62 NATURAL ARRANGEMENT OF INSECTS. 



hinder extremity of the body is invariably narrow and 

 pointed. These peculiarities are the very reverse of 

 those of the larvae belonging to the last type, and 

 render this of very easy detection. It might be in- 

 ferred from the term vermiform, that these larvse are 

 always of the lengthened shape of a worm, and that in 

 the mode of taking their food they are suctorial ; but 

 neither of these inferences would be correct. These 

 caterpillars are likened to the true earth-worms, because 

 both their extremities are pointed, and because they are 

 the representatives of those creatures among the diurnal 

 Lepidoptera. Again, they are termed suctorial, because 

 most of their corresponding types or representatives 

 among other animals derive their food from suction 

 alone, and are the most toothless of their respective 

 groups. The different shapes which belong to the suc- 

 torial type among the diurnal butterflies, is the onisci- 

 form, or chclonian : in other words, its shape is inter- 

 mediate between that of a wood-louse {Oniscus Lin.) 

 and a chelonian reptile, or tortoise : the head and tail, 

 indeed, are small and narrow ; but the body is dispro- 

 portionably broad, much depressed, and appears as if 

 divided into plates like the shell on the back of a 

 tortoise. Most of the butterflies belonging to this type 

 are natives of the Tropics ; but there is one division 

 which is more particularly European, and which con- 

 stitutes the genus Polyommatus* , or, the Blues and 

 Coppers, of English collectors. 



(59.) The Rasorial, or Thysanuriform, caterpillars 

 belong to the last type we have to notice ; and they 

 differ, in many striking peculiarities, from all that we 

 have yet spoken of. In the general shape of their body, 

 and in the proportionate size of their head, they as- 

 similate to the iuliform and the raptorial types ; but 

 from both these they may be known by two characters. 

 Either the head itself is armed with distinct spines, 

 forming a sort of crest round the back part ; or it seems 

 divided into two parts by a deep notch, each portion 



• Zool. 111. ii. pL m. 



