169 



localities as well as in the third, where the fact was ascertained, the nursery, the 

 bedrooms and the servants' rooms were full of A. maculipennis', the people main- 

 tained that during night they suffered horribly from mosquitoes, and that their sleep 

 was disturbed by the insects. It has been maintained that .4. maculipennis every- 

 where round Silkeborg attacks man. This more especially holds good in autumn. 



Most probably the statement is quite correct. For all three localities it can be 

 pointed out that there is a want of cattle. In one locality, the great estate of Nor- 

 holm, the cattle was out of doors; the Anophelines have flown into the servants' 

 rooms and satisfied their lust of blood on man; of the two other localities one, 

 Silkeborg, is surrounded by water in an area where undoubtedly vast numbers of 

 Anopheles may be hatched and where the number of cattle to nourish the number 

 of Anophelines is but small; the third spot was at Gudenaa where the same is the 

 case; here the house was in possession of a fish farm with large hatching ponds 

 which contained plenty of Anophelin larva 1 but no stock of cattle. 



It seems therefore that in localities where special conditions prevail, A. ma- 

 culipqnnis nowadays also attacks man, but we have here only to do with excep- 

 tions; the rule is that this is not the case. 



i:i As A. maculipennis is now ascertained to be an inhabitant of our stables, 

 the question is if they may be regarded as quite harmless insects; I am not quite 

 sure that this is the case. More than once we have explored stables which only 

 contained two cows. When in such stables we are able to count about 100 .4. ma- 

 culipennis on a m 2 and may estimate the number of mosquitoes at many thousands, 

 and 90 % of them are blood-filled, it may really be a question if the cow is able 

 to produce the same amount of milk, whether the stable is mosquito-filled or 

 empty of mosquitoes. If I estimate the amount of mosquitoes in such a stable at 

 5000 only, a number which is unquestionably too small, it means that about 5000 

 drops of blood are hanging on the ceiling and walls. If then I suppose that this 

 number is almost unaltered from the 1st of June to the 1. Sept. and that the blood 

 is renewed every fourth day - - this is probably too little - - this again means that 

 the cows have been tapped of more than 100.000 drops of blood. If we further 

 suggest that 100 drops are about 5 can blood, this again means that the mosqui- 

 toes have tapped the cows of 5 liters of blood during the summer. I suppose that 

 this may be regarded as rather strong, at all events rather unnecessary, bleeding. 



It may in this connection be kept in mind that quite similar calculations have 

 been made by WiLHELMl (1917 p. (59) with regard to Stomoxys calcitrans, and that 

 Bishopp (1913) for the same species and from explorations in North Texas has 

 shown that loss of milk production owing to the same cause should be estimated 

 at 40—60 °/o. 



With regard to the Anophelines it may in this connection be remembered that 

 a study of the literature from Grassi (1900) up to our own day seems to show 

 that no conformity with regard to all indications as to the blood filling processes: - 

 how often they take place; the relation between egg laying and blood tilling; the 



l>. K. U. Vldensk. Selsk. Skr.. naturvidensk. og mathem. Afd. 8. Raekke. VII. 1. '>') 



