658 DOMESTIC ANIMALS, DAIRYING, ETC. 



members of the genus Culex. The egg-mass or raft is the product 

 of one female and, according to Theobald, is laid soon after sunri.se, 

 and also at dusk if the weather is warm and still. Examination 

 under a hand-lens shows a distinct structure to the mass, it being 

 made up of individual eggs, standing close together in an upright 

 position, the bottom of the egg being larger than the top, thus mak- 

 ing the raft boat-shaped. Each raft is estimated to contain from 

 two to three hundred eggs, the individual egg being hardly visible 

 to one unaccustomed to looking at objects so small. The lightness 

 of the mass insures its floating on the surface. Howard says that 

 if the eggs are kept completely immersed the larvae will never de- 

 velop, this being because of the inability of the developing em- 

 bryos to obtain the necessary air supply. The peculiar structure 

 of the bottom of the eggs prevents the water from actually wetting 

 them. 



When the eggs hatch they open downward letting the larvae 

 into the water. This occurs from twenty-four hours, under favor- 

 able conditions, to two or three days, after the eggs are deposited. 

 Naturally the young on hatching are very small but develop in a 

 few days into fair sized wrigglers. These are the common natural 

 history objects of the rain-water barrel which, as youngsters, we all 

 believed were rained down. 



The larva of this species is found normally at the surface of 

 the water with its head in a downward position. The explanation 

 of this peculiar position is this: the larvae of this and all species of 

 mosquitoes, though aquatic as regards living in and obtaining their 

 food from the water, are true air-breathers and must necessarily 

 come to the surface to obtain the air. The larva while breathing 

 at the surface continues to feed beneath; hence the position of the 

 head downward. It moves away when disturbed and can fre- 

 quently be seen foraging about in the water for food but coming 

 regularly to the surface to breathe. Its food consists of the decay- 

 ing organic matter and the microscopical organisms common to 

 standing water. Only one comment in favor of the generally con- 

 demned mosquito can be found and that is in regard to the larvae. 

 Comstock says: The larvae of mosquitoes are doubtless beneficial 

 insects, for they feed on the decaying matter in water, and thus act 

 as scavengers, and then he adds, but the annoyance caused by the 

 bites of the adult female more than balances this good. The length 

 of the larval life was found to vary under different conditions from 

 seven to fifteen days. 



At the last larval moult, the pupal stage begins. The pupa is 

 an ungainly looking creature resting quietly at the surface, tail-end 

 downwards and further distinguished from the larva by its big 

 head. This head is really the head and thorax of the insect fused 

 together. The pupa has also two breathing-tubes, instead of one, 

 rising, not from the tail-end of the body but from the upper side 

 from that portion known as the thorax. The end of the abdomen 

 is supplied with two broad flaps used for swimming, with which 

 by vigorous motions of the body the insect drives itself down into 



