OBSERVATIOXS ON THE BIONOMICS OF STEGOMYIA FASCIATA. 



229 



In several of tlie experiments carried out with saline media it appeared that the 

 ■development of the mosquitos was accelerated. Pupae of approximately the same 

 age almost always hatched out into adults earlier in saline solutions than they did 

 in the controls in tap water (see experiment XIV. above). The same phenomenon 

 is illustrated in the following experiment :- — 



Experiment XV. 



Date. 



Tap water control. 





Medium containing 0'49 % NaCl. 



May 27tli 



to 



22 pupae of S. fasciata introduced. 



22 pupae of ^S'. fasciata introduced. 



June 6tli, 



1915 









June 4th 





First eggs laid this afternoon by 



First eggs laid this morning by the 







the mosquitos that 



have 



mosquitos that have emerged. 







emerged. 







June 7th 





First larvae seen. 





First larvae seen. 



June 16th 





No pupas yet. 





First pupa seen. 



Juns 18th 





No pupae yet. 





First adult emerged. 



June 21st 





First pupa seen. 







June 23rd 





First adult emerged. 







This acceleration of the life-cycle in media containing an unusually high percentage 

 of salt may be a natural reaction on the part of the larvae and pupae to protect 

 themselves from the injurious effects of the drying up of the pools or small 

 collections of water in which they w^ould naturally have been breeding. As a pool 

 of water dries up the concentration of its soluble saline constituents of course 

 increases, and this may serve as a warning to the mosquitos breeding in it that 

 they are in danger of being left high and dry. 



