INSECTA: COLEOPTERA 



245 



The Head. 



Respiration. 



the male in holding the female. The corresponding joints 

 on the second pair of legs in the male are also slightly 

 enlarged and capable of some adhesion. The back legs in 

 both sexes are strongly feathered, and are the chief organs 

 of locomotion. 



The head bears compound eyes, which project 



but little, and a pair of long, delicate, jointed 

 antennae. From the sides of the mouth are seen projecting two 

 pairs of palps, and strong toothed mandibles are also present. 

 As has been mentioned above, the beetle always 

 ■ comes to the surface to renew its air supply. There 

 is a space between the wing-covers and the abdomen, and 

 this space is always filled with 

 air, and into it, on each side, 

 open eight spiracles, of which 

 the last pair is specially large. 

 When the beetle pushes its 

 tail out of the water, air is 

 taken in by these two last 

 spiracles, and also the large 

 air- bubble below the elytra 

 is renewed; thus a store of 

 air is obtained for use when 

 the beetle is swimming below 

 the surface. The silvery 

 bubble of air is often to be 

 seen extending backwards 

 beyond the elytra. Although 



Dyticus spends most of its life in the water, it will occasion- 

 ally fly, especially at night, and so it gets widely distributed. 

 On the ground it is very awkward and helpless, jerking about 

 in a very unsteady fashion. 



In the spring, the female beetle lays her eggs, 

 tion"°' iiis^i"*'i''ig them in a slit which she makes in the 



stem of some water plant (Fig. 172). The yellow- 

 brown larvae hatch in about three weeks, and are full grown in 

 another four or five weeks — an unusually rapid development. 

 The larvae of Dyticus are very common in ponds 

 ' and ditches. They are the very fierce, active 

 little creatures known to children as " toe-nippers." They kill 

 and suck the blood of a very large number of other soft-bodied 



Fig. 171. — Dyticus marginalis. 



Wing-cover and one wing pulled aside to 

 show the eight spiracles down the 

 right side of the body. 



