49° 



Malaria 



1. Proboscis curved in the female Psorophora. 



2. Proboscis straight in the female: 



A. Palpi with three segments in the female. 



a. Third segment somewhat longer than 



the first two Culex. 



b. The three segments are equal in 



length Stegomyia. 



B. Palpi with four segments in the female. 



a. Palpi shorter than the third of the 



proboscis. Spotted wings. Theobaldia. 



b. Palpi longer than the third of the 



proboscis. Irregular scales on the 

 ■ wings Mansonia. 



C. Palpi with fine segments in the female. . . . Taniorrhynchus, 

 II. Posterior cross- vein in line with the mid-cross-vein. . . Joblotina. 



III. Posterior cross-vein further from the base of the wing 



than the mid-cross-vein Mucidus. 



Male mosquitoes can at once be recognized by the pennate 

 antennae which appear like plumes on each side of the head. They 

 commonly "swarm" in flocks, do not suck blood, and are not com- 

 monly found in or about human habitations. Comparatively little 

 is known of their habits. Cohabitation of the sexes occurs but once 

 after which the males commonly die. The females after fecunda- 

 tion require a meal of blood before they become gravid and ready to 

 oviposit. Oviposition takes place in water. During the winter 

 many gravid females hibernate in cellars in a very inactive condi- 

 tion, but are immediately ready to fly to appropriate places and lay 

 their eggs with the return of warm weather. In hot climates some 

 of them estivate — i.e., become similarly inactive during the dry 

 period, but are ready to fly to the water and oviposit as soon as the 

 rains begin again. The breeding places vary with the species. 

 Fresh water is the usual preference, but a few select pools of brack- 

 ish water, and one or two species prefer salt water. Most of the 

 malaria-bearing species of anopheles prefer pools of fresh clear 

 water, some prefer running water in small streams with a slow cur- 

 rent. A few breed in large rivers. Some species are notably domes- 

 tic and oviposite in wells, cisterns, .water-butts, cans and any other 

 available collection of water. . 



The eggs are laid as the female hovers upon the surface, touching 

 the water from time to time, with the tip of the abdomen, each 

 time depositing an egg. Culex eggs are fastened together side by 

 side to form a kind of minute raft, but anopheles eggs are laid singly 

 and float away independently of one another. If at the time the 

 waters are receding, the eggs catch upon the leaves and stems of 

 plants they may remain alive until the waters rise again before 

 hatching. Dry eggs are sometimes able to remain alive for long 

 periods, and may even be frozen without being killed. Cazeneuve 

 hatched eight larvffi from eggs obtained by thawing a block of 

 ice taken from a swamp in North China, where the temperature 

 had gone as low as — 32°C. When' conditions are favorable the 

 eggs hatch in two or three weeks. The anopheles larvae feed at 



