WATBE-BEETLES. 



215 



which is a light rusty red, has the anterior and posterior 

 margins black. The elytra are black, and are covered with 

 reddish spots placed in threes. The legs and antennae are a 

 rusty red. This beetle is fairly common. M. palustris is a 

 small insect found in great abundance almost everywhere. It 

 is about ^in. in length. Its head, margins of thorax, and legs, 

 are red, and its elytra are dark brown, spotted with yellow. 

 This beetle, however, varies much in its colouring. S. rivalis 

 (as its specific names implies) is. found in streams, while most of 

 its relatives live in stagnant water. The colour of this very 

 pretty little insect is brownish-yellow, and the thorax has a 

 black line down the centre. There are two irregular black 



;-;^^''" '"■:P''^^ 





Fig. 137. a, Hyphydbds ovatus ; 6, Hydroporus 12-pustulatiis. 



patches upon the elytra, jointed together by three or four 

 lines of the same colour. This beetle, which is not ^in. in 

 length, is not very common. 



All the Hydroporides are small, and some of them are 

 very prettily marked. The males can often be distinguished 

 from the females by their shining appearance. 



The Gyrinidas, which includes the genera Gyrinus and 

 Orectochiliis, form the latter of the two families of the 

 Hydradephaga. 



Few water-beetles are more commonly known than the 

 merry and active little insects which belong to the genus 



