INTRODUCTION. XXV 



pubescence ; but in some cases they are furnished with rigid 

 hairs and numerous long spines. These hairs are sometimes 

 simple, but more commonly they have a series of small 

 pointed pieces springing from each side, like leaves from a 

 stem. They are seldom placed irregularly over the surface of 

 the skin, but usually issue from a tubercle, and diverge in all 

 directions. These tubercular elevations vary greatly in number, 

 and are placed in a row across the middle of the segments. 

 The spinous caterpillars indigenous to Britain are but little 

 remarkable when compared with many exotic species ; but we 

 have several which afford good examples of this description of 

 defensive armour, such, for instance, as the 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 tip into several small 

 branches. Even when so numerous as entirely to cover the 

 body, they are not placed promiscuously, but arranged like the 

 tubercles formerly mentioned, in a certain order. Each seg- 

 ment, with the frequent exception of that next the head, is 

 armed with a transverse series, varying in number from four 

 to eight. The accompanying figure represents a magnified 

 section of the caterpillar of \Pyrameis\ cardui, exhibiting the 

 number, mode of arrangement, and structure of the spines 

 (Plate II., fig. 5). These appendages in many foreign cater- 

 pillars 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 for- 

 midable enemies." (Duncan.) 



The sole business of insects during the larval stage of their 



* Few birds prey upon hairy caterpillars, although the Cuckoo, which is 

 extremely fond of the larvoe of the Tiger Moth, Hypercompa caia, Linn. 

 (called, par excellence, the hairy-worm, or more frequently, the Woolly 

 pear), forms an exception to the rule, 



