Deronectea depiessus, Fah.^ and clegans, Panzer. 295 



about 400 feet above sea-lovel, and within 2 njilos of the 

 main road between Carlisle and Neweastle, so that it was not 

 ditlicult to get at. The day of my visit was not propitious; 

 it began to rain heavily juat as 1 got to the tarn, and I spent 

 a miserable fifteen minutes paddling about at the edge, 

 during which time I cylleotcil five species of Ilydradcphaga, 

 and among the few specimens were two of Bold's " large aud 

 dark elejansy 



On an examination of these a few days later, and on com- 

 parison with some freshly caught specimens from the Nitli 

 at Dumfiies, 1 began to suspect that the Talkin Tarn indi- 

 vitluals were the *' de/tressus" reftrrod to by Ste. Clair 

 Deville, and I returned to the tain and collected a number of 

 specimens for turther examination. 



During August I examined a number of lochs and streams 

 in the south of Scotland (kSelkirk, Dumfries, Kirkcudbright, 

 and Ayr), and definitely came to the conclusion that there 

 were two sptcies ; but I was also gieatly struck by the».'xtia- 

 ordinary distribution of the rarer one, which occurred in only 

 a tow lochs scattered about the district. 8horlly after that, 

 militaiy duties, illness, and a long convalescence intervened, 

 and it is only recently that I have again taken up the matter, 

 and during August of last year 1 explored a number of 

 the Galloway lochs with a view to turther investigating 

 the distribution there of tho form which I take to be the 

 depressxis of Fabricius. 



The characters upon which the two species can be separated 

 arc three in number : (1) the shape of the thorax in ^ and 

 ? , (2) the form of the anterior tarsal claws of the ^ , and 

 (o) the form of the rcdeagu^. 



In geneial appearance the two species are usually very 

 much alike, tho coioui-plan being similar, but, as a rule, the 

 noithern species is rather larger than the other. The range 

 of colour-tone in the common species is greater than in tho 

 northern one, which is always dark, the yellow being reduced 

 to a minimum, the black always occupying a large extent of 

 the surface of the elytra. In the common species, especially 

 in specimens from the south, the yellow is usually lighter in 

 tone and liie black more limited, but the relationship between 

 the black and yellow seems to be related to habitat and to 

 climatic conditions, as is the case with Platambus maculatus, 

 Deronectes ai iseo-slriatiis^ and some otlier llydrarlephaga. 

 In the Seoltish h)chs I can find no dift'erenee whatever 

 in Colour-tune between the two species. 



20* 



