March, I9I3-] GrOSSBECK : MOSQUITOES AND ENVIRONMENT. 59 



York Culex pipiens, rcstiians, salinarins, melannnis, perturbans, terri- 

 tans, probably saxatilis, and Uranotccnia sapphirina — eight in all — 

 deposit them in rafts. In order to insure safety to the larvae two 

 things must be observed by the parents : running water must be 

 avoided, else the eggs will be washed away, and if in no other way 

 destroyed by being carried to those ever ready for so dainty a morsel 

 as an egg boat ; and, the eggs must be deposited in a nook already 

 comparatively free from enemies. Thus, these species are limited 

 first to quiet water, and second to protected places in that quiet water. 

 With regard to this latter nothing can be better than a pool so tran- 

 sient in character as to exclude the breeding of practically all other 

 insects. When this can not be had the edges of shallow bodies are 

 selected, particularly where protected by vegetation, rocks or debris. 

 Such conditions are suited to most of the species in the egg-boat cate- 

 gory, but other as yet unknown reasons induce some to select the 

 fouler water (pipiens) and others (restuons, territans, etc.) the 

 cleaner water. One species {salinarius) will select only salt water, 

 and three others only permanent bodies of fresh water. The reason 

 for the selection of permanent bodies in two instances {perturbans 

 and melanurus) is known: the larvae pass the winter in the larval 

 stage and hence any water which would disappear during the fall or 

 winter would cause the larvae to perish. With Uranotccnia sapphi- 

 rina, the third species, the reason for the selection is not apparent. 



The species which deposit their eggs singly may be placed in two 

 distinct groups : those that deposit their eggs on the surface of the 

 water and those that deposit them in the mud in depressions likely to 

 be water filled. Only three species are positively known to have this 

 last mentioned habit, all of them occurring on the salt marsh. It is 

 well known that the salt marsh is subject to periodic inundation and 

 desiccation. After such an area has been flooded all the pools are 

 filled with larvae, and a week or two later the adults emerge; but 

 egg-laying does not begin until the meadow has become largely dry, 

 when the mud is littered with eggs which remain unhatched for a 

 month or a year, or several years if necessary, until covered by water, 

 when the young larvae emerge. 



Many species are known to lay their eggs singly on the surface of 

 the water but the group consisting of these species may again be 

 divided into those of which the eggs hatch in a day or two as in the 



