xv INSECTALEPIDOPTERA 223 



marked change in shape at this time. A resting period is 

 then necessary for the completion of the internal structure 

 and of the new mouth-parts which have now to be fitted for 

 sucking nectar from flowers. The biting mandibles of the 

 caterpillar are no longer needed and disappear altogether. 

 The change in diet is necessitated by the change in the mode 

 of life ; the active flying butterfly needs a lighter and more 

 nutritious diet than the slowly crawling caterpillar. 



The caterpillars of this butterfly are often very 

 common and very destructive, especially the very 

 numerous summer brood, which feeds almost 

 entirely on cabbage. The smaller spring brood is found on 

 various food plants, chiefly 



those of the cruciferous order. (\. 



The summer brood, however, 

 is very liable to the attack of 

 a four- winged hymenopterous 

 insect known as an "ichneumon 

 fly " (Apanteles (Microgaster) 

 glomeratus). This insect lays FIG. 152. Caterpillar of Pieris 

 its eggs inside the body of the brassicae attacked by the Ich- 

 caterpillar after piercing its neumon Fly ' 



i . .,i -, i ., B, Cocoons of larvae which have made 



Skin With Its Sharp OVlpOSltor. the irwayout f the body of the cater- 



The larvae Of the fly live pillar ; A, one ichneumon fly which 



parasitically inside the Cater- has emerged from one of the cocoons. 



pillar, until they are about to pupate, when they emerge in 

 numbers through the skin and pupate near it, surrounding 

 themselves with little yellow silk cocoons (Fig. 152, B). At 

 this point, the caterpillar usually dies, and much as we 

 may dislike the methods of the ichneumon fly, it doubtless 

 is of great use in preventing the Cabbage White Caterpillars 

 from becoming a serious plague. 



Pieridae Belonging to the same family of Butterflies as 

 the Large and Small Cabbage Whites, i.e. the family 

 of the Pieridae, are the Orange Tip and the Brimstone Butter- 

 flies. They all have the same habit of supporting the body, 

 by a silken girdle, when pupating. 



The Orange Tip spends nine or ten months of the year in 

 the pupal stage. The butterfly emerges in May, and lays its 

 eggs in June, on the flower-stalks of some cruciferous plant, 

 frequently cuckoo-flower or hedge -mustard. On this plant 



