342 Orthorrhapha brachycera. 



not long, the femora somewhat, more or less, thickened in the basal 

 part, and femora and tibiæ are armed with spines below; these 

 spines show generally sexual characters, they are sometimes most 

 numerous in the female, sometimes on the contrary only present in 

 the male, and again in other cases equal in both sexes; the posterlor 

 legs are long and slender; the hind metatarsus considerably longer 

 than the second joint, without bristles. The hind coxæ have no 

 bristles on the outer side; the posterior legs have scattered bristles, 

 but the hind femora no special preapical bristles; the tibiæ have 

 (generally) only small apical bristles. There are two claws, two well 

 developed pulvilli, and a large and well developed, more or less pul- 

 villiform empodium, which is sometimes narrower^ sometimes as broad 

 as or almost as broad as the pulvilli. Wings somewhat long and nar- 

 row, sometimes more or less spotted; the me.diastinal vein somewhat 

 elongated, not terminating in the subcostal vein; the last part of the 

 discai vein a little curved or undulated, and slightly converging to- 

 wards the cubital vein; posterior cross-vein placed after the middle, 

 the last part of the postical vein not longer than the cross-vein ; anal 

 vein short. Axillary lobe well developed. The discai vein with a 

 convexity. Squamulæ with the angulary lobe small, bearing a dense, 

 but not specially long fringe; the inner part of the squamulæ well 

 developed, with a fringe, which is nearly as long as that on the 

 angulary lobe. 



The developmental stages are not known, but once Mr. Kryger 

 and I have taken quite fresh and still white specimens of H. praecox 

 at the shore below sea-weed; it is thus probable that the larvæ and 

 pupæ live here, and I think the same is the case with regard to the 

 other species; the mentioned specimens were observed on ^/s. 



The species of Hydrophorus are characteristic by their some- 

 what duU colours, the raptorial front legs and long posterior legs, 

 and by their short shape. They occur all at water, some especially 

 at the shores, others at fresh water, and others again on both piaces; 

 most or all specimens are able to run on the surface of the water 

 with great ability. They show in exterior and partly in the behaviour 

 some resemblance to the species of Clinocera, and also to some 

 degree to some Ephydrids. 



Of the genus about 19 species are known from the palæarctic 

 region; 7 have hitherto been found in Denmark, 



Table of Species. 



1. Wings unspotted 2. 



— Wings with two or numerous spots 5. 



