_Phlebotomus vexator_, Coq.: Yellow, the mesonotum brown, hairs chiefly brown; legs in certain lights appear brown, but are covered with a white tomentum; wings hyaline, unmarked; the first vein (R_1) terminates opposite one-fifth of the length of the first submarginal cell (cell R_2); this cell is slightly over twice as long as its petiole; terminal, horny portion of male claspers slender, bearing many long hairs; the apex terminated by two curved spines which are more than one-half as long as the preceding part, and just in front of these are two similar spines, while near the middle of the length of this portion is a fifth spine similar to the others. Length 1.5 mm. The life-history of the Phlebotomus flies has been best worked out for the European _Phlebotomus papatasii_ and we shall briefly summarize the account of Dœrr and Russ (1913) based primarily on work on this species. The European Phlebotomus flies appear at the beginning of the warm season, a few weeks after the cessation of the heavy rains and storms of springtime. They gradually become more abundant until they reach their first maximum, which in Italy is near the end of July (Grassi). They then become scarcer but reach a second maximum in September. At the beginning of winter they vanish completely, hibernating individuals not being found. After fertilization there is a period of eight to ten days before oviposition. The eggs are then deposited, the majority in a single mass covered by a slimy secretion from the sebaceous glands. The larvæ emerge in fourteen to twenty days. There is uncertainty as to the length of larval life, specimens kept in captivity remaining fifty or more days without transforming. Growth may be much more rapid in nature. The larvæ do not live in fluid media but in moist detritus in dark places. Marett believes that they live chiefly on the excrement of pill-bugs (Oniscidæ) and lizards. Pupation always occurs during the night. The remnants of the larval skin remain attached to the last two segments of the quiescent pupa and serve to attach it to the stone on which it lives. The pupal stage lasts eleven to sixteen days, the adult escaping at night. Only the females suck blood. They attack not only man but all warm-blooded animals and, according to recent workers, also cold-blooded forms, such as frogs, lizards, and larvæ. Indeed, Townsend (1914) believes that there is an intimate relation between _Phlebotomus_ and lizards, or other reptiles the world over. The Phlebotomus passes the daylight hours within the darkened recesses of the loose stone walls and piles of rock in order to escape wind and strong light. Lizards inhabit the same places, and the flies, always ready to suck blood in the absence of light and wind, have been found more prone to suck reptilian than mammalian blood.