■WATBE-BEETLBS. 213 



elytra, and so making a curious noise, it has received the 

 names of the " Squeaker," the " Screech Beetle," and the 

 " Chirping Beetle." Its body appears more fitted for moving 

 upon the land than through the water. It is, however, very 

 convex, and is able, with an ambulatory motion, to swim fairly 

 weU. It does not seem to be a great eater, and I have never 

 seen it attempt to attack a fish or any other of its com- 

 panions. This beetle, and many others, are fond of hiding 

 themselves in the gravel of the aquarium, only leaving exposed 

 the bubbles of air which are attached to the apices of their 

 elytra. P. Hermanni is so convex that when it is taken out 

 of the water it can hardly move at all. It is never a very 

 active- insect. Its colour is a dull red. A patch round the 

 eyes, the exterior and posterior margins of the thorax, and a 

 very large spot on the elytra, are black. It is also a dull red 

 underneath its body, except the breast and the apex of the 

 abdomen, which are black. This insect is about ^in. long, 

 and is fairly abundant in the weedy ditches and ponds of 

 many parts of England, but especially in the neighbourhood 

 of London. 



The sub-family Haliplides possesses two genera — Haliplus 

 and Cnemidotus. The Haliplides have more the appearance 

 of ten-estrial beetles than aquatic, their legs not being very 

 weU adapted for swimming, and their heads are more promi- 

 nent than those of most of their relatives. They swim 

 with Em ambulatory motion, although not very often, as they 

 spend a considerable portion of their time in crawling upon 

 the water-plants. They are broad and convex in shape, and 

 are hardly ever more than ^in. in length, but often less. 

 Their elytra, which are generally of a yellowish colour, have 

 large punctures. Their antennsB are ten-jointed, while those 

 the rest of the Bytiscidce are eleven- jointed. In distinguish- 

 ing one species from another, one should be guided more by 

 the shape of the beetle and the punctures upon its wing-cases 

 than by its size and colour. 



The genus Haliplus contains eleven species, the commonest 

 perhaps of which is H. ruficoUis. This is a very small beetle, 

 less than iin. in length, and abounds almost everywhere. It 



