526 WATER BEETLES. 
WE now come to the large group of WATER BEETLES, which are divided 
into several families. ; ; 
In order to enable them to perform the various movements which are 
necessary for their aquatic existence, their hind legs are developed into oars 
with flattened blades and stiff hairy fringes, and the mode of respiration is 
slightly altered in order to accommodate itself to the surrounding conditions, 
It has been already mentioned that in all insects the respiration is conducted 
through a series of apertures set along the sides, and technically called 
spiracles. In the Water Beetles, the spiracles are set rather high, so as to be 
covered by the hollowed elytra, and to be capable of breathing the air under 
those organs. When, therefore, the beetle dives it is in no ways. distressed 
for want of air, as it carries a tolerable-supply beneath the ‘elytra. When, 
however, that supply is exhausted, the beetle rises to the suriace, just pushes 
the ends of the elytra out of the water, takes in a fresh supply of air, and 
again seeks its subaquatic haunts. : ; : oe 
The male of the Great Water Beetle, in comimon with other species, is 
(Llybius ater.) WALER BEETLES, (Dyticus dimidiatus.) 
specially notable for the singular development of the fore-legs, the tarsi of 
which are developed in a most extraordinary apparatus caused by the dilata- 
tion of the three first joints. which are flattened so as to form a nearly circular 
disc, covered on its under surface with a multitude of wonderfully-constructed 
suckers, one being very large, another about half its size, and the others very 
small, and set on pear-shaped footstalks. 
The larger specimen in the engraving is the Dydicus dimidiatus, and the 
smaller is the //ydius ater, both British species. 
PASSING by several large and interesting families, we come to the curious 
creatures which will at once be recognised by reference to the illustration. 
These beetles are popularly known by the name of ROVE BEETLES, or 
COCKTAILS, the latter name being given to them on account of their habit of 
curling up the abdomen when they are alarmed or irritated. The common 
BLACK COCKTAIL has, when it assumes this attitude, standing its ground 
defiantly with open jaws and elevated tail, so diabolical an aspect that the 
