INSECTS. — GENERAL CHARACTERISTICS. 3 



interested in agricultural pursuits. For their 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 want of a more general and complete work 

 on this branch of natural history. 



The word Insect, which, in the Latin language, Irom 

 whence it was derived, means cut into or notched, was 

 designed to express one of the chief characters of this 

 group of animals, whose body is marked by several cross- 

 lines or incisions. The parts between these cross-lines are 

 called segments, or rings, and consist of a number of jointed 

 pieces, more or less movable on each other. 



Insects have a very small brain, and, instead of a spinal 

 marrow, a kind of knotted cord, extending fi-om the brain to 

 the hinder extremity ; and numerous small whitish tlu-eads, 

 which are the nerves, spread from the brain and knots, in 

 various directions. Two long air-pipes, witliin their bodies, 

 together with an immense number of smaller pipes, supply 

 the want of lungs, and carry the au" to every 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, however, have the breathing-holes 

 placed in the hinder extremity, and a few young water- 

 insects breathe by means of gills. The heart is a long tube, 

 lying under the skin of the back, having little holes on each 

 side for the admission of the juices of the body, which are 

 prevented from escaping again by valves or clappers, formed 

 to close the holes within. Moreover, this tubular heart is 

 . divided into several chambers, by transverse partitions, in 

 each of which there is a hole shut by a valve, which allows 

 the blood to flow only from the hinder to the fore part of the 

 heart, and prevents it from passing in the contrary direction. 

 The blood, which is a colorless or yellow fluid, does not cir- 



