SPOROZOA 1121 



under a hand lens, are two pairs of organs; next to the proboscis 

 are the palpi, and outside of these the antennae ; the latter serve 

 to distinguish the sexes, the antennae of the male being heavily 

 ornamented with a bushy, hairy investment (plumose) ; the female 

 antennae, on the contrary, are provided with relatively few, short 

 hairs, arranged in rings at the joints (pilose). In the anophelines 

 the palpi in both sexes are long, at least as long as the probocis, 

 while in all other mosquitoes they are short in the female or in 

 both sexes. This is the principal differential point. The wing mark- 

 ings are of some help, since anopheline wings are almost always 

 spotted. Quite characteristic also is the position assumed by both 

 genera while at rest; among the anophelines the head, thorax and 

 abdomen are all in a straight line and the insect makes an angle 

 with the surface upon which it rests; while the culicidae are hump- 

 backed, the thorax and head are bent on the abdomen so that the 

 latter lies parallel to the surface. By these characteristics it is 

 easy to identify a mosquito as an anopheline, but the further classifi- 

 cation into species is less simple, and works on entomology must 

 be consulted. 



The life history of the anophelines is not yet completely known ; 

 they fly and bite at dusk and dawn and during the night, and thus 

 differ from stegomyia and most other culicidae, which are day-time 

 biters. Their breeding places have already been described ; of special 

 importance are the temporary collections of water in which the 

 larvae, unhampered by their natural enemies, quickly reach maturity 

 in large numbers. With abundance of food and warm weather, the 

 larva? may require 110 more than ten days to complete their three 

 molts. The female alone sucks blood, the male living on fruit and 

 vegetable juices. Egg-laying does not take place until after a meal 

 of blood, and it is possible that the female journeys fairly long 

 distances to obtain this food, and that the first flight, from breeding 

 place to human habitations, may be longer than subsequent flights. 

 In general the flight is short, not over three hundred yards, and 

 Gorgas found, in Panama, that a clearing of that width about houses 

 gave ample protection. 



The incubation period of the parasite in the mosquito is about 

 twelve days, after which the insect remains a carrier during the 

 rest of its life, and as the health of the mosquito is unaffected, this 

 may be for two months or more. 



