198 THE BRITISH NATURE BOOK 



Colymbetes fuscus. The only British species, f inch long ; found in water ; 

 head black, tinged in front with red ; thorax and elytra tawny brown, 

 with yellowish edges ; red antennae ; black and red parti-coloured legs. 



Dytiscus. This genus contains some of the largest British Water Beetles, 

 and these may easily be kept in aquaria, provided that the top is covered ; 

 but remember that they are very voracious, and will attack all small fish and 

 other living creatures in the aquarium. The perfect insect lives for several 

 years, and in a state of nature frequently leaves the water for a flight, gener- 

 ally in the evening. The hind-legs are fringed with hairs, and are used as 

 oars. The fore-legs of the male have a remarkable disc on the tarsus, which 

 acts as a sucker, and is used to hold the female. It exudes some kind of 

 sticky fluid, for it will be noticed that the male often gets entangled by its 

 means in water-weed, and has to struggle to break away. 



This beetle has an additional protection from its enemies in the form of 

 an evil-smelling fluid, which it can eject from the thorax, and which is much 

 disliked by birds. The female places her eggs in slits in the stems of rushes 

 and other water plants. The larva hatches in three weeks, and soon grows, 

 feeding on other small water creatures. It is most rapacious, and a vigorous 

 swimmer, rising frequently to take in a supply of air from the surface of the 

 water by means of a pair of spiracles at the tail. It has twelve eyes, and a 

 cruel mouth and jaws. After moulting several times, it leaves the water, 

 and buries itself in the damp earth by the water-side to pupate. In this 

 condition it remains through the winter, emerging as a perfect beetle in the 

 spring. 



D. punctulatus (male) (Fig. 506). Note the discs on the fore-legs. Elytra 

 black, shaded with yellow at the sides ; antennae red ; legs dark brown. 

 Fairly common. 



D. marginalis. Is larger, the thorax having a complete yellow edge all 

 round. Very common. 



Acilius sulcatus (male) (Fig. 51). Note the discs on the fore-legs. Brown, 

 with two black bands on the thorax. Common in ponds and ditches. 



Haliplus fiavicollis (Fig. 42). Belonging to a genus of very small oval 

 beetles ; pale yellowish brown. Found in stagnant water. 



Hyphydrus ovatus (Fig. 43). Black, with a dull red tinge; almost round 

 in shape. Common in pools. 



Hydroporus planus (Fig. 44). Black, with reddish brown head and legs. 



H. palustris (Fig. 45). This very small species looks black to the naked 

 eye, but the magnifier shows it to be shaded with yellow, and to have two 

 yellow or tawny patches on the elytra. Common in water. 



Lacophilus minutus (Fig. 46). Dark olive-brown, a very active species. 

 Swims near the bottom of ponds. 



