LIFE HISTORY AND SEASONAL PREVALENCE 127 



According to Meinert, the ova of Corethra are laid in 

 flat, round, jelly-like masses, each containing from 100 to 

 150 eggs, but Miall describes them as arranged in spiral 

 lines, so as to form a gelatinous sheet. We have no in- 

 formation as to the eggs of the other genera, and as a 

 matter of fact, our know^ledge on this point is very scanty, 

 and further observations are much required. 



The insects pair towards evening. The males assemble 

 in large numbers, flying hither and thither without travel- 

 ling far, and the females appear among them in smaller 

 numbers, so that the moment one appears she is clasped 

 by a male, allowing themselves to float in the air, or flying 

 together. The coupling only lasts a few moments, and 

 when it is completed the pair separate, and the fertilised 

 female proceeds to deposit her eggs. 



As already remarked, the time taken by the ova to hatch 

 out depends upon the species and on the circumstances of 

 its environment, but, in most, may be said to be about three 

 or four days. Even when newly escaped, they can be 

 easily distinguished by the naked eye, if favourably lighted, 

 as black dots with a transparent, wriggling tail. Being 

 mainly air-breathing animals, though it is possible that the 

 anal papillae may aid in respiration, by acting as gills, they 

 cannot remain under water for any length of time, and all 

 species pass the greater part of their time at the surface, 

 lying so that the respiratory opening is open to the air. 

 The larvEe of Culex, especially those species which possess a 

 long respiratory syphon, pose themselves in a nearly ver- 

 tical position, as if hung from the surface of the water, as 

 is well shown in the following illustration, which was 

 photographed from living larvae and pupae by my friend, 

 Mr. Royle, of Kosa, N.W.P. 



The larvae of Stegomyia, whose breathing tubes are 

 very short, lie much more obliquely, their position approach- 

 ing that of Anopheles, but this cannot be looked upon as a 

 generic peculiarity, as those of C. pulchriv enter , which have 

 an equally short syphon, take up the same position, which 

 is presumably simply necessitated by the shortness of the 

 tube. The species figured by Christie in his useful little 



