34 BEETLES. 



Family IV. GYRINID^ (Whirligig Beetles). 



These are smaller species than those of the last family. 



They are shiny beetles, and are remarkable for having the eyes 



completely divided in the middle, as if they had four eyes. 



The antennffi have a large basal joint, and the remaining joints 



have the form of a small fusiform club. It is a small family, 



and only six species (which are not easy to identify) are found 



in Britain. 



Genus Gyrinus, Linn. 



Wing-cases punctate-striate. They are found gregariously 

 in standing or slowly flowing water, where they describe circles 

 on the surface. They have an air-bladder at the end of the 

 abdomen, and are good divers. 



* G. natator^ Fabr. (Plate IV., Fig. 14). This is bronze 

 colour beneath. The legs are reddish-brown. It is a common 

 species. 



Genus Orectochilus, Lacord. 



Wing-cases not punctate-striate. They live only in running 

 water, partly under stones and water-weeds, and partly on 

 the surface. 



* 0. villosKs, Fabr. (Plate IV., Fig. 15). The only British 

 species. It is elongated, convex, with a green shine on the 

 upper surface. It is rusty-red beneath. It hides in the 

 daytime, and swims about at night. 



Family V. HYDROPHILIDJE. 



Body oval, or nearly round. Antennae very short, not longer 

 than the head, and terminating in a club. The hind legs are 

 broadly flattened, and ciliated. They live in standing water, 

 and swim by moving the legs alternately, and not like oars, 



