53 



remarkably high in the interior part; with two strong spines before collar; a row 

 of rather short cilia from collar, and about eight to ten rather feeble spines from 

 the inner edge; dentition: four, strong spines; before them a long dagger-like thorn ; 

 hairs below, process distinctly divided, with hairs on both apices ; a group of hairs 

 at base. Maxillae almost undivided at the apex, a rather long tuft of hairs and, at 

 its base, one spine. The whole space between suture and inner border covered 

 with long soft hairs and long bristles along the inner border; between suture and 

 palpe an area covered with soft hairs. Palpe well developed, short w r ith four digits. 

 Mentum triangular, an indistinct median tooth and from ten to twelve lateral thorns. 



Systematical remarks: 0. annulipes has always been a very disputed spe- 

 cies. Described by MEIGEN it has later been found in Austria, Germany, Russia, 

 Sweden, Holland, England; THEOBALD was not able to find it in England but later 

 on EDWARDS has described it from there. STAEGER like many others regarded it as 

 a variety of 0. cantons; differences in the male genitalia and in the structure of 

 the larva makes this supposition untenable. It may be mentioned that the STAGERS 

 specimens, now in the Royal Museum at Copenhagen, have been reexamined by 

 EDWARDS and myself; they are unquestionably 0. excrusians ; this may probably be 

 so in many other cases. 



Biology. I have only found this disputed species in various localities near 

 Arrese in North Seeland. My material was never good and not large enough for 

 me to make a more thorough study of the biology. 



It is quite in accordance with my own experience when LANG (1920 p. 88) 

 maintains that the larvae of 0. cantans are to be found in shaded pools of thick 

 woods, those of 0. annulipes in open pools. 



Geographical distribution: See under 0. cantans. 



5. O. vexans (Meigen). 



It is only with the greatest hesitation that I include this species among the 

 Danish Culicidse. STAEGER (1838 p. 554) mentions it and indicates that the species 

 is to be found in the forests, and that it is rather rare. 



Most probably STAEGER has only been able to distinguish it from 0. cantans 

 by means of its smaller size and very narrow white bands upon the tarsi. Speci- 

 mens of this kind I have also found in our forests; a little pond near Tjustruplake 

 was regularly visited for more than two years, more especially because I thought 

 that this pond contained what I supposed was the true 0. vexans ; the specimens 

 which where hatched in July were very small, only five or six mm. and the legs 

 were narrow banded. I have never seen the male; as the claspers are forked, the 

 species is, in the male sex, easily distinguishable from all other Danish mosquitoes. 



According to EDWARDS (1912 p. 195) its occurrence has not hitherto been 

 demonstrated with certainty in England, but according to LANG (1920 p. 85) it has 

 now been found there but is rare. In Germany it seems to be common. In the 

 neighbourhood of Strassbourgh it is said to be one of the most troublesome mos- 



