CHAPTER V 



Dyticus marginalia A WATER-BEETLE 



THE beetles, or Coleoptera, constitute the predominant order 

 of insects, there being about 150,000 known species, of which 

 about 3300 are British. The name of the order has reference 

 to the sheathing character of the front wings : for these organs, 

 known as elytra, are not used in flight, but serve solely as covers 

 for the hind- (flight) wings when these are folded and at rest. 

 In some species, however, the wings and elytra are so reduced 



A B 



FlG. 18. Adult Dyticus marginalis. A, male ; B, female. 



as to be useless, or, indeed, are entirely absent ; while in others 

 the elytra are fused together over the back so as to be incapable 

 of separation. The prothorax is far more freely movable upon 

 the mesothorax than is the case in other insects ; but the meso- 

 thorax is very small, while the metathorax, except in flightless 

 species, is largely developed. 



