. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. 82 Parasitic Arthropods Three species commonly attack man. Strangely enough, there are very few accurate data regarding their life history. Pediculus humanus (fig. 65), the head louse, is the most widely distributed. It is usually referred to in medical literature as Pedi- culus capitis, but the Linnean specific name has priority. In color it is of a pale gray, blackish on the margins. It is claimed by some authors that the color varies according to the color of the skin of the host. The abdom
. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. 82 Parasitic Arthropods Three species commonly attack man. Strangely enough, there are very few accurate data regarding their life history. Pediculus humanus (fig. 65), the head louse, is the most widely distributed. It is usually referred to in medical literature as Pedi- culus capitis, but the Linnean specific name has priority. In color it is of a pale gray, blackish on the margins. It is claimed by some authors that the color varies according to the color of the skin of the host. The abdomen is composed of seven dis- tinct segments, bearing spiracles laterally. There is considerable variation in size. The males average mm. and the females mm. in length. The eggs, fifty to sixty in number, stick firmly to the hairs of the host and are known as nits. They are large and conspicuous, especi- ally on dark hair and are provided with an operculum, or cap, at the free end, where the nymphs emerge. They hatch in about six days and about the eigh- teenth day the yoting lice are sexually mature. The head lice live by preference on the scalp of their host but occasionally they are found on the eyelashes and beard, or in the pubic region. They may also occur elsewhere on the body The penetration of the rostrum into the skin and the discharge of an irritat- ing saliva produce a severe itching, accompanied by the formation of an eczema-like eruption (fig. 66). When the infestation is severe, the discharge from the pustules mats down the hair, and scabs are formed, tmder which the insects swarm. " If allowed to run, a regular carapace may form, called trichoma, and the head exudes a foetid. Pediculosis of the head. The illustration shows the characteristic indications of the presence of lice, viz: the occipital eczema gluing the hairs together, the swollen cervical glands, and the porrigo, or erup- tion of contagious pustules upon the neck. After Please note
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