298 Capt. F. Balfour-Browne on 
width in both species, but until I examined the Loch 
Dungeon specimens there was always a wide gap between 
the two types of zedeagus, 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. In 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 edeagus of the normal “ common 
species’? type. The narrowest edeagus is as broad as or 
broader than the broadest eedeagus of the common species 
(v. fig. 10), although the surrounding lochs contain the 
common species with a narrower edeagus. 
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. 
Tt 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 my possession, i. ¢., after examining con- 
siderably more than five hundred specimens, I am inclined 
to adopt the latter view, first, because the variation in the 
eedeagus 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. 
