﻿EXPERIMENTS IN MALARIAL TRANSMISSION. OZ6 



points of union with the anterior lobes. The four lateral lobes close before the 

 median, which fits against the otbers, effectually locking itself by means of the 

 tubercle and socket and precluding the entrance of water. The entire structure 

 is reenforced with strips of chitin running through various parts as shown by 

 the darker lines in the figure. On each side of the siphonette is a lateral comb 

 (PI. I, fig. 6, and PL II, fig. G) composed of fifteen teeth, those ventrad being 

 longest and all pointed directly caudad. The comb is surrounded ventrad, 

 anteriad and dorsad by a black, chitinous brace, from the dorsal cusp of which 

 projects a quadrifid seta (PI. I, fig. 7) four times the length of the comb teeth. 



Pupa (PI. IV, fig. 1). — The color of the pupa is dull gray, with a slightly 

 greenish tinge. The last abdominal segment is light ocher. The first abdominal 

 segment is darker dorsally than any succeeding one. The respiratory siphon is 

 dark gray externally, the inner surface being pearly-white and striate. The 

 eye-spots of the adult mosquito are plainly visible as dark areas on the 

 antero-lateral region of the pupal cephalo-thorax. 



The chwtotaxy of the pupa is as follows, the hairs and bristles of but one 

 side being given as in the larva: Submediad on the anterior margin of the 

 metathorax is 1 small, simple erect hair, on the scutello-abdominal suture of 

 the first abdominal segment, submediad, is a short, erect, bifurcate bristle, 

 followed laterad by 2 simple bristles, the second of which is 3 times as far from 

 it as the first; submediad on the middle of the second abdominal segment is a 

 palmate tuft of hairs composed of about 30 simple and bifurcate branches; 

 submediad on the third segment at its middle is a quadrifurcate bristle, followed 

 laterad by a simple, stout, curved bristle; on the fourth segment is a long, 

 trifurcate bristle, submediad on the posterior margins of the tergite, followed 

 laterad by two other simple bristles, the first of which is anterior to the margin, 

 the second on the margin ; on the fifth segment there is a bifurcate, submedian 

 bristle, followed laterad by a trifurcate bristle and antero-laterad by a bifurcate, 

 smaller one; the sixth segment has a simple, submedian bristle, longer than the 

 segment, on the posterior margin of the tergite, followed laterad by a quadrifur- 

 cate bristle, the seventh and eighth have bristles arranged similarly to those 

 on the sixth except that on the seventh there is a very small hair, mediad of 

 the long bristle, and its lateral bristle is bifurcate; on the eighth segment there 

 is a trifurcate bristle anteriad of the long, simple bristle; the ninth segment 

 bears a stout, dark brown, slightly curved bristle at the posterior lateral angle 

 and a single, submedian, dorsal hair at the posterior margin. 



Ventrally the fifth and sixth segments have a stout, latero-ventral bristle at 

 their posterior margins, while on the seventh and eighth there is a submedian 

 bristle on the posterior margin. 



The caudal fins, or pinnura (PL IV, figs. 4, 5), have the central and external 

 marginal veins brown at their bases, while the prolongation of the central 

 veins, the urachaeta?, are long, slender and recurved at their apices, forming a 

 hook (PL IV, fig. 5). The external margins of the pinnura are fringed with 

 delicate hairs from the uraeha'ta? to the apex of the external veins. 



Length of pupal period. — The pupal stage lasts from two and one-half to three 

 days according to weather conditions. 



Habits of pupa?. — The pupa?, as a rule, remain at the surface in full sunshine, 

 but swim very rapidly to the bottom or among or beneath the layers of alga; when 

 any object comes near. They can remain submerged for from fifteen to forty- 

 five seconds, but usually return to the surface almost immediately. Their pale 

 gray color makes them very difficult to detect, and were they to remain quiet at 

 the surface they would be well protected by the background of green or light 

 gray of the decaying, matted algae. No special or notworthy difference appears to 

 exist between their position and that of the pupa? of Culex microanmilatus Theob., 



