LETTERS ON ENTOMOLOGY. 33 
LETTER IV. 
MY DEAR FRIEND, 
I must endeavour to give you some 
idea of the peculiar characters which distinguish 
the class of insects from other animals. First, 
they are furnished with several feet, not fewer 
than six (for those butterflies which appear to 
have only four legs, have also two false ones), 
and sometimes with a great many. Secondly, 
their flesh is affixed to the internal surface of 
their skin. Thirdly, they breathe not by lungs 
or gills, but by a sort of spiracles or breathing 
holes, situated at certain distances along each 
side of the body; and lastly, the head is ge- 
nerally furnished with a peculiar pair of pro- 
cesses, called Antennae, or jointed horns, which 
vary extremely, but are equally important organs 
to all. 
Linnaeus divides all insects into seven orders ; 
Coleoptera, Hemiptera, Lepidoptera, Neuroptera, 
Hymenoptera, Diptera, and Aptera. Coleoptera 
contains all insects of the beetle tribe, or such 
c5 
