OBSERVATIONS ON THE BIONOMICS OF STEGOMYIA FASCIATA. 



097 



C. decens was breeding they were all killed within four hours, and in another medium 

 containing 1,600 parts of chlorine (2 6 per cent. NaCl) in which 0. irritans was 

 breeding they were all killed within 16 to 20 hours. 



In another experiment larvae of C. fatigans were transferred from the medium 

 in which they had been breeding, which contained only 6 parts of chlorine, to a 

 medium in which 0. irritans was breeding which contained 1,600 parts. All the ten 

 larvae transferred were dead within five hours. As on another occasion larvae of 

 C. fatigans had been found breeding in water containing 1,600 parts of chlorine, this 

 result seemed to lend support to the view that the action of the salt on the larvae 

 was due to the hypertonicity of the solution. It also suggested that it might be 

 possible to breed a race of S.fasciata that would tolerate a high percentage of salt. 



Eggs of S.fasciata, recently deposited, were therefore introduced into (A) a medium 

 containing 4 "3 parts of chlorine in which S. fasciata larvae had been found breeding, 

 and (B) a medium containing 1,400 parts of chlorine (equal to 2 3 per cent. NaCl) 

 in which 0. irritans had been found breeding. The details of the experiment were 

 as follows : — 



Experiment XIII. 



Day of 



the 



Medium containing 4' 3 parts 



Medium containing 1,400 parts 



experiment. 



of chlorine. 



of chlorine. 



1 





Ten eggs of S. fasciata, of a batch 



Twenty eggs of the same batch 







laid yesterday, introduced. 



introduced. 



3 





First larvae (three) hatched. 



No larvae have hatched. 



7 





Six larvae have hatched. 



No larvae have hatched. 



10 





Four larvae and t^^o pupae 



present. 



No larvae have hatched. 



11 





First adult emerged. 



As no larvae had hatched the eggs 

 were transferred to a medium 

 in which 8. fasciata was breeding 

 naturally. 



15 





Two adults have emerged ; four 

 larvae remain. 



No larvae have hatched. 



23 





The last of the original six larvae 

 emerged as an adult mosquito. 



No larvae have hatched. 



27 





The first batch of eggs -was laid. 



No larvae have hatched. 



Not only did the eggs fail to hatch out in the medium containing the high percentage 

 of salt, but after being immersed in it for ten days they were apparently so much 

 affected by it that they failed to hatch when transferred to a natural S. fasciata 

 medium. The eggs in fact had been killed by the medium containing 2-3 per 

 cent. NaCl. 



Following the same line of thought, pupae of S. fasciata were placed in jars 

 containing (A) 2 per cent, salt solution, and (B) tap water ; and when the mosquitos 

 hatched they were fed regularly with honey and blood, and a careful look-out kept 

 for the appearance of eggs (see experiment XIV.). 



