32 BEETLES. 



of a blackish-brown colour. The raised borders of the wino"- 

 cases and the legs are reddish-brown. It also is common. 



* A. maculatus, Linn., is 8 mm. in length. It is oval, with 

 the elytra yellow, spotted with brown, and rusty-red legs. It 

 is common everywhere in running streams. 



Genus Cybistee, Curtis (Trogus, Leach). 

 Body broad, irregularly oval. The appendage of the proster- 

 num is pointed behind. The front legs of the males are 

 expanded and flattened. They live in stagnant water. 



C. Boeselii, Bergst. (Plate IV., Fig. 7). Pronotum and wing- 

 cases smooth in the male, finely ribbed in the female. It is 

 common in large fish-ponds on the Continent, but does not 

 appear to be indigenous to Britain. 



Genus Dytiscus, Linn. (True Water Beetles). 

 Elongated oval, slightly convex. The front tarsi are 

 expanded in the males into a rounded plate. The elytra 

 are generally ridged in the females. They frequent standing 

 water. 



* D. marginalis, Linn. (Plate IV., Fig. 8, male ; Fig. 9, 

 female). The appendage of the prosternum is bluntly pointed. 

 It is common in ponds and stagnant water. 



I), latissimus, Linn. (Plate IV., Fig. 10). Elytra with very 

 broad lateral borders. This large beetle, wliicli attains a length 

 of nearly 4 cm., is found only in lakes on the Continent ; it is 

 not British. 



* D. circumcindus, Ahrens (Plate IV, Fig. 11). This is 

 similar to the last species, but smaller. The process of the 

 metasternum is narrow and pointed. It lives in fish-ponds. 



* D. circumjlcxus, Fabr., is similar, but the female has 



