MOSQUITOES (CULICID^), §S 



Species that frequent houses breed in butts or tubs of rain-water or 

 in other vessels of water within or in the precincts of the houses 

 themselves, or in cesspools and wells which are open to the air. In 

 the case of the best-known species of Culex that infest houses, the 

 eggs are laid on the surface of the water in the so-called " boat- 

 shaped" masses; Anopheles eggs, on the other hand, are laid 

 separately, and float together into roughly star-shaped groups or in 

 lines; in Mansonia and Stegomyia they are also laid separately. The 

 eggs of the different genera vary much in form. 



The mosquito larva is usually a small greenish, greenish-brown, or 

 brown creature, occasionally red and blue, with a round head, a 

 rounded swollen thorax, and an elongated jointed abdomen, from 

 neai' the end of which, in Ctdex, ^Edes, Megarhina, Stegomyia, Man- 

 sonia, and Mucidus, the bi-eathing-tube arises. Jn the pupa the 

 head and thorax are fused into a mass, on the sides and front of which 

 depend the rudiments of the wings, leg«, and proboscis, while from 

 the dorsal side project a pair of funnel-shaped breathing- organs ; the 

 terminal segment of the abdomen bears a pair of swimming-plates. 

 In the case of Culex the larvse and pupae are exceedingly active, 

 moving about in the water by a jerking or wriggling motion of the 

 body ; they are under the necessity of coming to the surface to 

 breathe at frequent intervals. The larva of Ayiopheles, which 

 is devoid of a prominent air- tube, is more sluggish, and its habit 

 is to float horizontally at the surface of the water. 



In the case of Culex fatigans, Wied., it was found by Howard 

 that the minimum time occupied by the whole life-history cycle 

 was ten days — " namely, sixteen to twenty-four hours for the 

 ("^g, seven days for the larva, and two days for the pupa." 

 But the period necessary for a generation " is almost infinitely 

 enlarged if the weather be cool," so that it is also permissible to 

 suppose that it is accelerated by heat. 



In the perfect state the male insects die quickly in conGnement, 

 but the females are longer-lived. Dr. Bancroft has kept Culex 

 tigripes alive for seventy days in continement. In cold climates 

 large numbers of the perfect insects pass the winter in a state 

 of hibernation, but a few species, such as Anopheles hifurcatus, do 

 so as larva?. 



