SURROUNDINGS OF GROWING INSECTS 229 



and fleshy but mottled with yellow, green, and brown ; its 

 body is compressed from above downwards, and it crawls 

 actively on its flat ventral surface, constantly rearing its 

 tapering front region into the air. 



The caterpillar of a moth may be regarded as a larva most 

 typically marked as vegetarian by its structure and habits, 

 yet there are several species of caterpillars that do not hesitate 

 to attack and devour other caterpillars, should the leafy food- 

 supply fail, and some species such as the noctuid Calymnia 

 trapezina habitually adopt this mode of feeding. They are 

 often described as " cannibals ", but this term of reproach 

 should be applied only when caterpillars eat members of their 

 own species, behaviour which appears to be unusual. The 



FIG. 115. MAGGOT OF HOVER-FLV (Syrphtis) (DORSAL VIEW). 



s/>, tail spiracles, x 3. 



larva of Calymnia and others that display these predaceous 

 habits do not differ in any structural feature from typical 

 leaf-eating caterpillars. The South European moth (Erastria 

 scitula} (Fig. 116 /), has, however, a caterpillar structurally 

 modified in accordance with a specialized carnivorous habit. 1 

 It feeds on scale-insects, biting its way through the scale of a 

 large female Lecanium and devouring the occupant, after 

 which it adopts the scale as a covering for itself. In keeping 

 with this habit, the caterpillar's body is short and egg-shaped 

 with its tail-region upturned (Fig. 116 a b c), so that the hind- 

 most prolegs are attached to the covering scale ; the prolegs 



1 C. V. Riley and L. O. Howard : " An Important Predatory Insect " 

 Insect Life, VI. 1894. 



