150 Mv. J. W. Dunning on 



serve to distinguish latvpennis (Hansoni) from nivens 

 {Garnonsii) , but are common to both forms; the English 

 latipennis exhibits as great a range of variation, both in 

 size and colour, as the English niveus ; specimens from 

 Cheshunt are precisely like those sent by Staudinger, 

 and of the uniform dull tint depicted by Herrich-SchafFer, 

 whilst others from Hampstead are of lighter hue, and 

 prettily mottled, or flushed with deeper brown. The 

 important point is, undoubtedly, the broader rounder 

 wing of A. latipennis, and though the winged females 

 agree well with one another, from whatever locality they 

 come, there certainly is a difference in the shape of the 

 wings of the male, which is very pei-ceptible when the 

 narrowest and the broadest winged specimens are con- 

 trasted ; and some of the Hampstead examples are larger 

 insects, and have even broader wings than the Conti- 

 nental latipennis, differing in this respect as much from 

 latipennis as the latter does from niveus. But other males 

 captured at the same time and place, and specimens 

 taken elsewhere consorting with amply-winged females, 

 exhibit the narrower wing which is supposed to distin- 

 guish niveus ; and, in fact, there is every gradation, the 

 extremes may be connected by intermediate forms, and 

 I do not think the breadth of wing can be depended upon 

 as a test of their specific distinctness. 



If this be so, I submit that there is, after all, but one 

 species of Acentropus ; with a wide European range, and 

 exhibiting perhaps slight modifications in different loca- 

 lities, but gradual modifications, the extreme forms being 

 connected by intermediate links. Its geographical range 

 extends from about 4° W. to 45° E. longitude, and from 

 48° to 61° N. latitude; even thos-e who advocate the 

 sepai'ation into several species admit that A. Nevce ranges 

 from the Gulf of Bothnia to the Bodensee, whilst A. lati- 

 pennis occurs alike in England and South-Eastern Russia. 

 And indeed, with the exception of the isolated Sarepta, 

 on the Volga, there is a continuity about the localities 

 which favours the idea of the unity of the species ; thus 

 starting from St. Petersburg, we pass along the North 

 coast of the Gulf of Finland, then along the Prussian 

 shore of the Baltic, and inland to Frankfort-on-the-Oder, 

 then to Holland, England, France, and the southermost 

 part of Baden or the northern confines of Switzerland. 

 The insect is so insignificant in appearance that it may 

 well be overlooked ; if searched for, I have no doubt it 

 would be found wherever a pond-weed grows. 



