143 



to people and mammalia; this is f. i. the case in the arctic region and in many 

 parts of the tropical world. But the plague is serious also in a great part of the 

 temperate zone and a long series of papers dealing with mosquito swarms and mos- 

 quito attacks have appeared. Some of them are cited in the following. Swinton 

 (1768); Dale (1833 p. 543), Boll (1858 p. 186), Hagenow (1860 p. 457), Weyen- 

 bergh (1871), Smith (1890), Douglas (1895 p. 239), Blummel (1898 p. 15), Whee- 

 ler (1894 p. 373), Sintenis (1891), Knab (1906 p. 123), Weber (1906 p. 38), 

 Meissner (1908 p. 8), Germar (1913 p. 137, 1917 p. 336), Zetek (1913 p. 5). 

 Some of these papers deal with phenomena of more biological interest; I more 

 especially refer to the paper of Zetek, concerning the determination of the flight 

 of the mosquitoes and that of Wheeler dealing with anemotropical phenomena. 

 Connected with the swarmbuilding phenomena are also the peculiar auditory organs 

 described by Johnston (1855 p. 97) and Mayer (1874 p. 577). 



In our own country we only rarely have occasion to observe large swarms of 

 Culicidw; it is perhaps mainly the case with O. caspius, but for my part I have not 

 had an opportunity to make any observation of that kind. In recent years we have 

 received many accounts, especially from Central Europe, relating to the mosquito 

 plague, and a long series of papers dealing with the means by which the mosqui- 

 toes should be destroyed have appeared. I more especially refer to the following 

 papers: Bresslau & Glaser (1918 p. 290 and p. 327); Eckstein (1919 p. 93 and 

 p. 530), Sack (1911); Teichmann (1919 p. 118), Bresslau (1917 p. 507), Prell 

 (1919 p. 61). 



In my own country we have hitherto never tried to destroy the mosquitoes, 

 and in my opinion the plague is not so great either that such a destruction should 

 be necessary in most cases. I only wish to make an exception with regard to .4. 

 maculipennis in our stables. See later. 



b. The Blood-sucking Habits of Culicines. 



As pointed out by almost all authors from recent years, the mosquitoes have 

 originally lived upon a vegetable diet, plant juices, nectar etc. As well known all 

 the males are still exclusively vegetable feeders, the very few, rather doubtful, ex- 

 ceptions will be mentioned later on. This also holds good for probably more than 

 half of all the females of the mosquitoes; a long series, mainly of tropical genera, 

 are, as far as we hitherto know, exclusively vegetable feeders in both sexes. I refer 

 especially to Howard, Dyar and Knab (1912 p. Ill) and to a paper by Knab 

 (Mosquitoes as Flowers Visitors 1907 p. 215) where the whole of the earlier litera- 

 ture with regard to this subject is cited. Now and then it has been stated that also 

 some of the European species may be found upon flowers; this is more especially 

 the case with T. annulata. From observations from the last three years but especi- 

 ally from 1920 I am inclined to suppose that the meteorological conditions are 

 able to force the mosquitoes, more especially all the Aedince, to be flower visitors 



