INSECTS 367 



species. The mouth-parts are adapted for biting, and are built 

 on the same plan as in the Cockroach (see p. 345), but with many 

 differences in detail, as seen, for example, in the more complete 

 fusion which has taken place between the two second maxillae, and 

 in the fact that these jaws are much reduced. The life- history of 

 a beetle (figs. 216 and 217) exhibits a complete metamorphosis, 

 the larva being a grub possessed, in most cases, of three pairs 

 of legs corresponding with those of the adult, and becoming a 

 pupa differing from that of a moth or butterfly as regards the 

 limbs and wings, which form prominent projections instead of 

 being merely indicated beneath the continuous 

 horny covering. 



Only a few common species, representing 

 important families, can be mentioned here. 



Tiger-Beetles are very active, predaceous in- 

 sects, including somewhere about a thousand 

 species, and distributed generally throughout the 

 world, though most abundant in the tropics. A 

 common British form is the Green Tiger- Beetle 

 (Cicindela campestris) (fig. 2 1 8), common on sandy F J 2l8 ._ Green T * g er- 

 banks, and distinguished by the beautiful golden- ^ tle (Odndeia camp es - 

 green colour of its upper surface. The larva is 

 provided with enormous curved mandibles, and excavates a 

 vertical burrow in which it lies in wait for prey. 



Ground- Beetles are also predaceous, and even more widely 

 distributed than the Tiger- Beetles, though much more numerous, 

 there being some eleven thousand species. They are least 

 abundant in the tropics. A large and well-known British species, 

 the Violet Ground - Beetle (Carabus violaceus), so named on 

 account of the dark violet sheen exhibited by its upper surface, 

 is common in fields and gardens, and may also be found in houses, 

 where it preys upon cockroaches and crickets. 



Water-Beetles include ravenous forms which resemble ground- 

 beetles in many respects, but are adapted to an aquatic life. The 

 largest British form is the Great Water- Beetle (Dytiscus marginalis] 

 (fig. 219), and here may also be included the Whirligig Beetle 

 (Gyrinus natator], which almost everyone must have noticed 

 twirling round and round at the surface of the water in ponds 

 and ditches. 



Rove-Beetles, possessing broad heads, narrow 7 bodies, and short 



