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that given by Roubaud; such an explanation I have tried to give but I do not 

 know for how wide areas my explanation holds good (p. 182). 



Upon one of the last pages in his work Roubaud. and according lo him lev 

 Sergents (p. 222) has corroborated an idea which I have had but which I was 

 unable to verify. Roubaud has pointed out that the specimens of .4. maculipennis 

 from more northern latitudes are of greater size than those in more southern 

 countries. It seems therefore, that the secondary adaptation of the species to 

 animals in countries where domestic cattle are abundant, has produced a particular 

 race of mosquitoes, which is distinguished not only by its tastes and affinities but 

 also by it's greater size. 



Most probably Roubaud's indication is really quite right. In this connection 

 I take the liberty to call attention to the following fact. If we nowadays from our 

 country compare long series of .4. maculipennis with those of A. bifurcates there is 

 no doubt that the lirst named species is longer and larger than .4. bifurcatus. This 

 is also indicated by Theobald. According to him .4. maculipennis measures 6 to 

 7.5 mm. .4. bifurcatus 5 to 0V2 mm, with proboscis 8 — 8V2 mm. If we however take 

 the old descriptions by Zetterstedt and Meigen we shall find that the contrary is 

 the case; here .4. maculipennis is indicated as shorter than A. bifurcatus. Meigen 

 states (1818 p. 11) for A. maculipennis 3 lin. for .4. bifurcatus 3 1 /* lin. Zetterstedt 

 (1850 p. 3467) for A. maculipennis 2'/2 — 3 lin. for .4. bifurcatus 3 lin. Nowadays there 

 is not the slightest doubt about the fact that the common size of .4. maculalus in 

 our country is between 6.5 to 7.5 mm. and that the species is larger than .4. bifur- 

 catus. If the indications of the length of the two species by Meigen and Zetter- 

 stedt are really correct, it seems therefore that the average length of the 

 species has really increased in the course of the last century near the 

 northern limits of its area of distribution. This is only what we might 

 expect, according to Roubaud's and my own statements, Meigen and Zetterstedt 

 having measured the mosquitoes at a time when .4. maculipennis was no sedentary 

 stable mosquito but, as nowadays in the Mediterranean countries, a free flying 

 mosquito. 



Roubaud is inclined to regard the variations in the habits of .4. maculipennis 

 as "une evolution lente et durable des habitudes alimentaires d'Anophele c'esl-a-dire 

 dune evolution d'habitudes acquises ". I do not agree with Roubaud upon this 

 point. Firstly I wish to remind the reader of the fact that all mosquitoes have 

 unquestionably, from originally being flower visitors, in the course of time altered 

 their habits and, with regard to the female sex, are now in many species and genera 

 blood suckers. This biological variation is much greater than that which .4. maculi- 

 pennis has undergone with us. Further it must be remembered that .4. maculipennis 

 is by no means the only mosquito which has altered its habits over pari of its area 

 of distribution; the same is said to be the case with C. territans, which is a very 

 angry bloodsucker in America, but does not attack man in Central Europe (Schnei- 



D. K. I). Vidensk. Selsk. Ski\, nnturvldeiuk. og mi.th.m. Afcl. 8. Kjekke. VII, 1. 25 



