40-516: Psocoptera ( / s oʊ ˈ k ɒ p t ər ə / ) are a paraphyletic group of insects that are commonly known as booklice , barklice or barkflies . The name Psocoptera has been replaced with Psocodea in recent literature, with the inclusion of the former order Phthiraptera into Psocodea (as part of the suborder Troctomorpha ). These insects first appeared in the Permian period, 295–248 million years ago. They are often regarded as
80-517: A bostrichid beetle. The adult is 4.0-4.5 mm long with ocelli on the head, antennae longer than the body, and developed wings. The hind legs are unusually long compared to other legs. Adults can live for 6-67 days under laboratory conditions, usually less than 40 days. Adult females start laying eggs as soon as 4 days after the final nymphal moult and they lay eggs singly on bark. Eggs are covered in crusts of fecal material similar in colour to bark, camouflaging them. It takes 20-26 days for
120-479: A "single common ancestor" organism. Paraphyly is common in speciation , whereby a mother species (a paraspecies ) gives rise to a daughter species without itself becoming extinct. Research indicates as many as 20 percent of all animal species and between 20 and 50 percent of plant species are paraphyletic. Accounting for these facts, some taxonomists argue that paraphyly is a trait of nature that should be acknowledged at higher taxonomic levels. Cladists advocate
160-592: A cell nucleus, a plesiomorphy ) from its excluded descendants. Also, some systematists recognize paraphyletic groups as being involved in evolutionary transitions, the development of the first tetrapods from their ancestors for example. Any name given to these hypothetical ancestors to distinguish them from tetrapods—"fish", for example—necessarily picks out a paraphyletic group, because the descendant tetrapods are not included. Other systematists consider reification of paraphyletic groups to obscure inferred patterns of evolutionary history. The term " evolutionary grade "
200-407: A common ancestor are said to be monophyletic . A paraphyletic group is a monophyletic group from which one or more subsidiary clades (monophyletic groups) are excluded to form a separate group. Philosopher of science Marc Ereshefsky has argued that paraphyletic taxa are the result of anagenesis in the excluded group or groups. A cladistic approach normally does not grant paraphyletic assemblages
240-480: A different shape to the thorax. Other, more subtle, variations are also known, such as changes to the development of the setae . The significance of such changes is uncertain, but their function appears to be different from similar variations in, for example, aphids . Like aphids, however, many psocids are parthenogenic , and the presence of males may even vary between different races of the same species. Psocids lay their eggs in minute crevices or on foliage, although
280-428: A few cases, some unicellular green algae ". Nymphs may leave the tunnel to browse on fungus on bark, but this seems to be a rare occurrence. Leaving the tunnel also occurs when a nymph moults. After moulting, a nymph may return to its original tunnel or move into a tunnel made by another. An unknown species of chalcidoid wasp parasitises P. mimulus nymphs and pupates within its tunnels. A white-coloured fungus
320-741: A few species are known to be viviparous . The young are born as miniature, wingless versions of the adult. These nymphs typically molt six times before reaching full adulthood. The total lifespan of a psocid is rarely more than a few months. Booklice range from approximately 1–2 millimetres ( 1 / 32 – 3 / 32 in). Some species are wingless and they are easily mistaken for bedbug nymphs and vice versa. Booklouse eggs take two to four weeks to hatch and can reach adulthood approximately two months later. Adult booklice can live for six months. Besides damaging books, they also sometimes infest food storage areas, where they feed on dry, starchy materials. Although some psocids feed on starchy household products,
360-419: A group of dinosaurs (part of Diapsida ), both of which are "reptiles". Osteichthyes , bony fish, are paraphyletic when circumscribed to include only Actinopterygii (ray-finned fish) and Sarcopterygii (lungfish, etc.), and to exclude tetrapods ; more recently, Osteichthyes is treated as a clade, including the tetrapods. The " wasps " are paraphyletic, consisting of the narrow-waisted Apocrita without
400-439: A kind of lizard). Put another way, viviparity is a synapomorphy for Theria within mammals, and an autapomorphy for Eulamprus tympanum (or perhaps a synapomorphy, if other Eulamprus species are also viviparous). Groupings based on independently-developed traits such as these examples of viviparity represent examples of polyphyly , not paraphyly. The following list recapitulates a number of paraphyletic groups proposed in
440-560: A more inclusive clade, it often makes sense to study the paraphyletic group that remains without considering the larger clade. For example, the Neogene evolution of the Artiodactyla (even-toed ungulates, like deer, cows, pigs and hippopotamuses - Cervidae , Bovidae , Suidae and Hippopotamidae , the families that contain these various artiodactyls, are all monophyletic groups) has taken place in environments so different from that of
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#1732780137450480-424: A phylogenetic species concept that does not consider species to exhibit the properties of monophyly or paraphyly, concepts under that perspective which apply only to groups of species. They consider Zander's extension of the "paraphyletic species" argument to higher taxa to represent a category error When the appearance of significant traits has led a subclade on an evolutionary path very divergent from that of
520-561: A psocid species, Psilopsocus mimulus , is the first known wood-boring psocopteran. These nymphs make their own burrows in woody material, rather than inhabiting vacated, existing burrows. This boring activity can create habitats that other organisms may use. Some species of psocids, such as Liposcelis bostrychophila , are common pests of stored products. Psocids, among other arthropods, have been studied to develop new pest control techniques in food manufacturing. One study found that modified atmospheres during packing (MAP) helped to control
560-556: A twig lacking a tunnel, a nymph bores into the end by eating through the central, softer wood. The consumed wood passes through the gut and is excreted as brown fecal pellets. To defecate, the nymph must first move backwards until the end of its abdomen protrudes from the tunnel. One actively burrowing nymph was observed producing fecal pellets every 20 minutes. Nymphs feeding within the tunnels produce black fecal pellets "consisting mainly of digested or partially digested fungal hyphae , fungal spores , woody and resinous material with, in
600-433: Is allowed as a synonym of Magnoliopsida. Phylogenetic analysis indicates that the monocots are a development from a dicot ancestor. Excluding monocots from the dicots makes the latter a paraphyletic group. Among animals, several familiar groups are not, in fact, clades. The order Artiodactyla ( even-toed ungulates ) as traditionally defined is paraphyletic because it excludes Cetaceans (whales, dolphins, etc.). Under
640-629: Is rather arbitrary, since the character states of common ancestors are inferences, not observations. These terms were developed during the debates of the 1960s and 1970s accompanying the rise of cladistics . Paraphyletic groupings are considered problematic by many taxonomists, as it is not possible to talk precisely about their phylogenetic relationships, their characteristic traits and literal extinction. Related terms are stem group , chronospecies , budding cladogenesis, anagenesis, or 'grade' groupings. Paraphyletic groups are often relics from outdated hypotheses of phylogenic relationships from before
680-436: Is said to be paraphyletic with respect to the excluded subgroups. In contrast, a monophyletic grouping (a clade ) includes a common ancestor and all of its descendants. The terms are commonly used in phylogenetics (a subfield of biology ) and in the tree model of historical linguistics . Paraphyletic groups are identified by a combination of synapomorphies and symplesiomorphies . If many subgroups are missing from
720-482: Is sometimes used for paraphyletic groups. Moreover, the concepts of monophyly , paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species. Current phylogenetic hypotheses of tetrapod relationships imply that viviparity , the production of offspring without the external laying of a fertilized egg, developed independently in the lineages that led to humans ( Homo sapiens ) and southern water skinks ( Eulampus tympanum ,
760-514: The Cetacea (whales, dolphins, and porpoises) that the Artiodactyla are often studied in isolation even though the cetaceans are a descendant group. The prokaryote group is another example; it is paraphyletic because it is composed of two Domains (Eubacteria and Archaea) and excludes (the eukaryotes ). It is very useful because it has a clearly defined and significant distinction (absence of
800-581: The ICN ) abandoned consideration of bacterial nomenclature in 1975; currently, prokaryotic nomenclature is regulated under the ICNB with a starting date of 1 January 1980 (in contrast to a 1753 start date under the ICBN/ICN). Among plants, dicotyledons (in the traditional sense) are paraphyletic because the group excludes monocotyledons . "Dicotyledon" has not been used as a botanic classification for decades, but
840-660: The ants and bees . The sawflies ( Symphyta ) are similarly paraphyletic, forming all of the Hymenoptera except for the Apocrita, a clade deep within the sawfly tree. Crustaceans are not a clade because the Hexapoda (insects) are excluded. The modern clade that spans all of them is the Tetraconata . One of the goals of modern taxonomy over the past fifty years has been to eliminate paraphyletic "groups", such as
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#1732780137450880-466: The maxilla is modified into a slender rod. This rod is used to brace the insect while it scrapes up detritus with its mandibles. They also have a swollen forehead, large compound eyes , and three ocelli . Their bodies are soft with a segmented abdomen. Some species can spin silk from glands in their mouth. They may festoon large sections of trunk and branches in dense swathes of silk. Some psocids have small ovipositors that are up to 1.5 times as long as
920-490: The abdomen. It bears antennae in which the first flagellar segment is slightly curved. There are wings buds held close to the sides of the thorax and abdomen. The abdomen is mostly weakly sclerotised except for the distal third, which is heavily sclerotised, black, almost cylindrical and appears unsegmented from above. The end of the abdomen is densely covered in short setae, most of which have the apex divided into several divergent points. This unique abdominal end resembles that of
960-407: The adults. This reflects their adaptation to a wood-boring lifestyle. First instar nymphs are mostly colourless except for the last two tergites , which are brown, heavily sclerotised and covered in long setae with slightly expanded tips. They have 8-segmented antennae that each have a broad basal segment. Later instars are different again. The head is almost as wide as the widest part of
1000-560: The eggs to hatch, starting the life cycle again. Psilopsocus mimulus has been known since 1963, but it was not until 1993 that its wood-boring habit was discovered. Nymphs of this species live in tunnels up to 6 cm long that run from the ends through the centres of pine twigs. They face away from the entrances of their tunnels and plug them using their sclerotised abdomens ( phragmosis ). Laboratory tests have confirmed that P. mimulus create their own tunnels in wood, as opposed to reusing tunnels left by other insects. If presented with
1040-450: The examples given here, from formal classifications. Species have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification. Some articulations of the phylogenetic species concept require species to be monophyletic, but paraphyletic species are common in nature, to the extent that they do not have a single common ancestor. Indeed, for sexually reproducing taxa, no species has
1080-480: The fact that a monophyletic group includes organisms consisting of all the descendants of a unique common ancestor. By comparison, the term polyphyly , or polyphyletic , uses the Ancient Greek prefix πολύς ( polús ), meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources. Groups that include all the descendants of
1120-441: The hindwings, and all four wings have a relatively simple venation pattern, with few cross-veins. The wings, if present, are held tent-like over the body. The legs are slender and adapted for jumping, rather than gripping, as in the true lice . The abdomen has nine segments, and no cerci . There is often considerable variation in the appearance of individuals within the same species. Many have no wings or ovipositors, and may have
1160-493: The island of Taiwan . Psilopsocus mimulus Psilopsocus mimulus is a species of bark louse in the family Psilopsocidae . Found in Australia , it is the first known member of its order to bore into wood. Like other Psocodea, P. mimulus has a life cycle consisting of egg, nymph and adult. Unlike other Psocodea, in which nymphs resemble smaller versions of adults, nymphs of P. mimulus are very different from
1200-622: The literature, and provides the corresponding monophyletic taxa. The concept of paraphyly has also been applied to historical linguistics , where the methods of cladistics have found some utility in comparing languages. For instance, the Formosan languages form a paraphyletic group of the Austronesian languages because they consist of the nine branches of the Austronesian family that are not Malayo-Polynesian and are restricted to
1240-411: The majority of psocids are woodland insects with little to no contact with humans, therefore they are of little economic importance. They are scavengers and do not bite humans. Psocids can affect the ecosystems in which they reside. Many psocids can affect decomposition by feeding on detritus, especially in environments with lower densities of predacious micro arthropods that may eat psocids. The nymph of
Psocoptera - Misplaced Pages Continue
1280-593: The most primitive of the hemipteroids . Their name originates from the Greek word ψῶχος ( psokhos ), meaning " gnawed " or " rubbed " and πτερά ( ptera ), meaning " wings ". There are more than 5,500 species in 41 families in three suborders. Many of these species have only been described in the early twenty-first century. They range in size from 1–10 millimetres ( 1 / 32 – 13 / 32 in) in length. The species known as booklice received their common name because they are commonly found amongst old books —they feed upon
1320-568: The named group, it is said to be polyparaphyletic. The term received currency during the debates of the 1960s and 1970s accompanying the rise of cladistics , having been coined by zoologist Willi Hennig to apply to well-known taxa like Reptilia ( reptiles ), which is paraphyletic with respect to birds . Reptilia contains the last common ancestor of reptiles and all descendants of that ancestor except for birds. Other commonly recognized paraphyletic groups include fish , monkeys , and lizards . The term paraphyly , or paraphyletic , derives from
1360-532: The order Psocodea . Here is a cladogram showing the relationships within Psocodea , with the former grouping Psocoptera highlighted: Phthiraptera Liposcelididae Pachytroctidae Sphaeropsocidae Amphientometae Psocomorpha Trogiomorpha Paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping
1400-410: The paste used in binding . The barklice are found on trees, feeding on algae and lichen . Psocids are small, scavenging insects with a relatively generalized body plan. They feed primarily on fungi, algae, lichen, and organic detritus in nature but are also known to feed on starch-based household items like grains, wallpaper glue and book bindings. They have chewing mandibles , and the central lobe of
1440-696: The ranks of the ICZN Code , the two taxa are separate orders. Molecular studies, however, have shown that the Cetacea descend from artiodactyl ancestors, although the precise phylogeny within the order remains uncertain. Without the Cetaceans the Artiodactyls are paraphyletic. The class Reptilia is paraphyletic because it excludes birds (class Aves ). Under a traditional classification, these two taxa are separate classes. However birds are sister taxon to
1480-471: The reoccurrence of pests during the manufacturing process and prevented further infestation in the final products that go to consumers. In the 2000s, morphological and molecular phylogenetic evidence has shown that the parasitic lice ( Phthiraptera ) evolved from within the psocopteran suborder Troctomorpha , thus making Psocoptera paraphyletic with respect to Phthiraptera. In modern systematics, Psocoptera and Phthiraptera are therefore treated together in
1520-567: The rise of cladistics. The prokaryotes (single-celled life forms without cell nuclei) are a paraphyletic grouping, because they exclude the eukaryotes , a descendant group. Bacteria and Archaea are prokaryotes, but archaea and eukaryotes share a common ancestor that is not ancestral to the bacteria. The prokaryote/eukaryote distinction was proposed by Edouard Chatton in 1937 and was generally accepted after being adopted by Roger Stanier and C.B. van Niel in 1962. The botanical code (the ICBN, now
1560-460: The status of "groups", nor does it reify them with explanations, as in cladistics they are not seen as the actual products of evolutionary events. A group whose identifying features evolved convergently in two or more lineages is polyphyletic (Greek πολύς [ polys ], "many"). More broadly, any taxon that is not paraphyletic or monophyletic can be called polyphyletic. Empirically, the distinction between polyphyletic groups and paraphyletic groups
1600-477: The two Ancient Greek words παρά ( pará ), meaning "beside, near", and φῦλον ( phûlon ), meaning "genus, species", and refers to the situation in which one or several monophyletic subgroups of organisms (e.g., genera, species) are left apart from all other descendants of a unique common ancestor. Conversely, the term monophyly , or monophyletic , builds on the Ancient Greek prefix μόνος ( mónos ), meaning "alone, only, unique", and refers to
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