Pediculus corporis (= P. vestimenti) the body louse, is larger than the preceding species, the female measuring 3.3 mm., and the male 3 mm. in length. The color is a dirty white, or grayish. P. corporis has been regarded by some authorities as merely a variety of P. humanus but Piaget maintains there are good characters separating the two species.
The body louse lives in the folds and seams of the clothing of its host, passing to the skin only when it wishes to feed. Brumpt states that he has found enormous numbers of them in the collars of glass-ware or grains worn by certain naked tribes in Africa.
Exact data regarding the life-history of this species have been supplied, in part, by the work of Warburton (1910), cited by Nuttall. He found that Pediculus corporis lives longer than P. humanus under adverse conditions. This is doubtless due to its living habitually on the clothing, whereas humanus lives upon the head, where it has more frequent opportunities of feeding. He reared a single female upon his own person, keeping the louse enclosed in a cotton-plugged tube with a particle of cloth to which it could cling. The tube was kept next to his body, thus simulating the natural conditions of warmth and moisture under which the lice thrive. The specimen was fed twice daily, while it clung to the cloth upon which it rested. Under these conditions she lived for one month. Copulation commenced five days after the female had hatched and was repeated a number of times, sexual union lasting for hours. The female laid one hundred and twenty-four eggs within twenty-five days.
The eggs hatched after eight days, under favorable conditions, such as those under which the female was kept. They did not hatch in the cold. Eggs kept near the person during the day and hung in clothing by the bedside at night, during the winter, in a cold room, did not hatch until the thirty-fifth day. When the nymphs emerge from the eggs, they feed at once, if given a chance to do so. They are prone to scatter about the person and abandon the fragment of cloth to which the adult clings.
The adult stage is reached on the eleventh day, after three molts, about four days apart. Adults enter into copulation about the fifth day and as the eggs require eight days for development, the total cycle, under favorable conditions, is about twenty-four days. Warburton's data differ considerably from those commonly quoted and serve to emphasize the necessity for detailed studies of some of the commonest of parasitic insects.
Body lice are voracious feeders, producing by their bites and the irritating saliva which they inject, rosy elevations and papules which become covered with a brownish crust. The intense itching provokes scratching, and characteristic white scars ([fig. 67]) surrounded by brownish pigment ([fig. 68]) are formed. The skin may become thickened and take on a bronze tinge. This melanoderma is especially marked in the region between the shoulders but it may become generalized, a prominent characteristic of "vagabond's disease." According to Dubre and Beille, this melanoderma is due to a toxic substance secreted by the lice, which indirectly provokes the formation of pigment.
Control measures, in the case of the body louse, consist in boiling or steaming the clothes or in some cases, sterilizing by dry heat. The dermatitis may be relieved by the use of zinc-oxide ointment, to which Pusey recommends that there be added, on account of their parasiticidal properties, sulphur and balsam of Peru, equal parts, 15 to 30 grains to the ounce.