Other characteristics of larva and eggs. 



3. The resistance of larvce to drying. Dr. Christophers also 

 found that larvae could remain alive on soft mud even after exposure 

 to the sun for several hours. If the mud had so far dried as to 

 lose its glistening surface the larvae were found to be dead. 



4. The duration of the larval stage. Dr. Liston found that, 

 under suitable conditions, " anopheles " larvae became pupae in about a 

 week, but that with an unsuitable or deficient food-supply they re- 

 mained as larvae for more than a month. At Mian Mir in Septem- 

 ber (the most favourable month), Dr. Christophers found that A. 

 rossi did not pupate until the twelfth day after the eggs were laid. 

 No difference was noted in the case of shallow or deep pools, 

 although the temperature of the water in the shallow pools was 

 high, viz., 96 F. to 102 F., while that of the deep pools was only 

 90 F. or less. The adult insects emerged two days after pupation, so 

 that fourteen days ( two in the egg form, ten in the larval form and 

 two in the pupal form ) would appear to be about the minimum time 

 required for the development of rossi from the egg to the adult stage. 

 The least time in which culicifacies developed from the egg to the 

 adult stage was thirteen days. The same observer remarked that 

 " anopheles " were slower to develop than any other kind of mosquito, 

 taking three days longer than Oulex and four days longer than 

 Stegomyice. 



In the winter months the development of larvae may be almost 

 indefinitely delayed, and, as already mentioned, the larvae of some 

 species may remain without developing into pupae throughout the 

 whole winter (hibernation of larvae). Whether this is due to the 

 temperature of the water being lower, or to a difference in food- 

 supply, is not known, but the experiments of Dr. Christophers 

 recorded above would seem to show that the temperature of the 

 water has little or no effect. There is also a great difference 

 between different species in this respect, for in the Punjab while 

 the larvae of culicifacies remain in a hibernating condition 

 throughout the winter, those of fuliginosus develop into pupae 

 and adults even in the coldest months. 



58] 



