WATEE-BEBTLES. 225 



thorax deeply punctured. The antennae, palpi, and legs are 

 dark brown. It is rather less than ^in. long. 



The beetles belonging to the genus Limnebius are the 

 tiniest of the SydropMUdce, some of them being less than 

 -^in. in length. Their bodies, which are black, are slightly 

 depressed. Their antennae are eight- jointed, the last six joints 

 forming the club. The elytra are slightly truncate at the 

 apex. These insects are divided into five species, some of 

 which are very common. 



The beetles comprised in the family Parnidce, though very 

 interesting, are not so suitable for the aquariunx as those 

 already mentioned, as they are generally found in swift- 

 running water. The insects of the sub-family Parnides are 

 covered with a kind of hair, by means of which they are 

 able to carry with them sufficient air for their wants during 

 the long time they are accustomed to spend beneath the 

 water. Parnus prolifericornis is the commonest species, and 

 is Jin. long. It is oblong in shape, and of a dark brown 

 colour, its legs being reddish. The Parnidce, as well as the 

 SydrophilidcB, are herbivorous. 



The Elmides, which are also a sub-family of the ParnidoB, 

 are chiefly remarkable for their largely- developed tarsi and 

 claws, by means of which they are able to cling to stones at 

 the bottom of very swift-running water. The longest feet 

 and claws are possessed by lAmnius tuherculatus, the one 

 species of the genus. This remarkable insect, which is rare 

 and local, is found in the River Trent. 



Very often an aquarium is found to be made out of pro- 

 portion — that is, its depth is too great for its length and 

 breadth. This mistake of construction can be rectified by 

 filling the vessel only half or three-quarters full, as the case 

 may be. Such a tank as this vrill be very useful for keeping 

 not only many of the smaller species of the Hyd/ropMlidcB, 

 but also some of the very beautiful and interesting beetles 

 which live rather upon aquatic plants than in the water itself, 

 such as certain of the Donaciadm, Chrysomelidce, and Galleru- 

 cidce, and even one or two of the Ehynchophora, or Weevils. 

 The tank for these insects should be covered with a sheet of 



