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houses, cellars and sheds; but this is undoubtedly not correct. In 1916 on one of 

 the last days in April, I was examining an old hollow beech and to my astonish- 

 ment saw that many T. annulala were sitting in the bright sunshine on the wind- 

 sheltered part of the trunk. I prodded the hollow part of the trunk with a walking 

 stick and the mosquitoes rushed out of the trunk like smoke; all were females, 

 which undoubtedly had their winter-quarters there. When I passed the same old 

 beech late in Oktober 1919, I again saw many imagines of the same species but 

 now males as well as females, sitting and flying round the entrance to the hollow 

 part of the trunk; no doubt they were seeking their winter quarters there. I lost 

 the opportunity to see the egg-rafts and the egglaying processes, but in July — Au- 

 gust I found the large greyish larva? among the swarms of C. pipiens larvae; they 

 were hatched in Cement-reservoirs in dairy-farms and in cow-houses in farm yards; 

 the number is always rather small, perhaps about one T. annulata to a hundred 

 C. pipiens. They are found as larvae and pupa? much later than C. pipiens (till 20/ x 

 1918). This is in accordance with the fact that the imagines fly remarkably late, 

 and that I have often found the imagines sitting out of doors the last days of Oc- 

 tober, behind shutters, below veranda-staircases etc. I suppose that the imagines 

 pair before winter and then die out; in spring I have never seen a single male. The 

 development by no means always takes place in our houses; I have found them 

 together with larvae of C. pipiens, in ditches mainly consisting of urine near gates 

 sheltered by old oaks below which the cattle regularly sought shade against the 

 burning sun. But, apart from these unsavory localities, I have also found them in 

 great numbers in a little pond covered with Lemna but with very decaying mud 

 in the bottom. This pond has been under regular observation for three years, 1918 

 — 20, but T. annulata was only to be found in 1918. 



The pond was visited for 0. cantans from April to June in 1918 and during 

 that time I did not get a single T. annulata. When I visited the pond 10 /vn to 

 search for the rare larva of Rana agilis living in the same pond, I was rather asto- 

 nished to see that the pond now contained a great many grey, halfgrown larva 1 , 

 which later on gave T. annulata. The larva? were not hatched before the middle of 

 August. I always found small and large larva 1 among each other, and I got the 

 impression that the egg-laying took place at all events in September; curiously 

 enough I could never find the egg-rafts. Also in ponds near Hillerod have I found 

 T. annulala larva? in September — October; one of them had clear brown peaty- 

 water; they lived here till 12/x, when the pupa? appeared, giving imagines in my 

 laboratory on 17 /x. 



From these observations we are able to ascertain that T. annulata is hatched 

 in the cement-reservoirs indoors, as well as in ponds in Nature itself. I am inclined 

 to interpret the above-named facts in the following way. In our country T. annu- 

 lata has two generations. The hibernating generation appears in September — Octo- 

 ber, hibernates in our houses, and lays its eggs indoors in stables elf. ; from these 

 eggs appear the summer generation, which disappears from our dwellings and lays 



