0)1 Aquatic Carnivorous Coleoptera or DytiscidcB. 249 



the Dytiscidse with five -jointed front feet are very interesting : in some of the 

 Agabini tlie male front feet difter but little from those of the female, being always 

 however something larger and more powerful owing to an increase in the bulk of 

 the three basal joints, which moreover bear beneath a peculiar pubescence, having 

 a sugary or glandular ajDpearance owing to the extremities of the hairs being 

 peculiarly formed. In the Colymbetini there is usually a superior development of 

 the male front feet to what we find in the Agabini ; the basal joints being more 

 dilated and some at any rate of the hairs on their under surface furnished with hairs 

 bearing paper-like expansions or cups, sometimes arranged in transverse series 

 (Colymbetes). It is however in the Dytlscini, Hydaticides, and Cybistrini, that 

 we find a truly wonderful development of the male tarsi ; in these groups, the 

 three basal joints are not only enormously dilated, but are also accurately co-adapted 

 with one another, so as to form a large circular (or transversely elliptical in Cy bister) 

 disc or plate, the under surface of which bears larger or smaller stalked cups or 

 palettes, and sometimes also fine pubescence, while the edges of the plate are 

 regularly fringed with spines or densely placed fringing hairs. The hio-hest 

 development is found in Dytiscus, Acihus, Cybister and Megadytes, where 

 there are present on the under surface both fine hairs and very highly developed 

 palettes. These remarkably constructed feet are powerful organs of adhesion to 

 smooth surfaces and I believe also are highly developed sensitive organs. 



The claws of the front feet vary much, they are usually little developed in the 

 Hydroporides, and are very delicate in Hyphydrus ; in the Macro-Dytiscidse on the 

 other hand the front claws are always large, and are frequently remarkably 

 constructed in the males, especially in the tribe Colymbetides. 



Deformity of the dilated tarsi of the males seems to be of frequent occurrence, 

 I have observed it in several species of such different genera as Deronectes, Ao-abus, 

 and Dytiscus. 



The Middle Legs are usually similar to, or differ comparatively slightly from the 

 front ones, but their coxee are generally shorter and less conical, and the peculiar 

 developments in the male sex are much less extraordinary. The coxse are usually 

 deeply embedded in their cavities, and are then always nearly globose, and this is 

 invariably the case when they are well separated from one another ; when however 

 they are nearly contiguous they become more or less elongate and conical, and project 

 from their cavities, as is especially the case in the Vatellini and Sternopriscus. The 

 tx'ochanters and femora are very similar to those of the front legs, but nre not the 

 seat of such great modifications in the male sex. The tibiae too are usually similar to 

 the front ones, but often are slightly more slender and elongate ; their outer edo-e 

 is always set with long cilise, and the front face in the Macro-Dytiscidte is nearly 

 always roughened by bearing longer or shorter spines, the apex is always furnished 

 with two spurs placed near one another at the inner margin : the extremity of the 

 tibia is truncate nearly at right angles to its axis, and the edges of the truncature 



