134 ZOOLOGY. 



leave it to die, and surround themselves with a 

 cocoon close to its dead body. There are, besides, 

 a few small and also some large ichneumon flies 

 which lay their eggs in the pupse of the cabbage 

 white, so that, e.g., in winter many of its angular pupse, 

 occurring on tree-stems and hedges, are found with 

 many small or several large white ichneumon larvse 

 within them. 



Family : Tenthredinidae {Saw-flies). 



Body thick-set. Abdomen never very long, and 

 united by a broad base to the thorax (Fig. 91). Saw- 

 shaped ovipositor (p. 89), drawn in when not in use, 

 and only protruded during egg-laying. Mandibles 

 strong, the remaining mouth-parts not so well de- 

 veloped. The larvse are false caterpillars (p. 92) ; 

 they can usually be recognized by their characteristic 

 attitude, for many of them bend the abdomen very 

 much upwards and forwards, especially when 

 frightened, and when at rest the hinder part of the 

 body is spirally coiled (Fig. 91). The fulJy developed 

 larva spins a cocoon in which it still remains for a 

 long time in the larval condition, even during the 

 whole winter. It becomes a pupa two or three weeks 

 before the appearance of the perfect insect. There 

 are many larvse of this kind destructive to woods, 

 but only a few which interest the farmer. Here is 

 included — 



The Turnip Saw-fly {Athalia spinarwm). 



Adult : Female one-third of an inch long, stretch 

 of wing over two-thirds of an inch ; male somewhat 

 smaller. Bright orange or reddish yellow. Head 

 black, thorax and legs with black markings. Wings 

 large. Larva: Length may be rather more than 

 two-thirds of an inch. The just-hatched larvse are 

 almost colourless, but the skin quickly becomes bright 



