LIFE HISTORY AND SEASONAL PREVALENCE 135 



tare of Indian hill stations, Gulicidcc larvae develop even 

 more slowly than in Italy. 



In Northern Europe all larvae and pupae that may not be 

 ripe for their remaining metamorphoses, perish during the 

 winter, but in Italy, according to Celli, the larvae of Ano- 

 pheles " hybernate " (CM., p. 78 and 166) and some, at any 

 rate, of the adult insects that appear early in the spring are 

 furnished by larvae that have passed the winter in that stage. 



I am nearly sure that the same is the case in Northern 

 India, though in a tank in my garden at Shahjahanpur, 

 where I had found them present in swarms on my arrival, 

 and which I had always kept supplied with water, so as to 

 keep them under observation, they suddenly disappeared 

 about January 11th, without any apparent reason, as the 

 severest part of the "cold weather" was already past. 

 Unfortunately I was unable to find any other pool, in which 

 to continue observations, as a long spell of drought during 

 the last three months of 1900, had completely dried all 

 such pools as had remained under natural conditions. I 

 have on one or two occasions noticed the larvae, though 

 abundant a few days before in all stages, disappear from a 

 pool in the same unaccountable manner, and strongly 

 suspect that this must have been due to the outbreak among 

 them of some epidemic disease. 



Although they were thus capable of maintaining them- 

 selves as larvae, no imagines were being produced, and for 

 six whole weeks not a single pupa could be found, though 

 carefully sought for ; nor, so far as I could judge, did the 

 individual larvae grow to any extent, as all sizes were present 

 from the first, and the large ones did not appear to become 

 more numerous. 



The lowest temperature ever observed in this tank was 

 56'' F. in the early morning, but the margin of temperature 

 inimical to pupiation must be a very narrow one as, after a 

 fall of rain accompanied by cloudy nights, during which the 

 night temperature could not fall to the usual minimum, the 

 higher temperature sufficed to bring about the appearance 

 of a few pupae. 



Now the rain had not perceptibly altered the depth of 



