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never found a single mosquito larva. As late as April of this year I have travelled 

 over a great part of my area of exploration and visited several hundreds of tempo- 

 rary ponds scattered over the fields and meadows, and only found mosquito larvae 

 in ten of them. This is in contrast to the conditions in the forest ponds, where 

 almost every single pond in spring contains larva? often belonging to many species. 

 There is also this difference between the mosquito life in forest ponds and ponds 

 of the plains that the first-named almost always teem with myriads of mosquito 

 larvae whereas in the last named — apart from the brackish water pools — we 

 often find only very few specimens almost always belonging to the above- 

 named species differing from those which inhabit the forest ponds. 



Finally I wish to call attention to the following results which, as far as I know, 

 are in accordance with those of all the authors who have made a more thorough 

 study of the biology of the mosquitoes. It is often maintained that the attacks of mos- 

 quitoes are more troublesome in the vicinity of large lakes, and that the mosqui- 

 toes are hatched especially in them. The fact is that our mosquitoes are 

 never hatched in lakes, but all belong to very small pools, most of them living in 

 ponds which are dry or frozen for about eight months of the year. Another thing 

 is that they often occur in the small ponds which border larger watermasses, and 

 which are cut off from them. 



Further it has often been stated that the mosquitoes are actively able to 

 spread over large areas. For all our Danish Culicines this supposition is, accor- 

 ding to my opinion, not correct. They are almost all remarkably stationary animals; 

 many of the colonies never leave the vicinity of the pond where they are hatched; 

 we are only attacked when we place ourselves at the borders of the pond; this 

 especially holds good for Aedes cinereus. Where small, sharply defined woods are 

 spread over a rather wide area f. i. in North Seeland, it often happens that different 

 species are prevalent simultaneously in the different forests. Most of us will also 

 observe that we are very rarely attacked in the open country, but that we are sub 

 ject to even very violent attacks if we seek the shade in one of the woods; the 

 more attentive observer will further notice that if we are attacked simultaneously 

 in the open country and in the forest, the attack in the former locality is almost 

 always due to 0. lutescens, whereas quite different species are prevalent in the 

 forests. In my opinion everything seems to indicate that our mosquitoes are really 

 very stationary animals, only rarely leaving the forest where they are born; per- 

 haps the mosquitoes of the open meadows have a somewhat greater power of 

 spreading, at all events passively, owing to the wind; this would most probably 

 hold good with regard to the brackish water species, more especially 0. caspius 

 which leaves the coast after hatching, flying landwards in search of man and 

 cattle. With regard to some of the Anopheliiue — in our fauna more especially 

 A. bifurcatus — the case is different. (See the following). 



It is a well known fact that the mosquitoes in different parts of the world 

 occur in countless numbers and make the sojourn in these places almost intolerable 



