534 On Aquatic Carnivorous Coleoptera or Dytiscide. 
of the male, while the females before me from Lago Pinter, seven in number are 
all similar to the males. There thus appear to be two Alpine races, the males of 
the two being similar while the females are very different. The species however 
not only varies in sculpture both absolutely (that is in both sexes considered together) 
and sexually, but it shows quite as great and even more interesting modifications, 
in what may be called quite structural characters; thus the shape becomes in the 
Alpine forms very different from what obtains in the plains, and in correspondence 
with this modification of shape is a change in the legs, which are very much more 
elongate and slender, (that is less highty developed for swimming) than they are 
in the individuals of the plain; this diminution in the power of the legs reaches its 
extreme in the most divergent females of both the Alpine forms. 
The male tarsi are subject also to much variation, the amount of their incrassation 
and the sexual structure of the front claws being each inconstant; the greatest 
development of the male feet and claws is found in the large individuals of the 
plains, the smallest in the Alpine forms ; in these latter the amount of dilatation of 
the tarsus is greatly diminished, and the posterior of the claws on the front feet 
becomes more slender, the dilatation of its hinder edge being in extreme cases very 
greatly diminished : the front claws moreover are variable independently of Alpine 
or boreal localization, for I have a male (from Corsica?) in which the anterior claw 
retains pretty nearly the normal shape, but is not longer than the front one. 
It seems very difficult to comprehend these variations. Especially peculiar seems 
the fact that the males of Alpine and boreal districts depart from the dwellers of 
the plains in one direction only, and yet their females depart in two opposite 
directions ; equally difficult of explanation is the fact that though disparity in 
sculpture of the sexes is the rule, yet this disparity disappears in the two forms 
which in other respects are most widely different from one another, viz., the large 
and powerful South European variety, and the feeble, monomorphic Alpine variety: 
we seem however at any rate justified in inferring that the peculiar sculpture of the 
females bears no correlation to the development of the male tarsi. 
Group 21. 
Anterior portion of prosternum united with prosternal process so as to form a 
sensible angie ; prosternal process compressed ; wings of metasternum rather short ; 
coxal lines not greatly turned outwards at the extremity; coxal border small; 
male anterior tarsi much developed ; hind legs slender. 
Two Palearctic species. 
