OF INSECTS. 309 



more than sixteen feet, while the larvae of saw-flies 

 have generally from eighteen to twenty- two ; a few 

 have only six, a circumstance which again distin- 

 guishes them from true caterpillars, in which the 

 number of these parts is never below ten. Another 

 mark of distinction is afforded by the structure of 

 the feet. In lepidopterous larvae the abdominal legs 

 are surmounted by a coronet of small hooks, ap- 

 pendages which are never found in those of false 

 caterpillars, as the latter are simply mammiform 

 protuberances. This minute difference, which can 

 only be detected by the microscope, has however 

 a material influence over the habits of the respec- 

 tive caterpillars, which often enables us to distin- 

 guish them at first sight. The coronet of hooks 

 converts the membranous or abdominal legs of true 

 caterpillars into efficient instruments of prehension, 

 and they accordingly fix their body by means of 

 them to the plane of position, while the head and 

 anterior part remain free. The abdominal legs of 

 the others, on the contrary, are mere points of sup- 

 port, incapable of clinging to an object, and the 

 larva consequently fixes itself by its pectoral or 

 forelegs, which are much developed for the purpose. 

 The whole of the abdominal portion of the body 

 is thus left at liberty, and it is either borne curved 

 inwards, (as in the gooseberry saw-fly,) or projects 

 into the air in variously contorted and singular 

 postures, as is remarkably exemplified in the wil- 

 low saw-fly, (Nematus Caprece,) and the larva of 

 Hylotoma Rosse, which has the extremity of its 



