Family PHILOPTERIDAE

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Family PHILOPTERIDAE

Compiler and date details

R.L. Palma Museum of New Zealand, Wellington, New Zealand

Introduction

The Philopteridae Burmeister, 1838 are the largest and morphologically most diverse family of lice with about 1500 known species parasitic on members of all orders and most families of birds. In Australia, about 300 species and subspecies are recorded in this family, and it is expected that many more will be found. With the exception of one species found on Madagascan mammals, which some authors place separately in the family Trichophilopteridae (Emerson & Price 1985; Lyal 1985), philopterid lice are found exclusively on birds.

Philopterid lice are distinguished from the other families of Ischnocera by a combination of morphological characters. They can be separated from the mammal-infesting Trichodectidae by the presence of two claws on each leg and five segments in the antennae, and they differ from the Heptapsogasteridae by having eight visible abdominal segments, not seven.

Philopterid bird lice feed exclusively on feathers and are very well adapted to cling and crawl over feather barbs. A considerable amount of parallel and convergent evolution has taken place among these lice which live on a great variety of hosts bearing feathers of diverse structure. The result is a wide range of morphological types each specific to a particular site on the host, and in many cases superficially similar on different hosts groups. These morphotypes grade into each other to the extent that original relationships have been obscured and are therefore difficult to detect (Clay 1951a, 1951b).

Consequently, the subdivision of the Philopteridae into natural groups has proven to be a difficult task with no general agreement among phthirapterists. Some authors have subdivided it into many subfamilies or even divided it into several families (e.g. Eichler 1963). The number of philopterid genera recognised as valid is also a matter of contention. Most modern authors have followed the more conservative generic classification established by Hopkins & Clay (1952), but some have taken the view that almost any slightly different species-group deserves generic recognition. Thus, the latter view has produced systems which are both unnatural and unmanageable (e.g. Eichler 1982; Tendeiro 1975; Zlotorzycka 1967).

The most important features used for the identification of philopterid genera are found both in and on the head. Clay (1951a) established the basis for the understanding of head structures and their terminology, and that should be used for the accurate description and recognition of valid genera within this family. No key is available to all genera of Philopteridae. The most comprehensive is that published by Ledger (1980) which only includes the genera of lice found in Africa, south of the Sahara. Notwithstanding its restricted geographical coverage, Ledger's key is suitable for the identification of over 50 of the genera occurring in Australia.

Generally, all the species of a philopterid genus are distributed within a single order of birds (e.g. Pectinopygus on Pelecaniformes), sometimes within a single family (e.g. Naubates on Procellariidae), and in fewer cases in a group of genera (e.g. Pseudonirmus on Daption, Thalassoica and Pagodroma), in one genus (e.g. Episbates on Diomedea) or even on a single species (e.g. Bedfordiella on Lugensa brevirostris). There are a few exceptions like the genera Brueelia, Rallicola and Saemundssonia, represented by many species which are widespread over two or more orders of birds (Clay 1957).

Both the great morphological diversity and the high level of host specificity achieved by philopterid lice are useful tools for the elucidation of host relationships and the identification of closely related host taxa which are otherwise poorly defined (e.g. Imber 1985; Melville 1985).