77 



the bottom of the ponds were covered with spruce-needles; the depth of the water 

 was only about a decim., and the area of the pond about fifty yards. 



In regard to its short sipho and its black colour it differed very much from 

 C. morsitans, the only mosquito larva which was common at this season; a closer 

 examination of the sipho further showed that it could not be 0. rusticns; that the 

 larva would only be that of 0. communis did not occur to me. It was therefore to 

 be expected that the larva must be a new one. In the time from 15/x to *5/xi the 

 ponds were often visited. The temperature fell from seven to two degrees; at that 

 constantly sinking temperature, and in a pond which never got a single of the 

 really very few sunbeams of the season, these larvae reached their maximum size; 

 at the water temperature of 2 C. the larvae metamorphosed into pupae. At an air- 

 temperature of only 4 C. and a water temperature of 2 C. I saw the imagines in 

 nature come out of the pupae, very slowly fly a few yards and settle themselves 

 on the cushions of Sphagnum near the borders of the pond. The males appeared 

 first, a few days later the females. By 15/xi came a short frost-period; the ponds 

 were ice-covered, and all the pupae in the pond were killed. In December the ponds 

 thawed again, but not a single larva or pupa could now be detected. In the time 

 from 15/x to i-Vxi I visited many similar forest ponds lying in forest of spruce firs, 

 and I often found the same larvae in these ponds; these were always in very cold 

 localities where the damp autumn-fogs hung under the spruces almost the whole 

 day. Though I especially paid attention to that point, I could never see the mating 

 process; but opening the Sphagnum cushions near the ponds, I found the female 

 sitting there very indolent and half sleeping. The larvae had all blunt scales in the 

 comb and one single hair in the upper and lower frontal tuft. The colour of the 

 larvae and pupae was black as tar, but apart from this colour they were in- 

 distinguishable from the typical 0. communis larvae. The next spring, in the first 

 part of April, when the ponds were still partly covered with ice, I examined the 

 locality and found the water teeming with minute larvae. By 8/y they contained 

 enormous masses of larvae and pupae, on iVv the pupae were hatched. 



If now we compare the imagines from the autumn of 1918 with those from 

 the spring of 1919 and 1920 we shall see that the first-named are larger, darker 

 and more hairy; a closer examination will however show that tenable differences 

 between the two groups of imagines hatched in autumn and spring do not occur; 

 both belong to the same species, our common 0. communis; I do not think that 

 the imagines have hibernated ; most probably they have died off, imagines in spring 

 deriving from eggs which have not been hatched in autumn. 



For a time I thought that in the autumn-generation I had had 0. nigripes 

 Zett. before me. This was more especially the case because only a few kilometers 

 from my localities STAEGER (1839 p. 553) in the Royal Deer park near Copen- 

 hagen has indicated that he has found 0. nigripes. Owing to the peculiar fact that 

 the larvae metamorphosed at temperatures between 4 and 2 C. and that the ima- 

 gines appeared at the same temperature, in this tract, which was quite extraordinary 



