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306 were made, hence one of the names for the disease, papatasii fever) lays about forty eggs, selecting for the purpose damp localities such as the walls of cellars, of latrines, cesspools, crevices in walls, caves and embankments. The cycle of egg, larva and imago takes about one month in warm and upwards of two months in cooler weather to complete. The duration of the life of the imago is not known. It is difficult to keep it in captivity; under such conditions it rarely lives as long as fifteen days.

Fig. 63.—a, Abdomen of female phlebotomus, showing eggs; b, young phlebotomus. (After Alcock.)

There has been much confusion in the nomenclature of the various species of phlebotomus, and it has not been determined which of them, other than P. papatasii, convey the infection.

Pathology.—Yellow fever, dengue and phlebotomus fever have several important points in common, a circumstance suggestive of the possibility of a common or, at all events, a similar origin. Each is transmitted by an insect; their germs occur in the blood-stream and are ultramicroscopic; they are