148 



to all these species, that in the bloodsucking period there are really rather few 

 days, in which they try to satisfy their lust of blood; these days coincide with 

 certain meteorological data, great humidity of the air, a high temperature and rather 

 low barometer. When on such a warm damp day, especially about sunset, one 

 has witnessed the enormous masses of mosquitoes which from all sides dart upon 

 the wanderer or the horses, and have seen the eagernes with which the attack 

 takes place, one cannot get rid of the supposition that it is only a very small part 

 of the whole crowd of mosquitoes which really gets blood. More especially in cold 

 summers with heavy rains, falling in the main period of the Hying time of the 

 above-named species, I should suppose that out of the millions only a very few 

 get a blood meal. A factor which helps the mosquitoes is their longevity, and that 

 their life is prolonged if blood meals cannot be obtained. This is in accordance 

 with my own experience, acquired in Nature herself; in very hot summers the 

 mosquito plague is in the main at an end by the latter part of July, and all spring 

 livers disappear before July, in wet summers, such as 1919, the mosquito plague 

 lasts till the latter part of August and spring species such as O. communis are on 

 the wing and biting as late as the middle of August. As mentioned above accor- 

 ding to my opinion there can be no doubt about the fact that the attacks in Au- 

 gust do not come from new broods or generations, but are caused by the specimens 

 which are hatched in spring, but have had no opportunity to get blood. 



In the literature a few examples are mentioned of males which are able to 

 bite; this is said more especially with regard to Aides calopus (Ficalby cited from 

 Howard, Dyar and Knab 1912 p. 109), but these authors suppose that the obser- 

 vation is wrong. Of our mosquitoes it is especially the males of 0. nemorosus : 

 which are said to bite. Stiles was bitten by an 0. nemorosus with long antennae 

 (H. D. K. 1912 p. 109), and later on Edwards (1917 p. 216) has been subject to a 

 similar attack. This last-named author shows that none of the three examined 

 males were normal, and that all three had one or more female characters on one 

 or both sides of the body. 



With regard to the blood-nourishment and its signilicance for the ripening 

 of the eggs I wish to make the following remarks: 



If we take an 0. lutescens, newly hatched, and make transversal sections of 

 the abdomen, we shall find a well marked fat body, filling the greater part of the 

 abdomen and a very thin alimentary canal, only occupying a very small part of 

 the abdominal cavity; the walls of the canal show the well known deep folds, the 

 transversal sections therefore showing a starlike figure. If then a fortnight later we 

 let the mosquito suck blood, and now lay the abdomen in transversal sections, we 

 see nothing of the fat body. The abdomen is enormously expanded; the ventral re- 

 servoir for the blood fills the whole abdominal cavity only leaving a very incon- 

 spicuous space for the nervous system below and the heart above. 



If further we let an 0. lutescens suck blood, keep it for eight days in a hat- 

 ching cage, kill it and take transversal sections of the abdomen, we shall again get 



