INTRODUCTION. 73 



row across the middle of tlie segments. The spi- 

 nous caterpillars indigenous to Britain are but little 

 remarkable when compared with many exotic spe- 

 cies, but we have several which afford good examples 

 of this description of defensive armour ; such, for 

 instance, as the very common kinds that feed on the 

 nettle. In these, and most other instances, the spines 

 are sufficiently strong and sharp as readily to pierce 

 the skin of the hand. They are very often beset with 

 hairs, and frequently divide towards the top into se- 

 veral small branches. Even when so numerous as 

 entirely to cover the body, they are not placed pro- 

 miscuously, but arranged, like the tubercles formerly 

 mentioned, in a certain order. Each segment, with 

 the frequent exception of that next the head, is arm- 

 ed with a transverse series, varying in number from 

 four to eight. The accompanying figure represents 

 a magnified section of the caterpillar of Cynthi 

 Cardui, exhibiting the number, mode of arrangement, 

 and structure of the spines. (Plate II. fig. 5 ) These 

 appendages, in many foreign caterpillars, are said to 

 sting like a nettle ; and there can be no doubt, that, 

 in all cases, they are a powerful means of defence, 

 not only against the smaller birds, * but even against 

 more formidable enemies. 



* Few birds prey upon hairy caterpillars, although the 

 Cuckoo which is extremely fond of the larvaj of Arctia caja 

 (called par excellence the hairy-ivorm) forms an exception 

 to the rule. 



