MOSQUITO BIOLOGY 195 



Another collector reports the hatching of the eggs very soon after a 

 pool becomes water filled, and the rapid development of the larva : "On 

 one occasion it began to rain on Monday morning and water soon col- 

 lected in the bed of a dried up pond. In the deepest place there was a 

 patch of damp mud with a rotten log lying in it. On Tuesday there 

 were thousands of Aedes sylvestris larvae about one-eighth of an inch 

 long. Pupae of both forms had developed by Friday, and on Monday 

 all had enlarged." 



The larvae are immense for wrigglers and are at once recognizable 

 by their size. Unlike others of this series they are predatory and feed 

 on other mosquito larvae ; if there are not enough of other kinds pres- 

 ent they turn cannibals and eat each other until some are full grown 

 and complete their transformations. Their appetite is enormous and 

 they feed continuously. Small larvae are swallowed entire ; the larger 

 are seized just below the anal siphon or breathing tube to choke them, 

 and when the struggles cease are devoured to the head. The larvae are, 

 therefore, scattered as compared with those of other mosquitoes. One 

 collector found one to every thousand Cvlex and Aedes when both 

 occur together, but that of course is subject to any amount of varia- 

 tion. Another collector found pools swarming with small Aedes vexans 

 and a goodly population of Psorophora among them. A few days later 

 only Psorophora remained, and these were scattered and difficult to 

 find. There is no greater enemy of or more effective check to, other 

 mosquito larvae, than PsoropJwra, and its rank as a pest is not suf- 

 ficiently high to counterbalance the benefits received from it. Unfortu- 

 nately it has its limitations. It occurs usually in temporary pools or in 

 pools which have been dried out previously to kill off all fish and similar 

 enemies, and its habits of attacking and devouring its own kind when- 

 ever opportunity offers, prevents anything like a great increase in its 

 numbers. 



As a rule, perhaps, woodland pools or those at the borders of wood- 

 land are favored as breeding places, but I have found and received 

 larvae from more open pools, even from entirely unsheltered holes near 

 the banks of the Raritan River, so that it can scarcely be said that 

 this is a real woodland mosquito. There is scarcely a county in the 

 state from which the early stages have not been sent in. 



