Phthiraptera

Order

PHTHIRAPTERA
(Greek, phthir = lice; aptera = wingless)

Suborders

Amblycera, Ischnocera, Anoplura and Rhynchopthirina

Description

Lice are obligate ectoparasites (unable to live anywhere else except on the skin of another organism). They are found on all bird species and almost all mammals except bats. All species of lice are wingless, the eyes are either absent or reduced and the antennae are either greatly reduced (composed of short, straight lengths - filiform) or are modified to form "claspers" to aid in holding onto the host. The bodies of all species are more or less flattened from top to bottom (dorsoventrally) and the legs are always modified for grasping the host. Legs are usually curled and possess hooks or spines. Depending upon the food requirements of the individual species of louse, the mouthparts may have well developed mandibles or may be modified for piercing and sucking.

Life Cycle

The eggs (nits) are laid directly onto the fur, feathers or skin of the host. The emerging juvenile resembles a smaller version of the adult (nymph) except that it is less pigmented.

Distribution

Cosmopolitan

Members

Lice.

Food

Depending on mouthpart structure, lice exploit various parts of the host. The jawed species feed on fragments of skin, hair or feathers while species with piercing-sucking mouthparts feed on blood.

Importance

Lice are extremely important ectoparasites of various domesticated animals and are also important parasites of humans. Severe infestations of lice in poultry can destroy the feathers of the birds and leave large bare patches. While the lice do not directly kill the birds, they annoy them so much with the constant irritation that the the bird progressively weakens and dies. Control of sheep lice is costly and necessary to prevent considerable losses of animal condition and fleece. The piercing-sucking lice are able to spread disease through their invasion of the blood system of the organism. The human inhabiting species Pediculus humanus, Pediculus capitis and Pthirus pubis carry a considerable range of diseases. Typhus, relapsing fever and trench fever are three diseases carried by human lice. Interestingly, the disease typhus appears to be spread by crushing the bodies of the lice through scratching. The inoculation of the crushed bodies of lice (or their faecal deposits) onto fresh abrasions is caused by finger nails rather than direct blood transfer.