Key to Australian Freshwater and Terrestrial Invertebrates
Phylum Arthropoda
Subphylum Hexapoda
Class Insecta
Order Phthiraptera
Common name: lice
Overview
Phthiraptera, or lice, are tiny, wingless, flat-bodied insects that are external parasites (ectoparasites) of birds and mammals, including humans. Typically, they are restricted to one or only a few hosts and spend their entire life clinging to hair or feathers. Lice have very short antennae, small or no eyes, hook-like claws and range from 0.5�11 mm in length. They usually favour a specific part of the host's body and have a variety of morphological adaptations, especially those which assist them in holding onto the host, such as a flattened body, strong legs or claws, powerful mandibles and numerous setae. Sucking lice have mouthparts in the form of a pointed tube (proboscis) for piercing and sucking, whereas as biting lice have chewing, mandibulate mouthparts. Lice are rarely seen without the aid of magnification and are short-lived
Distribution and diversity
Almost all birds and mammals carry lice, and they are found throughout Australia wherever their hosts occur. Worldwide there are more than 3,000 known species of lice and many more remain undescribed. For the Australian fauna, 465 species are recorded in 115 genera from 14 families; about 80% of these parasitise birds. However, this group of insects has not been collected from a large number of potential Australian hosts and as many as 200 more species await discovery.
Life cycle
Lice complete their entire life cycle on their host. Typically males are much rarer than females; mating occurs frequently and sperm transfer is direct. Parthenogenesis also occurs in some species. The female can lay up to nine eggs per day on the hair or feathers where they are cemented in species-specific sites to limit dislodgement by host grooming. The nymphs resemble adults and develop through three instars before they reach maturity. Depending on the species, lice are relatively short lived, usually from 2�8 weeks.
Feeding
Most sucking lice feed on the blood of the animals on which they live, while biting lice usually feed on the feathers, fur, skin detritus or mucus of their host. Both adults and nymphs have a similar diet.
Ecology
Lice are obligate parasites and their ecology and behaviour are intimately linked to those of the host. Some species are restricted to just one host species and will often spend their entire life on a specific part of the body. Transmission is largely opportunistic, occurring when hosts are in close contact with each other, such as during breeding or care of offspring. Lice have an impact on host health and fitness, either as a result of their feeding or by acting as vectors of organisms that cause disease. Hosts have evolved diverse behavioural (e.g. grooming, rolling in dirt or ants � 'anting'), morphological (e.g. bill shape) and physiological (e.g. natural resistance) adaptations to control their lice. Lice are of considerable veterinary importance, since all species of domestic birds and mammals in Australia are hosts to one or more species of lice. They are responsible for loss of livestock production in the meat, wool, leather, dairy and poultry industries. The rabbit myxomatosis virus introduced for the biological control of rabbits in Australia can be transmitted by the rabbit louse (Haemodipsus venticosus). A few species of lice have adapted to live and feed on humans, e.g. the head louse, Pediculus capitis, the eggs of which are commonly called nits, and the body louse, Pediculus humanus. Human lice feed on blood and therefore can cause irritation and anaemia, but they are most damaging to human health as disease vectors.
