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from the swarm ; it was very interesting to see, how straight the lines were, along 

 which these mosquitoes made their way into the swarm ; the mosquitoes were al- 

 ways females of C. pipiens; it was as if by some magic power the insects were forc- 

 ed to fly directly into the swarm of dancing males. Undoubtedly they were direct- 

 ed by the sound issuing from these males which I have often heard formerly and 

 which others, standing near me, heard very distinctly. Having lost my hearing for 

 very high notes, I am probably not able to hear these notes any more. 



The moment a female had reached the swarm, a great excitement was notice- 

 able in it. Now here, now there, a ballshaped, thicker, little cloud was observed; 

 a few seconds later two mosquitoes, male and female, dropped out of the swarm, 

 slowly sank down into the grass or retired some meters from it carried by the slight 

 sunset-breeze. I could never directly observe that the mating position was end to 

 end, as indicated by Knab (1912 p. 122); the insects were always curled up in a 

 ball and very soon reached the grass. Here the act was accomplished in the course 

 of a few seconds, after which the mosquitoes tlew away. 



In the first part of October we got a period of bad weather; the mosquitoes 

 disappeared; undoubtedly the males died off, and the females retired to the deep 

 cellars, the ceilings of which were covered with C. pipiens. In their spermateca the 

 spermatozoa survived the winter, next year giving rise to new generations. In this, 

 as in many other cases, where the males die off in autumn, and the females keep 

 and preserve the sperma in their bodies, I find our customary phrase, that the 

 males die off rather incorrect; I should suppose that it was more adequate to say 

 that the males only hibernated in the spermatozoan stage; this would be more in 

 accordance with the expression we use with regard to all those species, which die 

 out before winter, and with regard to which we commonly use the term that they 

 only hibernate as eggs. 



With regard to 0. fletcheri I have made the following observations. On is/vi 

 I was standing on the southern coast of Lolland near Aalholm Castle, on a little hill 

 covered with trees and lying in a vast fen, covered with reeds. Below the trees 

 the ground was covered with more than one meter high nettles. It was near sunset 

 at seven o'clock. The weather was calm; Tp. 20° C; the day had been very warm. 

 Enormous masses of 0. fletcheri were sitting in the reeds; as soon as I came down 

 upon the little path, hundreds of females rushed upon me. Studying the nettles I 

 then saw that most of the leaves of the nettles either on the edges or on their tips 

 carried males of mosquitoes undoubtedly 0. fletcheri; the mosquitoes hung on to 

 the edges of the leaves by means of the two first pair of legs, the hindlegs were a- 

 straddle in the air and were now and then moved in circles; the females almost 

 always sat under the leaves. When I now moved the nettles with my walking stick, 

 both sexes arose, and to my great satisfaction I saw that if they touched each 

 other during the flight, pairing immediately took place. For three consecutive even- 

 ings I now observed the phenomenon during the time from 6V2 to 7 o'clock. At 

 li 1 i' o'clock Ihc males and females sit on the leaves as mentioned above, about 7 '/», 



