these pools by means of dikes, which preserve the low-lying island from inunda- 

 tions, we find hundreds of freshwater pools all over the meadows, more especially 

 in spring, in which 0. commnnis are hatched in early spring, and later on 0. lutes- 

 cens; I have only taken the larva of lutescens in one single brackish pool and 

 only one specimen; it seems as if the above-named dikes form a very conspicuous 

 barrier between 0. curriei and 0. caspius on one side and 0. lutescens on the other. 

 Later on, as imagines, they have the same flying areas. 



From these observations we are able to state that the home of 0. lutescens 

 seems to be the open meadows bordering on lakes and sea-shores; they do not dwell 

 in forests, the outskirts of which is the natural home of 0. excrucians, only on 

 very warm days do they now and then seek them. There is unquestionably regu- 

 larly only one single generation, hatched in the latter part of May and on the wing 

 the whole summer, attacking cattle and horses more than men. Curiously enough, 

 this species, which has not hitherto been described in our country, is perhaps the 

 one which forms the greatest swarms, standing in clouds over the meadows; the 

 males disappear before the last part of June, and the females begin to throw their 

 numerous single eggs over the vast plains, then dry, but inundated before January, 

 at all events in the following spring. 



Geographical distribution: England, Germany, Russia, and Scandinavia; 

 it is identic with 0. fletcheri Coq, hitherto found in North America. H. D. K. (1917 

 p. 678) indicate Prairies of western Canada and north western United States. 



Systematical remarks with regard to the four last-named 'species. 

 In the above-named localities I found, in 1917 1919, the larvae of the now men- 

 tioned three species O. lutescens, excrucians and annulipes; these larvae were at that 

 time unknown. By means of the remarkably long siphO and short antennae I was 

 always able to distinguish the larvae of these three species from those of cantans, 

 communis and Theobaldia morsitans-, I first regarded the three larvae as belonging 

 to the same species. A closer examination showed that, between these long siphoed 

 larvae there were slight, but conspicuous, differences; later on I therefore regarded 

 them as belonging to different species, and made drawings of them. As the ima- 

 gines appeared, I immediately saw that I had at all events two species before me; 

 regarding those from the small ponds at Hillerad as differing from those from the 

 meadows near Arres0 and Tjustrupso. Later on I was inclined to regard some of 

 the material from the ponds in North Seeland as belonging to two different species, 

 one being 0. annulipes; if this was right, however, I was unable to distinguish this 

 species from 0. cantans, taking an intermediate position between 0. cantans and 

 0. excrucians. - - Later on, when in July August I examined the same localities, 

 where I had gathered the larvae in spring, and from which I had hatched the pre- 

 sumed three species in the latter part of May, the case was much more trouble- 

 some. The males had disappeared; at that time we find only females in all the 

 above-named localities. When the lust of blood of this sex has been satisfied, 



I). K. D. Vidensk. Selsk. Skr, naturvidensk. otf mathem. Aid. 8. R.-ekke, VII, 1. 9 



