INSECTS. — GENERAL CHARACTERISTICS. 
3 
interested in agricultural pursuits. For tlieir use, chiefly, 
this account of the principal insects that are injurious to 
vegetation in New England, has been prepared. It has 
been thought best to prefix thereto some remarks on the 
structure and classification of insects, to serve as an intro¬ 
duction to the succeeding chapters, and, in some measure, 
to supply the Avant of a more general and complete Avork 
on this branch of natural history. 
The Avord Insect^ AAdiich, in the Latin language, from 
AAdience it Avas deriA^ed, means cut into or notched, Avas 
designed to express one of the chief characters of this 
group of animals, Avhose body is marked by seAnral cross- 
lines or incisions. The parts betAveen these cross-lines are 
called segments, or rings, and consist of a number of jointed 
pieces, more or less moAnble on each other. 
Insects liaAn a very small brain, and, instead of a spinal 
marroAv, a kind of knotted cord, extending from the brain to 
the hinder extremity ; and numerous small Avhitish threads, 
AAdiich are the neiwes, spread from the brain and knots, in 
various directions. Tavo long air-pipes, AAdthin their bodies, 
together AAuth an immense number of smaller pipes, supply 
the Avant of lungs, and carry the air to eA^ery part. Insects 
do not breathe through their mouths, but through little 
holes, called spiracles, generally nine in number, along each 
side of the body. Some, liOAveA^er, haA^e the breathing-holes 
placed in the hinder extremity, and a feAv young Avater- 
insects breathe by means of gills. The heart is a long tube, 
lying under the skin of the back, haAdng little holes on each 
side for the admission of the juices of the body, AAdiich are 
preA^ented from escaping again by A^ah^es or clappers, formed 
to close the holes within. iNIoreoA’er, this tubular heart is 
diAdded into seAwal chambers, by transA^erse partitions, in 
each of Avhich there is a hole shut bA" a A^ah^e, Avliich alloAvs 
the blood to floAv only from the hinder to the fore part of the 
heart, and preA’ents it from passing in the contraiy direction. 
The blood, AAdiich is a colorless or yelloAV fluid, does not cir- 
