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pairs in mating position in the air. I was standing with my camera in my hand, 

 and more than once I could see the dancing pairs, on the focussing screen of my 

 camera, but it was too dark to get a photo of them. At 8.30 the phenomenon abated, 

 and at nine o'clock I saw no more dancing pairs. 



In the forest which borders some of my experimental ponds near Hillerod 

 (Stenholtsvang) I have often observed the swarms of 0. communis and prodotes. 

 The swarming always took place about a fortnight after the mosquitoes were hatch- 

 ed; the swarms consisted only of from twenty to fifty individuals; but of such 

 small swarms there were many hundreds around the ponds; they were always 

 standing in the small open spaces between the trunks, mainly from one to two 

 meters above the ground; they could best be observed when suddenly sunbeams 

 fell down between the trunks. In the swarms the single individuals kept their 

 vertical position, only slowly gliding forwards and backwards in the same plane. 

 Also with regard to this species did I see the females from the shade of the forest 

 steer into the swarm and after a short battle drop out with a male. The mating 

 process took place in the deep shadow of the trees at every time of the day. 



With regard to Theobaldia annulata Mr. KRUGER has sent me the following 

 interesting observation. 



"On October the thirteenth a little past five, after noon, I arrived at Gentofte. 

 I then saw something that looked like smoke on two chimney tops on one of the 

 villas which I passed. A peculiar undulating motion in the smoke made me pay 

 a little more attention to the phenomenon. I then observed that it was two mos- 

 quito swarms which were standing over the chimney tops. A few moments later I 

 had opportunity to ascertain that all the cottages in the little town had mosquito 

 swarms over the chimney tops. By means of a fieldglass I saw that all the swarms 

 consisted of mosquitoes, that all were males and most probably all Culicines. Every 

 swarm consisted of about 200, rarely about 400 specimens. The swarm undulated 

 to and fro; the single mosquito moved forward and in small jerks back and down- 

 wards. The swarm was always standing a little aslant from the chimney top. All 

 the swarms were directed eastward, and all the mosquitoes facing in the same 

 direction; most probably because a very faint breeze seemed to come from this quarter. 



Chimney tops from which it smoked had no swarms. My daughter had ob- 

 served the phenomenon before my arrival at my house; she thought that it began 

 at 5 o'clock. The swarm building was always begun at the gable head, but at sun- 

 set the swarm was standing over the chimney tops. Ascending the roof of my house 

 I got some of the mosquitoes: they were T. annulata, all males. At six o'clock the 

 swarm disappeared; the weather was beautiful, the air warm and soft; no wind; I 

 could never hear any sound arising from the swarms". The observation corrobo- 

 rates the often mentioned peculiarity that the swarms are formed over elevated 

 objects: hay cocks, persons walking over prairies and meadows, cattle etc. 



