OF INSECTS. 
309 
more than sixteen feet, while the larvee 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 
Humber 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 Rosae, which has the extremity of its 
