maxillary palpi are reduced or even vestigial. They are conspicuous and five-segmented in some of the more basal families and are often folded. The shape and dimensions of
4818-622: Is long and roughly cylindrical, with ten segments and two or three long cerci (tail-like appendages) at the tip. Like Entognatha , Archaeognatha and Zygentoma , the spiracles on the abdomen don't have closing muscles. Uniquely among insects, mayflies possess paired genitalia, with the male having two aedeagi (penis-like organs) and the female two gonopores (sexual openings). Mayflies are hemimetabolous (they have "incomplete metamorphosis "). They are unique among insects in that they moult one more time after acquiring functional wings; this last-but-one winged ( alate ) instar usually lives
4964-450: Is longitudinally placed on the vertex, separating the epicranial halves of the head to the left and right sides. Depending on the insect, the suture may come in different shapes: like either a Y, U or V. Those diverging lines that make up the ecdysial suture are called the frontal or frontogenal sutures. Not all species of insects have frontal sutures, but in those that do, the sutures split open during ecdysis , which provides an opening for
5110-417: Is not helpful. In the anatomy of some taxa, such as many Cicadomorpha , the front of the head is fairly clearly distinguished and tends to be broad and sub-vertical; that median area commonly is taken to be the frons. The clypeus is a sclerite between the face and labrum, which is dorsally separated from the frons by the frontoclypeal suture in primitive insects. The clypeogenal suture laterally demarcates
5256-571: Is not very well understood, relying on turbulent aerodynamic effects. The primitive insect groups use muscles that act directly on the wing structure. The more advanced groups making up the Neoptera have foldable wings, and their muscles act on the thorax wall and power the wings indirectly. These muscles can contract multiple times for each single nerve impulse, allowing the wings to beat faster than would ordinarily be possible. Insect flight can be rapid, maneuverable, and versatile, possibly due to
5402-551: Is part of an ancient group of insects termed the Palaeoptera , which also contains dragonflies and damselflies . Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families . Mayflies have ancestral traits that were probably present in the first flying insects, such as long tails and wings that do not fold flat over the abdomen . Their immature stages are aquatic fresh water forms (called "naiads" or " nymphs "), whose presence indicates
5548-485: Is positioned diagonally, such as in species of Blattodea and some Coleoptera . The mouthparts vary greatly between insects of different orders, but the two main functional groups are mandibulate and haustellate. Haustellate mouthparts are used for sucking liquids and can be further classified by the presence of stylets , which include piercing-sucking, sponging, and siphoning. The stylets are needle-like projections used to penetrate plant and animal tissues. The stylets and
5694-444: Is reabsorbed. In molting, the old cuticle separates from the epidermis ( apolysis ). Enzymatic molting fluid is then released between the old cuticle and epidermis, which separates the exocuticle by digesting the endocuticle and sequestering its material for the new cuticle. When the new cuticle has formed sufficiently, the epicuticle and reduced exocuticle are shed in ecdysis . The four principal regions of an insect body segment are
5840-590: Is represented in the fossil record by the Ypresian species N. antiqua from Washington state . Grimaldi and Engel, reviewing the phylogeny in 2005, commented that many cladistic studies had been made with no stability in Ephemeroptera suborders and infraorders; the traditional division into Schistonota and Pannota was wrong because Pannota is derived from the Schistonota. The phylogeny of
5986-416: Is similar in structure to the maxilla , but with the appendages of the two sides fused by the midline, so they come to form a median plate. The basal part of the labium, equivalent to the maxillary cardines and possibly including a part of the sternum of the labial segment, is called the postmentum. This may be subdivided into a proximal submentum and a distal mentum. Distal to the postmentum, and equivalent to
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6132-540: Is the dominant life history stage of the mayfly. Different insect species vary in their tolerance to water pollution, but in general, the larval stages of mayflies, stoneflies (Plecoptera) and caddis flies (Trichoptera) are susceptible to a number of pollutants including sewage , pesticides and industrial effluent . In general, mayflies are particularly sensitive to acidification , but tolerances vary, and certain species are exceptionally tolerant to heavy metal contamination and to low pH levels. Ephemerellidae are among
6278-406: Is the study and description of the physical form of insects . The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insects from other arthropods: they have a body divided into three regions (called tagmata) (head, thorax, and abdomen), three pairs of legs, and mouthparts located outside of
6424-606: Is usually sexually immature and duller in colour. The subimago, or dun, often has partially cloudy wings fringed with minute hairs known as microtrichia; its eyes, legs and genitalia are not fully developed. Females of some mayflies (subfamily Palingeniinae) do not moult from a subimago state into an adult stage and are sexually mature while appearing like a subimago with microtrichia on the wing membrane. Oligoneuriine mayflies form another exception in retaining microtrichia on their wings but not on their bodies. Subimagos are generally poor fliers, have shorter appendages, and typically lack
6570-458: Is usually triangular in shape, and its veins typically spread out from the third axillary like the ribs of a fan. Some of the vannal veins may be branched, and secondary veins may alternate with the primary veins. The vannal region is usually best developed in the hindwing, in which it may be enlarged to form a sustaining surface, as in Plecoptera and Orthoptera. The great fan-like expansions of
6716-400: Is usually unbranched; primitively, it is two-branched. The vannal veins (lV to nV) are the anal veins immediately associated with the third axillary, and are directly affected by the movement of this sclerite that brings about the flexion of the wings. In number, the vannal veins vary from one to 12, according to the expansion of the vannal area of the wing. The vannal tracheae usually arise from
6862-488: The Lower Cretaceous Crato Formation of Brazil also belongs as the last offshoot to Permoplectoptera. The Crato outcrops otherwise yielded fossil specimens of modern mayfly families or the extinct (but modern) family Hexagenitidae. However, from the same locality the strange larvae and adults of the extinct family Mickoleitiidae (order Coxoplectoptera ) have been described, which represents
7008-604: The Neotropical realm , while the Holarctic has a smaller number of genera but a high degree of speciation. Some thirteen families are restricted to a single bioregion . The main families have some general habitat preferences: the Baetidae favour warm water; the Heptageniidae live under stones and prefer fast-flowing water; and the relatively large Ephemeridae make burrows in sandy lake or river beds. The nymph
7154-412: The blue-winged olive mayfly ( Baetis ) have fallen dramatically, almost to none in some rivers. The major pollutants thought to be responsible are fine sediment and phosphate from agriculture and sewage. The status of many species of mayflies is unknown because they are known from only the original collection data. Four North American species are believed to be extinct. Among these, Pentagenia robusta
7300-441: The cuticle , consists of two layers; the epicuticle , which is a thin, waxy, water-resistant outer layer that lacks chitin, and the layer under it is called the procuticle . This is chitinous and much thicker than the epicuticle and has two layers, the outer is the exocuticle while the inner is the endocuticle. The tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, crisscrossing each other in
7446-415: The exuviae (cast skin) and then flies upwards, and in some, the nymph climbs out of the water before transforming. Nymphs live primarily in streams under rocks, in decaying vegetation or in sediments. Few species live in lakes, but they are among the most prolific. For example, the emergence of one species of Hexagenia was recorded on Doppler weather radar by the shoreline of Lake Erie in 2003. In
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#17327808482477592-548: The head capsule . This position of the mouthparts divides them from their closest relatives, the non-insect hexapods , which include Protura , Diplura , and Collembola . There is enormous variation in body structure amongst insect species. Individuals can range from 0.3 mm ( fairyflies ) to 30 cm across ( great owlet moth ); have no eyes or many; well-developed wings or none; and legs modified for running, jumping, swimming, or even digging. These modifications allow insects to occupy almost every ecological niche except
7738-406: The honey bee ( Hymenoptera : Apidae : Apis mellifera ), the elongated and fused labial glossae form a hairy tongue, which is surrounded by the maxillary galeae and the labial palps to form a tubular proboscis containing a food canal. In feeding, the tongue is dipped into the nectar or honey, which adheres to the hairs, and then is retracted so the adhering liquid is carried into the space between
7884-409: The hypostoma and pleurostoma . The vertex extends anteriorly above the bases of the antennae as a prominent, pointed, concave rostrum. The posterior wall of the head capsule is penetrated by a large aperture, the foramen. Through it passes the organ systems, such as the nerve cord , esophagus , salivary ducts , and musculature , connecting the head with the thorax . On the posterior aspect of
8030-593: The tergum or dorsal, sternum or ventral, and the two pleura or laterals. Hardened plates in the exoskeleton are called sclerites, which are subdivisions of the major regions – tergites, sternites, and pleurites, for respective regions tergum, sternum, and pleuron. The head in most insects is enclosed in a hard, heavily sclerotized, exoskeletal head capsule . The main exception is in those species whose larvae are not fully sclerotized, mainly some holometabola; but even most unsclerotized or weakly sclerotized larvae tend to have well-sclerotized head capsules, for example,
8176-651: The Ephemeroptera was first studied using molecular analysis by Ogden and Whiting in 2005. They recovered the Baetidae as sister to the other clades. Mayfly phylogeny was further studied using morphological and molecular analyses by Ogden and others in 2009. They found that the Asian genus Siphluriscus was sister to all other mayflies. Some existing lineages such as Ephemeroidea , and families such as Ameletopsidae, were found not to be monophyletic , through convergence among nymphal features. The following traditional classification, with two suborders Pannota and Schistonota ,
8322-446: The abdomen tilted upwards. Females fly into these swarms, and mating takes place in the air. A rising male clasps the thorax of a female from below using his front legs bent upwards, and inseminates her. Copulation may last just a few seconds, but occasionally a pair remains in tandem and flutters to the ground. Males may spend the night in vegetation and return to their dance the following day. Although they do not feed, some briefly touch
8468-529: The addition of zinc, manganese, or rarely, iron, in amounts up to about 4% of the dry weight. They are typically the largest mouthparts of chewing insects, being used to masticate (cut, tear, crush, chew) food items. They open outwards (to the sides of the head) and come together medially. In carnivorous, chewing insects, the mandibles can be modified to be more knife-like, whereas in herbivorous chewing insects, they are more typically broad and flat on their opposing faces (e.g., caterpillars ). In male stag beetles ,
8614-407: The anal area can be folded like a fan. The four different fields found on insect wings are: Most veins and cross-veins occur in the anterior area of the remigium , which is responsible for most of the flight, powered by the thoracic muscles. The posterior portion of the remigium is sometimes called the clavus; the two other posterior fields are the anal and jugal areas . When the vannal fold has
8760-478: The antecostal sutures, marking the primary intersegmental folds between segments; phragmata provide attachment for the longitudinal flight muscles. Each alinotum (sometimes confusingly referred to as a "notum") may be traversed by sutures that mark the position of internal strengthening ridges and commonly divide the plate into three areas: the anterior prescutum, the scutum, and the smaller posterior scutellum. The lateral pleural sclerites are believed to be derived from
8906-436: The antennae is also quite variable, but the first segment (the one attached to the head) is always called the scape, and the second segment is called the pedicel. The remaining antennal segments or flagellomeres are called the flagellum. General insect antenna types are shown below: The insect mouthparts consist of the maxilla, labium, and in some species, the mandibles. The labrum is a simple, fused sclerite, often called
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#17327808482479052-463: The anterior and posterior. The base of the subcosta is associated with the distal end of the neck of the first axillary. The fourth vein is the radius, which is branched into five separate veins. The radius is generally the strongest vein of the wing. Toward the middle of the wing, it forks into a first undivided branch (R1) and a second branch, called the radial sector (Ra), which subdivides dichotomously into four distal branches (R2, R3, R4, R5). Basally,
9198-407: The blood from clotting. And finally, the labrum (upper lip) is used to suck up the blood. Species of the genus Anopheles are characterized by their long palpi (two parts with widening end), almost reaching the end of labrum. The proboscis is formed from maxillary galeae and is an adaption found in some insects for sucking. The muscles of the cibarium or pharynx are strongly developed and form
9344-484: The brief life of a daily newspaper with that of a mayfly in the satirical poem "The Newspaper" (1785), both being known as "ephemera". Immature mayflies are aquatic and are referred to as nymphs or naiads. In contrast to their short lives as adults, they may live for several years in the water. They have an elongated, cylindrical or somewhat flattened body that passes through a number of instars (stages), moulting and increasing in size each time. When ready to emerge from
9490-420: The cardo, and ventral adductor muscles arising on the tentorium are inserted on both the cardo and stipes. Arising in the stipes are flexor muscles of the lacinea and galea and another lacineal flexor arises in the cranium, but neither the lacinea nor the galea has an extensor muscle. The palp has levator and depressor muscles arising in the stipes, and each segment of the palp has a single muscle causing flexion of
9636-416: The changing shape, extraordinary control, and variable motion of the insect wing. Insect orders use different flight mechanisms; for example, the flight of a butterfly can be explained using steady-state, nontransitory aerodynamics , and thin airfoil theory. Each of the wings consists of a thin membrane supported by a system of veins. The membrane is formed by two layers of integument closely apposed, while
9782-495: The clypeus, with the clypeus ventrally separated from the labrum by the clypeolabral suture. The clypeus differs in shape and size, such as species of Lepidoptera with a large clypeus with elongated mouthparts. The cheek or gena forms the sclerotized area on each side of the head below the compound eyes extending to the gular suture. Like many parts making up the insect's head, the gena varies among species, with its boundaries difficult to establish. In dragonflies and damselflies , it
9928-439: The clypeus. Laterally it is limited by the fronto-genal sulcus, if present, and the boundary with the vertex, by the ecdysial cleavage line, if it is visible. If there is a median ocellus, it generally is on the frons, though in some insects such as many Hymenoptera, all three ocelli appear on the vertex. A more formal definition is that it is the sclerite from which the pharyngeal dilator muscles arise, but in many contexts that too,
10074-415: The colour patterns used to attract mates. In males of Ephoron leukon , the subimagos have forelegs that are short and compressed, with accordion like folds, and expands to more than double its length after moulting. After a period, usually lasting one or two days but in some species only a few minutes, the subimago moults to the full adult form, making mayflies the only insects where a winged form undergoes
10220-419: The deep ocean. This article describes the basic insect body and some variations of the different body parts; in the process, it defines many of the technical terms used to describe insect bodies. Insects, like all arthropods, have no interior skeleton; instead, they have an exoskeleton , a hard outer layer made mostly of chitin that protects and supports the body. The insect body is divided into three parts :
10366-530: The direct mortality caused by these predators, the behaviour of their potential prey is also affected, with the nymphs' growth rate being slowed by the need to hide rather than feed. The nymphs are highly susceptible to pollution and can be useful in the biomonitoring of water bodies. Once they have emerged, large numbers are preyed on by birds, bats and by other insects, such as Rhamphomyia longicauda . Mayfly nymphs may serve as hosts for parasites such as nematodes and trematodes . Some of these affect
10512-407: The external cuticle and an internal basement membrane. The majority of insect material is inside of the endocuticle. The cuticle provides muscular support and acts as a protective shield as the insect develops. However, since it cannot grow, the external sclerotized part of the cuticle is periodically shed in a process called "molting". As the time for molting approaches, most of the exocuticle material
10658-404: The external organs of the respiratory system, are found on the pterothorax, usually one between the pro- and mesopleoron, as well as one between the meso- and metapleuron. The ventral view or sternum follows the same convention, with the prosternum under the prothorax, the mesosternum under the mesothorax and the metasternum under the metathorax. The notum, pleura, and sternum of each segment have
10804-454: The eyes. The mouthparts are designed for chewing and consist of a flap-like labrum , a pair of strong mandibles , a pair of maxillae , a membranous hypopharynx and a labium . The thorax consists of three segments – the hindmost two, the mesothorax and metathorax , being fused. Each segment bears a pair of legs which usually terminate in a single claw. The legs are robust and often clad in bristles, hairs or spines. Wing pads develop on
10950-667: The family is † Amerogenia from the Late Cretaceous ( Turonian ) aged New Jersey amber . Mayfly See text Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States , as Canadian soldiers in the American Great Lakes region , and as up-winged flies in the United Kingdom) are aquatic insects belonging to the order Ephemeroptera . This order
11096-406: The feeding tube form the modified mandibles, maxilla, and hypopharynx. Mandibular mouthparts are found in species of Odonata , adult Neuroptera , Coleoptera , Hymenoptera , Blattodea , Orthoptera , and Lepidoptera . However, most adult Lepidoptera have siphoning mouthparts, while their larvae (commonly called caterpillars ) have mandibles . The labrum is a broad lobe forming the roof of
11242-916: The female submerges and places the eggs among plants or in crevices underwater, but in general, they sink to the bottom. The incubation time is variable, depending at least in part on temperature, and may be anything from a few days to nearly a year. Eggs can go into a quiet dormant phase or diapause . The larval growth rate is also temperature-dependent, as is the number of moults . At anywhere between ten and fifty, these post-embryonic moults are more numerous in mayflies than in most other insect orders. The nymphal stage of mayflies may last from several months to several years, depending on species and environmental conditions. Around half of all mayfly species whose reproductive biology has been described are parthenogenetic (able to asexually reproduce), including both partially and exclusively parthenogenetic populations and species. Many species breed in moving water, where there
11388-547: The fine hairs ( setae ) that cover them. However, touch is not the only thing that antennae can detect; numerous tiny sensory structures on the antennae allow insects to sense smells, temperature, humidity, pressure, and even potentially sense themselves in space . Some insects, including bees and some groups of flies, can also detect sound with their antennae. The number of segments in an antenna varies amongst insects, with higher flies having 3-6 segments, while adult cockroaches can have over 140. The general shape of
11534-410: The first vannal vein. In the cicada, the vannal fold lies immediately behind the first vannal vein (lV). These small variations in the actual position of the vannal fold, however, do not affect the unity of action of the vannal veins, controlled by the flexor sclerite (3Ax), in the flexion of the wing. In the hindwings of most Orthoptera, a secondary vena dividens forms a rib in the vannal fold. The vannus
11680-437: The flexion and the fold lines, the fundamental distinction is often blurred, as fold lines may permit some flexibility or vice versa. Two constants, found in nearly all insect wings, are the claval (a flexion line) and jugal folds (or fold line), forming variable and unsatisfactory boundaries. Wing folding can be very complicated, with transverse folding occurring in the hindwings of Dermaptera and Coleoptera, and in some insects,
11826-401: The food chain. Mayflies are distributed all over the world in clean freshwater habitats, though absent from Antarctica. They tend to be absent from oceanic islands or represented by one or two species that have dispersed from nearby mainland. Female mayflies may be dispersed by wind, and eggs may be transferred by adhesion to the legs of waterbirds. The greatest generic diversity is found in
11972-580: The fossil sister group of modern mayflies, even though they had very peculiar adaptations such as raptorial forelegs. The oldest mayfly inclusion in amber is Cretoneta zherichini (Leptophlebiidae) from the Lower Cretaceous of Siberia . In the much younger Baltic amber numerous inclusions of several modern families of mayflies have been found (Ephemeridae, Potamanthidae, Leptophlebiidae, Ametropodidae, Siphlonuridae, Isonychiidae, Heptageniidae, and Ephemerellidae). The modern genus Neoephemera
12118-413: The fused maxillary stipites, is the prementum. The prementum closes the preoral cavity from behind. Terminally, it bears four lobes, two inner glossae, and two outer paraglossae, which are collectively known as the ligula. One or both pairs of lobes may be absent or they may be fused to form a single median process. A palp arises from each side of the prementum, often being three-segmented. The hypopharynx
12264-450: The galeae and labial palps. This back-and-forth glossal movement occurs repeatedly. Movement of liquid to the mouth results from the action of the cibarial pump, facilitated by each retraction of the tongue pushing liquid up the food canal either for feeding requirements or to have a suitable media for laying their egg. The insect thorax has three segments: the prothorax , mesothorax , and metathorax . The anterior segment, closest to
12410-417: The genus Isonychia . The nymph have forelegs that contain long bristle-like structures that have two rows of hairs. Interlocking hairs form the filter by which the insect traps food particles. The action of filter feeding has a small impact on water purification but an even larger impact on the convergence of small particulate matter into matter of a more complex form that goes on to benefit consumers later in
12556-400: The group of vannal tracheae. In the mature wings of more generalized insects, the postcubitus is always associated proximally with the cubitus and is never intimately connected with the flexor sclerite (3Ax) of the wing base. In Neuroptera, Mecoptera, and Trichoptera, the postcubitus may be more closely associated with the vannal veins, but its base is always free from the latter. The postcubitus
12702-403: The head and inserted on the posterior lateral margins on two small sclerites, the tormae, and, at least in some insects, by a resilin spring in the cuticle at the junction of the labrum with the clypeus. Until recently, the labrum generally was considered to be associated with the first head segment. However, recent studies of the embryology, gene expression, and nerve supply to the labrum show it
12848-470: The head and mesothorax. Because the mesothorax and metathorax hold the wings, they have a combined name called the pterothorax (pteron = wing). The forewing, which goes by different names in different orders (e.g., the tegmina in Orthoptera and elytra in Coleoptera), arises between the mesonotum and the mesopleuron, and the hindwing articulates between the metanotum and metapleuron. The legs arise from
12994-453: The head are the occiput , postgena , occipital foramen , posterior tentorial pit , gula, postgenal bridge , hypostomal suture and bridge , and the mandibles , labium , and maxilla . The occipital suture is well-founded in species of Orthoptera, but not so much in other orders. Where found, the occipital suture is the arched, horseshoe-shaped groove on the back of the head ending at the posterior of each mandible. The postoccipital suture
13140-542: The head, thorax , and abdomen . The head is specialized for sensory input and food intake; the thorax, which is the anchor point for the legs and wings (if present), is specialized for locomotion; and the abdomen is for digestion , respiration , excretion , and reproduction. Although the general function of the three body regions is the same across all insect species, there are major differences in basic structure, with wings, legs, antennae , and mouthparts being variable from group to group. The insect's outer skeleton,
13286-469: The head, is the prothorax; its major features are the first pair of legs and the pronotum . The middle segment is the mesothorax; its major features are the second pair of legs and the anterior wings, if any. The third, the posterior , thoracic segment, abutting the abdomen, is the metathorax, which bears the third pair of legs and the posterior wings. Each segment is delineated by an intersegmental suture. Each segment has four basic regions. The dorsal surface
13432-524: The head. The mandibles are positioned between the labrum and maxillae . The mandibles cut and crush food, and may be used for defense; generally, they have an apical cutting edge, and the more basal molar area grinds the food. They can be extremely hard (around 3 on Mohs , or an indentation hardness of about 30 kg/mm ); thus, many termites and beetles have no physical difficulty in boring through foils made from such common metals as copper, lead, tin, and zinc. The cutting edges are typically strengthened by
13578-484: The hindwings of Acrididae are clearly the vannal regions, since their veins are all supported on the third axillary sclerites on the wing bases, though Martynov (1925) ascribes most of the fan areas in Acrididae to the jugal regions of the wings. The true jugum of the acridid wing is represented only by the small membrane (Ju) mesad of the last vannal vein. The jugum is more highly developed in some other Orthoptera, as in
13724-548: The individuals in a population mature at once (a hatch), and for a day or two in the spring or autumn, mayflies are extremely abundant, dancing around each other in large groups, or resting on every available surface. In many species the emergence is synchronised with dawn or dusk, and light intensity seems to be an important cue for emergence, but other factors may also be involved. Baetis intercalaris , for example, usually emerges just after sunset in July and August, but in one year,
13870-462: The labial palps have become modified to form the labellum, and the maxillary palps are present, although sometimes short. In Brachycera, the labellum is especially prominent and used for sponging liquid or semiliquid food. The labella are a complex structure consisting of many grooves, called pseudotracheae, which sop up liquids. Salivary secretions from the labella assist in dissolving and collecting food particles so they can be more easily taken up by
14016-949: The large blue lake mayfly, which is a native of Australia and is listed as endangered because its alpine habitat is vulnerable to climate change . Ephemeroptera was defined by Alpheus Hyatt and Jennie Maria Arms Sheldon in 1890–1. The taxonomy of the Ephemeroptera was reworked by George F. Edmunds and Jay R Traver , starting in 1954. Traver contributed to the 1935 work The Biology of Mayflies , and has been called "the first Ephemeroptera specialist in North America". As of 2012, over 3,000 species of mayfly in 42 families and over 400 genera are known worldwide, including about 630 species in North America . Mayflies are an ancient group of winged (pterygote) insects. Putative fossil stem group representatives (e.g. Syntonopteroidea-like Lithoneura lameerrei ) are already known from
14162-426: The larvae of Coleoptera and Hymenoptera. The larvae of Cyclorrhapha however, tend to have hardly any head capsule at all. The head capsule bears most of the sensory organs, including the antennae, ocelli, and compound eyes, along with the mouthparts. In the adult insect, the head capsule appears unsegmented, though embryological studies show it to consist of six segments that bear the paired head appendages, including
14308-596: The late Carboniferous . The name Ephemeroptera is from the Greek ἐφήμερος, ephemeros "short-lived" (literally "lasting a day", cf. English " ephemeral "), and πτερόν, pteron , " wing ", referring to the brief lifespan of adults. The English common name is for the insect's emergence in or around the month of May in the UK. The name shadfly is from the Atlantic fish the shad , which runs up American East Coast rivers at
14454-416: The long-spurred Madagascan star orchid Angraecum sesquipedale . The mouthparts of insects that feed on fluids are modified in various ways to form a tube through which liquid can be drawn into the mouth and usually another through which saliva passes. The muscles of the cibarium or pharynx are strongly developed to form a pump. In nonbiting flies, the mandibles are absent and other structures are reduced;
14600-431: The males have large compound eyes , but not divided into upper and lower parts. Heptageniids breed mainly in fast-flowing streams , but some species use still waters. The nymphs have a flattened shape and are usually dark in colour. They use a wide range of food sources with herbivorous , scavenging , and predatory species known. The Global Biodiversity Information Facility lists: The oldest described member of
14746-492: The mandibles are modified to such an extent as to not serve any feeding function but are instead used to defend mating sites from other males. In ants , the mandibles also serve a defensive function (particularly in soldier castes). In bull ants , the mandibles are elongated and toothed, used as hunting (and defensive) appendages. Situated beneath the mandibles, paired maxillae manipulate food during mastication . Maxillae can have hairs and "teeth" along their inner margins. At
14892-432: The mesopleura and metapleura, as well as the mesosternum and metasternum. The tergal plates of the thorax are simple structures in apterygotes and many immature insects but are variously modified in winged adults. The pterothoracic nota each have two main divisions: the anterior, wing-bearing alinotum and the posterior, phragma-bearing postnotum. Phragmata (singular: phragma) are plate-like apodemes that extend inwards below
15038-413: The mesopleuron and metapleura. The mesothorax and metathorax each have a pleural suture (mesopleural and metapleural sutures) that runs from the wing base to the coxa of the leg. The sclerite anterior to the pleural suture is called the episternum (serially, the mesepisternum and metepisternum). The sclerite posterior to the suture is called the epimiron (serially, the mesepimiron and metepimiron). Spiracles,
15184-414: The mesothorax, and in some species, hindwing pads develop on the metathorax. The abdomen consists of ten segments, some of which may be obscured by a large pair of operculate gills, a thoracic shield (expanded part of the prothorax ) or the developing wing pads. In most taxa up to seven pairs of gills arise from the top or sides of the abdomen, but in some species they are under the abdomen, and in
15330-421: The mid-air mating. In the males of some families, there are two large cylindrical "turban" eyes (also known as turbanate or turbinate eyes) that face upwards in addition to the lateral eyes. They are capable of detecting ultraviolet light and are thought to be used during courtship to detect females flying above them. In some species all the legs are functionless, apart from the front pair in males. The abdomen
15476-557: The most famous English mayflies is Rhithrogena germanica , the fisherman's "March brown mayfly". The brief lives of mayfly adults have been noted by naturalists and encyclopaedists since Aristotle and Pliny the Elder in classical antiquity . The German engraver Albrecht Dürer included a mayfly in his 1495 engraving The Holy Family with the Mayfly to suggest a link between heaven and earth. The English poet George Crabbe compared
15622-436: The most tolerant groups and Siphlonuridae and Caenidae the least. The adverse effects on the insects of pollution may be either lethal or sub-lethal, in the latter case resulting in altered enzyme function, poor growth, changed behaviour or lack of reproductive success. As important parts of the food chain, pollution can cause knock-on effects to other organisms; a dearth of herbivorous nymphs can cause overgrowth of algae, and
15768-486: The mouthparts, each pair on a specific segment. Each such pair occupies one segment, though not all segments in modern insects bear any visible appendages. Of all the insect orders, Orthoptera displays the greatest variety of features found in the heads of insects, including the sutures and sclerites . Here, the vertex , or the apex (dorsal region), is situated between the compound eyes of insects with hypognathous and opisthognathous heads. In prognathous insects,
15914-428: The new instar to emerge from the integument. The frons is that part of the head capsule that lies ventrad or anteriad of the vertex. The frons varies in size relative to the insect, and in many species, the definition of its borders is arbitrary, even in some insect taxa that have well-defined head capsules. In most species, though, the frons is bordered at its anterior by the frontoclypeal or epistomal sulcus above
16060-420: The next segment. In mandibulate mouthparts, the labium is a quadrupedal structure, although it is formed from two fused secondary maxillae. It can be described as the floor of the mouth. With the maxillae, it assists with the manipulation of food during mastication or chewing or, in the unusual case of the dragonfly nymph , extends out to snatch prey back to the head, where the mandibles can eat it. The labium
16206-484: The nymphs are herbivores or detritivores , feeding on algae , diatoms or detritus , but in a few species, they are predators of chironomid and other small insect larvae and nymphs. Nymphs of Povilla burrow into submerged wood and can be a problem for boat owners in Asia. Some are able to shift from one feeding group to another as they grow, thus enabling them to utilise a variety of food resources. They process
16352-438: The nymphs of most mayfly species, the paddle-like gills do not function as respiratory surfaces because sufficient oxygen is absorbed through the integument, instead serving to create a respiratory current. However, in low-oxygen environments such as the mud at the bottom of ponds in which Ephemera vulgata burrows, the filamentous gills act as true accessory respiratory organs and are used in gaseous exchange. In most species,
16498-426: The nymphs' behaviour in such a way that they become more likely to be predated. Other nematodes turn adult male mayflies into quasi-females which haunt the edges of streams, enabling the parasites to break their way out into the aqueous environment they need to complete their life cycles. The nymphs can also serve as intermediate hosts for the horsehair worm Paragordius varius , which causes its definitive host ,
16644-402: The outer margin, the galea is a cupped or scoop-like structure, which sits over the outer edge of the labium. They also have palps , which are used to sense the characteristics of potential foods. The maxillae occupy a lateral position, one on each side of the head behind the mandibles. The proximal part of the maxilla consists of a basal cardo, which has a single articulation with the head, and
16790-400: The performance of compound eyes. Because the individual lenses are so small, the effects of diffraction impose a limit on the possible resolution that can be obtained (assuming they do not function as phased arrays ). This can only be countered by increasing lens size and number. To see with a resolution comparable to our simple eyes, humans would require compound eyes that would each reach
16936-427: The preoral cavity, suspended from the clypeus in front of the mouth and forming the upper lip. On its inner side, it is membranous and may be produced into a median lobe, the epipharynx , bearing some sensilla . The labrum is raised away from the mandibles by two muscles arising in the head and inserted medially into the anterior margin of the labrum. It is closed against the mandibles in part by two muscles arising in
17082-451: The proboscis have evolved to give different species wider and therefore more advantageous diets. There is an allometric scaling relationship between the body mass of Lepidoptera and length of the proboscis from which an interesting adaptive departure is the unusually long-tongued hawk moth Xanthopan morganii praedicta . Charles Darwin predicted the existence and proboscis length of this moth before its discovery based on his knowledge of
17228-466: The proboscis, paired mandibles and maxillae. The maxillae form needle-like structures, called stylets , which are enclosed by the labium. When mosquito bites, maxillae penetrate the skin and anchor the mouthparts, thus allowing other parts to be inserted. The sheath-like labium slides back, and the remaining mouthparts pass through its tip and into the tissue. Then, through the hypopharynx, the mosquito injects saliva , which contains anticoagulants to stop
17374-459: The process of bioturbation. By burrowing in the bottom of lakes and redistributing nutrients, mayflies indirectly regulate phytoplankton and epibenthic primary production. Once burrowing to the bottom of the lake, mayfly nymphs begin to billow their respiratory gills. This motion creates current that carries food particles through the burrow and allows the nymph to filter feed. Other mayfly nymphs possess elaborate filter feeding mechanisms like that of
17520-433: The pseudotracheae or laid their egg on the suitable media; this is thought to occur by capillary action. The liquid food is then drawn up from the pseudotracheae through the food channel into the esophagus . The mouthparts of bees are of a chewing and lapping-sucking type. Lapping is a mode of feeding in which liquid or semiliquid food adhering to a protrusible organ, or "tongue", is transferred from substrate to mouth. In
17666-435: The pump. In Hemiptera and many Diptera, which feed on fluids within plants or animals, some components of the mouthparts are modified for piercing, and the elongated structures are called stylets. The combined tubular structures are referred to as the proboscis, although specialized terminology is used in some groups. In species of Lepidoptera, it consists of two tubes held together by hooks and separable for cleaning. Each tube
17812-454: The radial cross-vein (r) between R and the first fork of Rs, the sectorial cross-vein (s) between the two forks of R8, the median cross-vein (m-m) between M2 and M3, and the mediocubital cross-vein (m-cu) between the media and the cubitus. The veins of insect wings are characterized by a convex-concave placement, such as those seen in mayflies (i.e., concave is "down" and convex is "up"), which alternate regularly and by their branching; whenever
17958-428: The radius is flexibly united with the anterior end of the second axillary (2Ax). The fifth vein of the wing is the media. In the archetype pattern (A), the media forks into two main branches, a media anterior (MA), which divides into two distal branches (MA1, MA2), and a median sector, or media posterior (MP), which has four terminal branches (M1, M2, M3, M4). In most modern insects, the media anterior has been lost, and
18104-474: The salivary duct opens. It is commonly found fused to the libium. Most of the hypopharynx is membranous, but the adoral face is sclerotized distally, and proximally contains a pair of suspensory sclerites extending upwards to end in the lateral wall of the stomodeum. Muscles arising on the frons are inserted into these sclerites, which distally are hinged to a pair of lingual sclerites. These, in turn, have inserted into them antagonistic pairs of muscles arising on
18250-553: The same time as many mayflies emerge. From the Permian , numerous stem group representatives of mayflies are known, which are often lumped into a separate taxon Permoplectoptera (e.g. including Protereisma permianum in the Protereismatidae , and Misthodotidae ). The larvae of Permoplectoptera still had 9 pairs of abdominal gills, and the adults still had long hindwings. Maybe the fossil family Cretereismatidae from
18396-407: The sediment where they spend two or three years before hatching into subimagos. When ready to emerge, several different strategies are used. In some species, the transformation of the nymph occurs underwater and the subimago swims to the surface and launches itself into the air. In other species, the nymph rises to the surface, bursts out of its skin, remains quiescent for a minute or two resting on
18542-473: The shortest adult lifespan of any mayfly: the adult females of the species live for less than five minutes. Male adults may patrol individually, but most congregate in swarms a few metres above water with clear open sky above it, and perform a nuptial or courtship dance. Each insect has a characteristic up-and-down pattern of movement; strong wingbeats propel it upwards and forwards with the tail sloping down; when it stops moving its wings, it falls passively with
18688-435: The size of their heads. Compound eyes fall into two groups: apposition eyes, which form multiple inverted images, and superposition eyes, which form a single erect image. Compound eyes grow at their margins with the addition of new ommatidia. Antennae , sometimes called "feelers", are flexible appendages located on the insect's head which are used for sensing the environment. Insects can feel with their antennae because of
18834-425: The subcoxal segment of the ancestral insect leg. These sclerites may be separate, as in silverfish, or fused into an almost continuous sclerotic area, as in most winged insects. The pronotum of the prothorax may be simple in structure and small in comparison with the other nota, but in beetles, mantids, many bugs, and some Orthoptera, the pronotum is expanded, and in cockroaches, it forms a shield that covers part of
18980-402: The surface to drink a little water before flying off. Females typically lay between four hundred and three thousand eggs. The eggs are often dropped onto the surface of the water; sometimes the female deposits them by dipping the tip of her abdomen into the water during flight, releasing a small batch of eggs each time, or deposits them in bulk while standing next to the water. In a few species,
19126-505: The tentorium and labium. The various muscles serve to swing the hypopharynx forwards and back, and in the cockroach, two more muscles run across the hypopharynx and dilate the salivary orifice and expand the salivarium. Mouthparts can have multiple functions. Some insects combine piercing parts along with sponging ones which are then used to pierce through tissues of plants and animals. Female mosquitoes feed on blood ( hemophagous ) making them disease vectors. The mosquito mouthparts consist of
19272-561: The two lower halves of the postgena, are the hypostomal bridge, the postgenal bridge, and the gula. The hypostomal bridge is usually found in insects with hypognathous orientation. The postgenal bridge is found in the adults of species of higher Diptera and aculeate Hymenoptera , while the gula is found on some Coleoptera , Neuroptera , and Isoptera , which typically display prognathous-oriented mouthparts. Most insects have one pair of large, prominent compound eyes composed of units called ommatidia ( ommatidium , singular), up to 30,000 in
19418-409: The upper lip, and moves longitudinally. It is hinged to the clypeus. The mandibles (jaws) are a highly sclerotized pair of structures that move at right angles to the body, used for biting, chewing, and severing food. The maxillae are paired structures that can also move at right angles to the body and possess segmented palps. The labium (lower lip) is the fused structure that moves longitudinally and has
19564-542: The usual "media" is the four-branched media posterior with the common basal stem. In the Ephemerida, according to present interpretations of the wing venation, both branches of the media are retained, while in Odonata, the persisting media is the primitive anterior branch. The stem of the media is often united with the radius, but when it occurs as a distinct vein, its base is associated with the distal median plate (m') or
19710-419: The usual position anterior to the group of anal veins, the remigium contains the costal, subcostal, radial, medial, cubital, and postcubital veins. In the flexed wing, the remigium turns posteriorly on the flexible basal connection of the radius with the second axillary, and the base of the mediocubital field is folded medially on the axillary region along the plica basalis (bf) between the median plates (m, m') of
19856-445: The veins are convex, but each vein forks distally into an anterior convex branch and a posterior concave branch. Thus, the costa and subcosta are regarded as convex and concave branches of a primary first vein, Rs is the concave branch of the radius, posterior media is the concave branch of the media, Cu1 and Cu2 are respectively convex and concave, while the primitive postcubitus and the first vannal have each an anterior convex branch and
20002-404: The veins are formed where the two layers remain separate and the cuticle may be thicker and more heavily sclerotized. Within each of the major veins is a nerve and a trachea, and, since the cavities of the veins are connected with the hemocoel , hemolymph can flow into the wings. As the wing develops, the dorsal and ventral integumental layers become closely apposed over most of their area, forming
20148-410: The veins of the wing are subject to secondary forking and union by cross-veins. In some orders of insects, the cross-veins are so numerous, the whole venational pattern becomes a close network of branching veins and cross-veins. Ordinarily, however, a definite number of cross-veins having specific locations occurs. The more constant cross-veins are the humeral cross-vein (h) between the costa and subcosta,
20294-446: The venation may be reduced. In chalcidoid wasps , for instance, only the subcosta and part of the radius are present. Conversely, an increase in venation may occur by the branching of existing veins to produce accessory veins or by the development of additional, intercalary veins between the original ones, as in the wings of Orthoptera (grasshoppers and crickets). Large numbers of cross-veins are present in some insects, and they may form
20440-470: The vertex is not found between the compound eyes, but rather where the ocelli are normally found. This is because the primary axis of the head is rotated 90° to become parallel to the primary axis of the body. In some species, this region is modified and assumes a different name. The ecdysial suture is made of the coronal, frontal, and epicranial sutures plus the ecdysial and cleavage lines, which vary among different species of insects. The ecdysial suture
20586-411: The water, nymphs vary in length, depending on species, from 3 to 30 mm (0.12 to 1.18 in). The head has a tough outer covering of sclerotin , often with various hard ridges and projections; it points either forwards or downwards, with the mouth at the front. There are two large compound eyes , three ocelli (simple eyes) and a pair of antennae of variable lengths, set between or in front of
20732-400: The wing base. The vannus is bordered by the vannal fold, which typically occurs between the postcubitus and the first vannal vein. In Orthoptera, it usually has this position. In the forewing of Blattidae, however, the only fold in this part of the wing lies immediately before the postcubitus. In Plecoptera, the vannal fold is posterior to the postcubitus, but proximally it crosses the base of
20878-526: The wing membrane. The remaining areas form channels, the future veins, in which the nerves and tracheae may occur. The cuticle surrounding the veins becomes thickened and more heavily sclerotized to provide strength and rigidity to the wing. Hairs of two types may occur on the wings: microtrichia, which are small and irregularly scattered, and macrotrichia, which are larger, socketed, and may be restricted to veins. The scales of Lepidoptera and Trichoptera are highly modified macrotrichia. In some minuscule insects,
21024-517: Was introduced in 1979 by W. P. McCafferty and George F. Edmunds. The list is based on Peters and Campbell (1991), in Insects of Australia . Suborder Pannota Suborder Schistonota After Siphluriscidae Baetidae Baetiscidae Prosopistomatidae Coloburiscidae Leptophlebiidae Chromarcyidae Oligoneuriidae Vietnamellidae Austremerellidae Teloganodidae Insect morphology#Head Insect morphology
21170-470: Was mistaken by Comstock and Needham for the first anal. Proximally, the main stem of the cubitus is associated with the distal median plate (m') of the wing base. The postcubitus (Pcu) is the first anal of the Comstock and Needham system. The postcubitus, however, has the status of an independent wing vein and should be recognized as such. In nymphal wings, its trachea arises between the cubital trachea and
21316-617: Was originally collected from the Ohio River near Cincinnati , but this species has not been seen since its original collection in the 1800s. Ephemera compar is known from a single specimen, collected from the "foothills of Colorado" in 1873, but despite intensive surveys of the Colorado mayflies reported in 1984, it has not been rediscovered. The International Union for Conservation of Nature (IUCN) red list of threatened species includes one mayfly: Tasmanophlebia lacuscoerulei ,
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