Higher Taxon Psocoptera

Psocoptera

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Higher Taxon Psocoptera

Booklice, Psocids

Compiler and date details

2007 - updated, ABRS

1996 - C.N. Smithers, Australian Museum, Sydney, New South Wales, Australia

Introduction

The Psocoptera are small (1–10 mm) exopterygote Neoptera, commonly referred to as psocids, booklice (domestic species) or barklice. They have a characteristic appearance because of their rounded head which has a bulbous postclypeus, their long antennae, enlarged pterothorax and the way in which most species hold their wings with the posterior margins meeting along the dorsal midline of the body and with the lamina of the wings sloping downwards at an angle to the abdomen. Alary polymorphism, brachyptery or aptery in one or both sexes is fairly common. This results in some adults being superficially very similar to nymphs.

About 3500 species of psocids have been described, of which fewer than 300 are recorded from Australia. Existing collections contain many undescribed Australian species and there is no doubt that many more remain to be collected. General accounts of the order, which provide morphological, biological and ecological as well as taxonomic information, include those of Badonnel (1951), Weidner (1972), Smithers (1972—which includes definitions and illustrations of the diagnostic features of the families and genera recognised at the time), Günther (1974), New (1974) and Smithers (1982, 1991). The most recent world species list, now somewhat out-dated but still useful as a starting point, is that of Smithers (1967). Mockford (1987) has provided a very useful account of the nymphs which, although based on North American forms, is largely applicable to Australian families. The bibliography of Smithers & Lienhard (1992) gives entry to world literature, and Smithers (1990) provides keys and illustrations to families and genera.

Classification
A brief history of the classification of the Psocoptera is given by Smithers (1972). Pearman (1936) outlined a classification using a wider range of characters than those used previously. He recognised a large number of families which were not defined in detail but for each of which one or two typical genera were mentioned. Unfortunately, the more detailed treatment which was mentioned at the time never materialised. Pearman's work, and that of Roesler (1944), is, nevertheless, the platform on which Badonnel (1951) erected his classification and this, with subsequent modification by various authors, forms the basis of the arrangement now in general use. The families are mostly placed in informal groups, not necessarily equivalent in concept to the superfamilies of other orders, except for the Asiopsocoidea and Caecilioidea of Mockford & Garcia Aldrete (1976) which replace Pearman's family group Caecilietae. It is preferable to retain the other general groups for practical purposes until further study provides elucidation of relationships of the families. A first attempt to do this on a broad scale (Smithers 1972) has been published but, as indicated at the time, it is preferable to work with the present arrangement for practical purposes until the phylogeny suggested there has been tested more widely by further work. A conspectus of the families is given to indicate the current arrangement. They are dealt with serially in the same order in Smithers (1996) and here, with genera listed alphabetically in the families without reference to their subfamilies. Characters of the suborders, family groups and families are given by Smithers (1972).

Biology
Psocoptera are found in a wide variety of terrestrial habitats. These include living and dead foliage, on or under bark of trunks, branches and twigs, in litter, on fences and walls, on or under rocks, in caves, in human habitations and in stored products. They have been found in ants' nests, bee hives and in birds' nests. The nymphs of one exceptional Australian species make short tunnels in wood. Psocids feed mainly on microflora and organic debris. Some species occur in several types of habitat and have a wide food range but others, with more specialised habitat requirements, have restricted diets. Some of these feed solely on unicellular algae, lichens or on fungi associated with a specific substratum, such as dead leaves. Some species can be reared on yeast media. There is often some general correlation between food sources, habitats, morphology and systematic position.

Most Psocoptera are solitary, aggregations occurring where food is abundant or where other factors influence behaviour. Various degrees of intraspecific association are also found. In some species individuals are found in loose groups of adults and nymphs. A few occur in close physical contact as nymphs, but disperse when adult. Some live under larger or smaller communal webs; in extreme cases the webs cover whole tree trunks and branches (Archipsocus Hagen). Parthenogenesis is fairly common and viviparity is known in some Archipsocidae. Many use silk and an encrustation of anally voided bark to cover their eggs.

Little is known of the detailed biology and ecology of native Australian species. As grazers on the microflora they sometimes occur in enormous numbers and are clearly important in making available to other parts of the food web resources derived from the microflora. Psocids are a wide variety of predators, including spiders, pseudoscorpions, neuropteran larvae, ants, reduviids, wasps, thrips and birds. They are attacked by parasitic nematodes and entomophagous fungi. Mymarid parasites and mirid bugs destroy their eggs and braconids attack nymphs and adults.

Psocoptera are becoming increasingly recognised as important pests of stored products, especially farinaceous foods. They are a nuisance in houses and are known to be responsible for some allergic reactions in people working with infested material such as fabricated building materials and stock feed. They may also be important in transmission of some parasitic worms of sheep.

A general account of the biology of Psocoptera is given by New (1987).

Zoogeography
All families found in Australia are also found elsewhere. As a group, Psocoptera appear to be highly vagile and frequently enter new areas. Many species, especially those associated with stored products (e.g. Liposcelis Motschulsky species), are easily carried long distances by commerce. Quarantine interceptions frequently include such species but, surprisingly, some of the more widespread of these have not yet been recorded from Australia. In addition to the cosmopolitan domestic element, there is a typically Gondwanan element (e.g. Sphaeropsocopsis Badonnel) as well as some tropical species which have their relatives to the north of Australia (e.g. Calopsocus Hagen and Mouldsia Smithers). The tropical areas of Australia also have species which belong to groups with mainly pan-tropical distributions (e.g. Archipsocus and Hemipsocus Sélys-Longchamps). An important part of the fauna belongs to groups which are widespread beyond Australia but which have evolved many endemic taxa here (e.g. Psocidae). Thornton (1985) discusses the distribution and ecology of arboreal species and Smithers & Thornton (1982, 1990) discuss the zoogeography of Melanesian species.

Relationships
The nearest living relatives of the Psocoptera appear to be the putative hemipteroid order Phthiraptera. Mockford (1993) gives sound reasons for doubting that Permian fossils referred to the Psocoptera are correctly assigned and suggests that the earliest unquestionable psocid fossils are to be found in the Cretaceous.

Acknowledgements

I would like to thank my wife for her constant help in my work on the Psocoptera, the librarians of the Australian Museum whose help has made access to hard-to-find literature possible, and the staff of the Australian Museum Entomology Department for giving me continuing access to the collections. I am grateful for the help and kindly criticism of many colleagues, especially those working on the Psocoptera, Dr Shane McEvey for his efforts to make me 'computer literate', the Australian Biological Resources Study for financial support and its staff for help and advice during the preparation of this catalogue.

Database Notes

The Psocoptera section of the Catalogue (Smithers 1996) is based on information coming to my notice prior to the 30th June, 1994. In the introduction to each family the numbers of genera and species recorded for Australia are given with approximate numbers for the world fauna. In almost every family there are some exceptional species which do not agree in all points with the characters given for the family.

The information on the Australian Faunal Directory site for the Psocoptera derived from the Zoological Catalogue of Australia database, has been updated by ABRS to include new taxa from Schmidt & New (2004), and species recognised in the fauna of Christmas Island by Smithers (1995).

Limital Area

Distribution data in the Directory is by political and geographic region descriptors and serves as a guide to the distribution of a taxon. For details of a taxon's distribution, the reader should consult the cited references (if any) at genus and species levels.

Australia is defined as including Lord Howe Is., Norfolk Is., Cocos (Keeling) Ils, Christmas Is., Ashmore and Cartier Ils, Macquarie Is., Australian Antarctic Territory, Heard and McDonald Ils, and the waters associated with these land areas of Australian political responsibility. Political areas include the adjacent waters.

Terrestrial geographical terms are based on the drainage systems of continental Australia, while marine terms are self explanatory except as follows: the boundary between the coastal and oceanic zones is the 200 m contour; the Arafura Sea extends from Cape York to 124 DEG E; and the boundary between the Tasman and Coral Seas is considered to be the latitude of Fraser Island, also regarded as the southern terminus of the Great Barrier Reef.

Distribution records, if any, outside of these areas are listed as extralimital. The distribution descriptors for each species are collated to genus level. Users are advised that extralimital distribution for some taxa may not be complete.