VII] HIBERNATION AND LONGEVITY 71 



characteristic appearance and seems to be standing on its head. 

 On the other hand, in the Culicinae the proboscis forms an angle 

 with the rest of the body and therefore the insect has a hump- 

 backed appearance ; moreover, it generally rests with its body 

 parallel to the surface, or with the posterior extremity bent 

 towards the surface. These differences in the position of rest, 

 whilst being useful for the recognition of living mosquitoes, 

 are by no means constant, as Anopheles sometimes settles in 

 the same manner as Cule%. The differences between the two 

 positions are well shewn in Fig. 30. 



Hibernation. In cold regions mosquitoes generally pass 

 through the winter in the egg stage, but in addition some 

 of the females hibernate in dark corners. During last 

 winter several females of A. maculipennis and Theobaldia 

 annulata hibernated at the top of a wardrobe in the author's 

 bedroom at Grantchester, disappearing after the warm weather 

 in April. In tropical countries mosquitoes generally hibernate 

 during the dry season, when all the breeding pools disappear. 

 In addition, however, some of their eggs may remain in 

 the mud at the bottom of dried pools and develop when these 

 are again filled with water. 



Longevity. There are very few observations on the longevity 

 of mosquitoes, but the length of life of the female seems to be far 

 greater than that of the male. Those females which hibernate 

 may live for nearly a year, but in confinement Anophelines have 

 not been kept alive for more than about a month. In the case 

 of Aedes Knab has found that the female may live for at least 

 three months, and Stegomyia has been kept alive for 154 days. 



Mating habits. In many species, e.g. Culex pipiens, the 

 males form large swarms, to which the females seem to be 

 attracted. The latter, however, merely fly to the swarm in 

 order to secure a mate, and as soon as this is effected the pair 

 at once drops out of the swarm. This habit of forming swarms 

 is not entirely confined to the male sex, for swarms of females 

 have been observed side by side with those of males. 

 Copulation may be accomplished either on the wing, as in the 

 case of Stegomyia fasciata, or whilst resting, and is generally 

 of but short duration. 



