INSECTS 



371 



Fig. 224.— Turnip Saw-Fly {Atkalia spinamtm 

 I, Adult female, enlarged (natural size represented to left of it); 

 3, 2, Eggs (natural size and enlarged) ; 4, 5, 6, larvae ; 7, cocoon ; 

 8, pupa in cocoon. 



addition to the three pairs of legs proper, while a caterpillar never 

 has more than five pairs of pro-legs, and often fewer. Nor do 

 these pro-legs possess, like those of most caterpillars, a curved row 

 or circlet of minute bristles 

 near their tips. Further, a 

 "false" caterpillar has a 

 rounded instead of a flat- 

 tened head, moves its ab- 

 domen vertically up and 

 down when disturbed, and 

 curls it up in a state of rest. 



The "saw" of a saw-fly 

 consists of two curved saw- 

 like blades protected by 

 sheaths when not in use. 

 The blades are worked alter- 

 nately backwards and forwards, and the eggs slip down between 

 them into the incision formed. A common species is the Turnip 

 Saw-Fly {Atkalia spinarum) (fig. 224), the larvae of which ravage 

 the crop after which the insect 

 is named. 



In a Wood-Borer the blades 

 corresponding to the saws of a 

 saw-fly are fused together into 

 a boring spine, which is used 

 like an auger. A conspicuous 

 species, not infrequently seen 

 in this country, is the Large 

 Wood- Borer (Sirex gigas) (fig. 

 225), also called Wood- Wasp 

 from the transverse black and 

 yellow bandings of its body. 

 The female bores holes in pine-trees in which to lay her eggs, 

 and from these, eyeless grubs hatch out which only possess the 

 three pairs of ordinary legs. These larvae burrow in the timber 

 by means of their strong mandibles, and later on become pupae 

 enclosed in cocoons formed from silk mixed with fragments of 

 wood. 



2. The Insect- Eating Hymenoptera are so named because 

 the larvae are commonly parasitic within the larvae of other insects. 



Fig. 225. — Large Wood-Borer or Wood-Wasp {Sirex gigas) 



