. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. 74 Parasitic Arthropods there develop after about seven days, the hexapod larvae. These molt on the sixteenth day to form an octopod nymph, which molts again the twenty-first day. At the end of the fourth week the nymphs molt to form the sexually mature males and the so-called pubescent females. These pair, the males die, females again cast their skin, and become the oviparous females. Thus the life cycle is completed in about twenty-eight days. The external temperature exercises a gre
. Handbook of medical entomology. Insect pests; Insects as carriers of disease; Medical parasitology. 74 Parasitic Arthropods there develop after about seven days, the hexapod larvae. These molt on the sixteenth day to form an octopod nymph, which molts again the twenty-first day. At the end of the fourth week the nymphs molt to form the sexually mature males and the so-called pubescent females. These pair, the males die, females again cast their skin, and become the oviparous females. Thus the life cycle is completed in about twenty-eight days. The external temperature exercises a great influence on the develop- ment of the mites and thus, during the winter, the areas of infesta- tion not only do not spread, but they become restricted. As soon as the temperature rises, the mites increase and the infestation becomes, much more 57. Sarcoptes scabiei. Diagrammatic representation of the course in the skin of man. In considering the possible sources of infestation, and the chances of reinfestation after treatment, the question of the ability of the mite to live apart from its host is a very important one. Unfortunately, there are few reliable data on this subject. Gerlach found that, exposed in the dry, warm air of a room they became very inactive within twenty-four hours, that after two days they showed only slight movement, and that after three or four days they could not be revived by moisture and warming. The important fact was brought out that in moist air, in folded soiled underwear, they sur- vived as long as ten days. Bourguignon found that under the most favorable conditions the mites of Sarcoptes scabiei equi wotild live for sixteen days. The disease designated the "itch" or "scabies," in man has been known from time immemorial, but until within less than a hundred years it was almost universally attributed to malnutrition, errors of. Please note that these images are extracted from scanned page images that may have been
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