50 



I now feel convinced that all the mosquito-larva> which appear during the 

 winter or the first days after the ice has melted, all belong to 0. panctor, 

 O. communis, 0. prodotes. Later on, commonly not before 5/n — t/v a t a time when 

 the larva? of 0. punctor — communis are almost fullgrown, very small, newly-hat- 

 ehed larvae appear. These larvae are larger than those of 0. communis, the head is 

 yellowish-red, and the body brighter. As they are hatched later than 0. communis, 

 the volumina of water, in which the larvae and especially the pupae live, are often 

 extremely small, being often only a few deciliters. At the beginning of a dry period 

 the development may be shortened, the pupa stage not lasting more than a few 

 days. Very often I have observed the peculiar fact that the species which bites belongs 

 to 0. communis, where as the species which is hatched from pupa is O. cantons. 

 If we sweep the catcher through the vegetation, we shall see that all that we get 

 near the pond is 0. cantans which is sitting deep down in the grass near the ponds, 

 whereas the mosquito which makes our sojourn in the forest and round the 

 pond intolerable is 0. communis. Flying out of the dark shades of the wood, they 

 anounce their attack by their burz, their smell having directed their way. Their 

 real resting places were far away from the ponds on the trunks of the large beeches 

 and below their foliage. 



With us 0. cantans uses more than a fortnight to be able to sting. Then there 

 may be some weeks when 0. communis and 0. cantans attack simultaneously and 

 side by side; little by little 0. communis disappears and 0. cantans predominates. 



There is undoubtedly only one generation in the course of the year. The 

 larva is hatched in the middle part of April and the imagines about a month 

 later; the life of the imago lasts about three months; the eggs are not ripe before 

 two or three weeks after hatching; then the ponds dry out, and in summer (July — 

 August) the eggs are laid on the dry bottom; here they hibernate; when in autumn 

 the ponds get water again, this has no influence upon the hatching of the eggs. I 

 have never found a single O. cantons-larva in autumn, the eggs must undoubtedly 

 pass a freezing period before being hatched. 



The larva? live as the 0. co/nnm/us-larvae, in the surface, hanging down from 

 this by the sipho. - - Still I suppose that they are more pronounced bottom fee- 

 ders than those of 0. communis. 



In 1920, as cold and rainy weather was a hindrance to the hatching of 0. 

 communis, there was a week in which the larva-swarms in our forest ponds were 

 composed of almost equal numbers of 0. communis and 0. cantans; then the 0. 

 communis larvae changed into pupae, whereas the 0. canfans-larvae remained un- 

 altered for one or two weeks. Even then it was by no means difficult to distinguish 

 the 0. cantans larvae from those of 0. communis, the first-named being larger, 

 brighter and having a red head which immediately distinguished them from those 

 of 0. communis with their grey heads. 



With regard to the biology Breslau (1917 p. 524) states that there is only 

 one generation in the course of the year, that the eggs are laid singly or in small 



