Change of Diet 



larva reared on vegetable food refuses in 

 any Way to lend itself to a change of diet. 

 However pressed by hunger, the caterpillar 

 of the Spurge Hawk-moth, which browses 

 on the tithymals, will allow itself to starve 

 in front of a cabbage leaf which makes a 

 peerless meal for the Pieris. Its stomach, 

 burned by pungent spices, will find the Cru- 

 cifera insipid and uneatable, though its 

 piquancy is enhanced by essence of sulphur. 

 The Pieris, on its part, takes good care not 

 to touch the tithymals: they would endanger 

 its life. The caterpillar of the Death's- 

 head Hawk-moth requires the solanaceous 

 narcotics, principally the potato, and will 

 have nothing else. All that is not seasoned 

 with solanin it abhors. And it is not only 

 larvae whose food is strongly spiced with 

 alkaloids and other poisonous substances that 

 refuse any innovation in their food; the 

 others, even those whose diet is least juicy, 

 are invincibly uncompromising. Each has 

 its plant or its group of plants, beyond which 

 nothing is acceptable. 



I remember a late frost which had nipped 

 the buds of the mulberry-trees during the 

 night, just when the first leaves were out. 

 Next day there was great excitement among 

 my neighbours: the Silk-worms had hatched 

 187 



