298 Caph F. BalCour-Browne on 



■width in botli species, but until I examined the Locli 

 Dunjioon specimens there was always a wide gap between 

 the two types of aideagus, the northern form being rounded 

 at or even slightly flattened across the apex, and the common 

 form pointed; and here, in specimens from this one loch, I 

 found intermediates closing the gap. Ln the tarsal claw- 

 character the males are mostly of the northern type, but in 

 the shape of the thorax there is considerable variation. The 

 females, too, are mostly what, in the absence of males, I 

 should have left unnamed or put down very doubtfully as the 

 common species. 



The first explanation which will occur to anyone is that we 

 have in Loch Dungeon a hybrid ; but there are one or two 

 objections to this view. In the first place, I did not find in 

 the loch any male with an fedeagus of the normal " common 

 species " ty})e. The narrowest jedeagus is as broad as or 

 broader than the broadest pedeagus of the common species 

 {v. fig. 10), although the surrounding lochs contain the 

 common species with a narrower sedeagns. 



In the second place, if this loch contains hybrids, why does 

 no other of the thirty-two lochs I have examined contain 

 them?* With one exception I have not found both species 

 present together in any loch, and in the exceptional case — 

 Loch Stroan — I only found a single male of the northern 

 species, while the common one was abundant there. 



It seems open to question, therefore, whether we have 

 merely one species showing extreme range of form or whether 

 we have two species very closely related to one another. On 

 the evidence in ni}'- possession, i. e., after examining con- 

 siderably more than five hundred specimens, I am inclined 

 to adopt the latter view, first, because the variation in the 

 rcdeagus does not overlap in the two forms, and connecting- 

 links have so far only turned up in the one loch, and, secondly, 

 because of the extraordinary distribution, isolation, and rarity 

 of this northern one, to which I will refer in detail later on. 



Having come to the conclusion that these are two distinct 

 species, the question arises, are they, as has been suggested, 

 the depressus of Fabricius and the elegans of Panzer, or is one 

 of them something new? The most direct method of settling 

 the question would have been by comparison with the types 

 of the two species, and I had great hopes that the " depressus " 



* I have altogether examined forty-five lochs in southern Scotland, 

 but seventeen of these contained neither species. 



