144 



at all events during a shorter or longer part of their life. In 1920 when the 

 immense swarms of 0. communis and 0. proclotes were hatched, the temperature 

 suddenly fell for a fortnight, never rising above about 6 — 8 degrees Celsius. Im- 

 mense swarms of mosquitoes, females as well as males, were sitting in the grass, 

 flew up when the grass was moved, but never tried to bite. At the same time 

 Taraxacum vulgare and Cerasus padus were in blossom. About ten days after the 

 above-named mosquitoes were hatched, these two plants, especially Taraxacum, 

 were regularly visited by mosquitoes; on the meadows almost every flower had 

 one or two females of 0. communis and many three or four; the females were sit- 

 ting on the flowers and pierced their proboscides into the heads now here now 

 there. The phenomenon lasted for about eight days here in North Seeland; simul- 

 taneously with my own observations Mr. Kryger had an opportunity to make 

 quite similar ones on the large moors south of Copenhagen. Then we got fine 

 weather with a temperature of about 20° C, and in the course of a few days the 

 immense swarms rose, the higher temperature awaked their lust of blood, and 

 sojourn in the forest was almost made an impossibility. In the foregoing years I 

 have now and then, in the latter part of cold rainy periods, found a few mosqui- 

 toes upon flowers. In a cold rainy period from '^ 5 /vn to '/vm 1920 I was often 

 attacked by 0. lutescens and 0. canlans. It struck me that many of these specimens 

 were gorged with a fluid which could not be blood being clear like water. Squeez- 

 ing the females clear drops appeared. They were sweet like sugar and were un- 

 questionably honey. In the cold period many of the mosquitoes had been forced 

 to be vegetarians. 



The fact of the matter is unquestionably that the lust of blood of the Aedini. 

 at all events in our country, is dependent on the temperature, and that vegetable 

 matter, more especially in the cold spring months plays a much greater role in 

 the diet of the mosquitoes than we have hitherto thought. (See also Howlett 

 1910 p. 479). 



I have myself no observations with regard to the relation between mating 

 process, bloodsucking and egg-laying. Formerly most authors maintained that a 

 bloodmeal was necessary for the females to ripen their eggs; with regard to the 

 literature I refer the reader to Nuttall & Shipley (1902 p. 65). Now it has been shown 

 that females which were held upon a vegetable diet were also able to lay eggs 

 from which adults were reared in some cases (Sen 1917 p. 729; 1918 p. 620). 

 Neumann (1910 p. 27) has kept C. pipiens alive for two years in a large aquarium; 

 many generations have been hatched but they have got no nourishment. He further 

 maintains that also C. nemorosus is able to produce eggs without a bloodmeal but 

 in that case the eggs do not develop, and that Anopheles is also said to be able to 

 do so after hibernation. See also GrCnrerg (1907). Goeldi remarks that fer- 

 tilized eggs may remain dormant in a female for 102 days, if a feed of blood is 

 withheld. Macfie (1915 p. 205) has observed with regard to Stegomyia fasciata 

 that the first blood meal was taken by females on the second or third day 



