NATURAL HISTORY. 3 
body, and is furnished with two antenne, or 
horns. ‘True insects have only six articulated 
thoracic feet, and all of them, except the orders 
Thysanura and Anoplura,* of Dr. Leach, 
undergo certain changes or metamorphoses 
(more or less complete) before they arrive at 
their final or perfect state, in which alone they are 
capable of propagation. In the first state they 
are called larvee, worms, grubs, or caterpillars ; 
the second, pupe or crysalides, in which they 
are mostly inactive; and the last is the imago, 
or perfect insect. Their distinctive characters 
in this latter condition are the basis on which 
entomologists have classified them into orders, 
sections, families, genera, and species. The 
most minute differences have been recorded of 
the perfect insect ; but, in the first or larva state, 
the descriptions are so meagre, especially of the 
aquatic, that in many instances it is impossible 
to ascertain the precise species to which they 
belong. This, however, is of little import in 
the view here taken of them. 
* The order Parasita of Cuvier and Latreille. These are not 
included with insects by later entomologists. 
