137 



eight months or even more as is the case with C. morsitans. With regard to sex 

 differentiation see also ADIE (1912 p. 463 and 865). 



Having now in the foregoing worked out the main poiixts in the biology of 

 our Danish mosquitoes I have in the table on p. 136 tried to sum up the results 

 of my investigations and hereto attach the following remarks. From a biological 

 point of view the Danish Culicidse are referred to three different groups. The first 

 and the greatest contains all the Aedini with the three genera: Aedes, Ochlerotatus 

 and Finlaya; only one species 0. rusticus belongs to the second group. A charac- 

 teristic of the first group is that all the species winter exclusively or mainly as 

 eggs. The species often spend more than seven months in the egg stages, the 

 other stages are all restricted to the five summer months. Of these the larva 

 stage only lasts from four to six weeks and is commonly restricted to April May. 

 The imago stage lasts from the latter part of May to August, for some species, f. i. 

 0. detritus, only two months in autumn. In most of the species there is therefore 

 only one generation. Two generations occur regularly only in two species: the 

 brackish water mosquitoes: 0. caspius and 0. curriei. Our most common species O. 

 communis with regard to its life history differs very, much in the different localities; 

 in most of them it is in accordance with the other Aedini but it may have two 

 generations and is able to survive both as larva and as egg, probably also as imago. 



In rainy summers most of the species which regularly possess only one gene- 

 ration may probably get a second generation; this may especially be the case with 

 0. lutescens; all in all this generation is very insignificant in comparison with the 

 spring generation. Apart from the above-named exceptions I for one am inclined to 

 refer the main part of almost all our Aedini larvae from July and later on, to eggs 

 which belong to the same generation as the spring generation, but which have been 

 deposited under bad hatching conditions. 



The group contains the pronounced dwellers in the drying ponds which often 

 only possess water in the time from the snow-melting period to June. 



All the Danish species are pronounced blood suckers attacking man as well 

 as horses and cattle. It is just among the members of this group that man has 

 some of his most tormenting enemies among the mosquitoes. 



Some of the species are probably rather short living as imagines but most of 

 them live remarkably long, about three months or more, especially in damp summers. 

 It is a matter of fact that different species of Aedini hatched as imagines in April 

 May contain eggs the whole summer till late in August or even in September; this 

 is the case with 0. cantans, annulipes, excrucians, lutescens and perhaps other species. 

 The eggs are laid singly, never in batches, probably always upon wholly dry land. 



During the whole summer all the temporary pools of the forests, and mea- 

 dows are normally dry or moist but covered with dry leaves or grasses. Just in these 

 localities which to a human eye are often almost inseparable from the surrounding 

 ground, and which never get stagnant waters, the countless number of individuals, 



L>. K. D. Vider.sk. Selsk Skr ., naturvidensk. og mathern. Afd. 8. Raekke, VII, 1. 18 



