Pthiridae

There are two species in Phthirus in the world: a cosmopolitan species infesting humans, and the other, Phthirus gorillae, infesting the gorilla.

Pubic louse, crab louse, Phthirus pubis (Fig. I4.3a-d) Adults are 1.5-2 mm long. They are nearly as long as wide, and resemble a crab; the thorax is wide where it contacts with the abdomen. The first pair of legs is reduced and the claw is small; legs 2 and 3 are large and have a well-developed claw. The distance between two extended legs is approximately the distance apart of the coarse hairs on the parts of the body this louse infests. The abdomen has four pairs oflateral sclerotized tubercles. The first three pairs of abdominal spiracles are small and in a row; the remaining spiracles are large and located along the edge of the abdomen. Nymphs resemble adults. The third-stage male nymph is 1.3-1.4 mm long, and usually with two later tubercles. The third-stage female nymph is 1.01.5 mm long, and usually with four lateral tubercles. Adults and nymphs are found in the pubic region of the body, but they may occur in armpits, mustache, beard, and eyebrows. Eggs are yellowish white, about 1 mm long, and strongly attached to the hair or clothing. Several eggs may be attached to a single hair. Females lay about three eggs per day, and fecundity is 26-30 eggs. Hatching occurs in 6-8 days, and development takes 13-17 days at normal skin temperature. Adults live about 30 days, butaway from the host they may live only 1 day. Adults

Figure 14.3 Phthiraptera.(a) Phthirus pubis male (dorsal/ventral view); (b) P. pubis male, third-stage nymph (dorsal/ventral view); (c) P. pubis female (dorsal/ventral view); (d) P. pubis female, third-stage nymph (dorsal/ventral view).

(Serinus canarius); lice occur under the wings and on the back of the birds.

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