91 



leaves and other material, as well as defective grading of gutters, pro- 

 duces conditions similar to those of the transient pools, so important 

 to the present mode of life of mosquitoes. 



Ninth. That the hibernation (i. e., where mosquitoes hibernate or 

 winter in a specific stage of their development) takes place in the spe- 

 cies we have studied in the egg and adult conditions. Dr. John B. 

 Smith calls attention to the hibernation of two forms in the larval 

 stage, but up to the present these species have not been observed in 

 Louisiana. Several >pecies keep on breeding through the winter, but 

 development is slower and fewer broods occur, owing to scarcity of 

 food and relatively lower temperature. Even with some of the true 

 hibernating forms long warm spells may bring the stages out of win- 

 ter quarters. From the above it is plain that mosquitoes are not uni- 

 form in seasonal appearance. Some are more abundant one season 

 than another and some may continue longer than others when they do 

 appear. As' certain species are specific germ carriers, it is essential 

 that the seasons of different species be carefully studied and tabulated. 



T>nth. — We have not found that any species of mosquito will 

 deposit eggs upon anything other than water. Even with C. sollici- 

 tans, under a variety of conditions, we have not been able to in any 

 way corroborate Dr. John B. Smith's supposition that ('. sollicitans 

 lay eggs upon marsh grass. The possible explanation is that the eggs 

 of this species are frequently left high and dry by the receding or 

 evaporation of the water upon which they are deposited. 



SOME OBSERVATIONS UPON TWO SPECIES OF PSOROPHORA. 



The summer of 1902 produced many unusual conditions for the devel- 

 opment of those aquatic insects that are dependent upon small ponds 

 or pools for their perpetuation, and also gave adequate opportunity 

 for the study of the adaptability of such forms in overcoming what 

 are regarded as unfavorable environments. Certain sylvan mosqui- 

 toes were observed to become very numerous in a few days after heavy 

 showers, even though a drought of three months prevailed previous to 

 the rains. Prominent among the mosquitoes observed were two -pe- 

 des of u gallinipper" {Psorophora ciliata and P. howardii). The nat- 

 ural conclusion to be drawn was that the eggs of these species, as well 

 as of Conchyliates rmtsicus, which was invariably found with them, lay 

 un hatched upon the ground during this prolonged dry spell. Hence 

 several Psorophora breeding places were carefully watched, and when 

 rain fell in sufficient quantity to till the ponds under observation larva* 

 could always be found a few hours after. Our investigations were 

 continued. The conclusion was reached that all of the eggs did not 

 hatch with the first rainfall, but that the alternation oi dry and wet 

 weather finally hatched all the eggs that had been deposited the pre- 



