8 INSECTS IXJUPJOUS TO VEGETATION. 



The parts belonging to the thorax are the wings and the 

 legs. The former are two or fovu' in number, and vary greatly 

 in form and consistence, in the situation of the Aving-bones or 

 veins, as they are generally called, and in their position or the 

 manner in which they are closed or folded when at rest. The 

 under-side of the thorax is the breast, and to this are fixed the 

 legs, which are six in number in adult insects, and in the larvse 

 and pupGB of those that are subject only to a partial transfor- 

 mation. The parts of the legs are the hip-joint, by which the 

 leg is fastened to the body, the thigh, the shank (tibia), and the 

 foot, the latter consisting sometimes of one joint only, more 

 often of two, three, four, or five pieces (tarsi), connected end to 

 end, like the joints of the finger, and armed at the extremity 

 with one or two claws. Of the larvte that undergo a complete 

 transformation, maggots and some others are destitute of legs; 

 many grubs have six, namely, a pair beneath the under-side of 

 the first three segments, and sometimes an additional fleshy 

 pro)>leg under the hindmost extremity ; caterpillars and false 

 caterpillars have, besides the six true legs attached to the first 

 three rings, several fleshy prop-like legs, amounting sometimes 

 to ten or sixteen in number, placed in pairs beneath the other 

 segments. 



The abdomen, or hindmost, and, as to size, the principal part 

 of the body, contains the organs of digestion, and other internal 

 parts, and to it also belong the piercer and the sting with which 

 many winged or adult insects are provided. The piercer is 

 sometimes only a flexible or a jointed tube, capable of being 

 thrust out of the end of the body, and is used for conducting 

 the eggs into the crevices or holes where they are to be laid. 

 In some other insects it consists of a kind of scabbard, con- 

 taining a central borer, or instruments like saws, designed for 

 making holes wherein the eggs are to be inserted. The sting, 

 in like manner, consists of a sheath enclosing a sharp instrument 

 for inflicting wounds, connected wherewith in the inside of the 

 body is a bag of venom or poison. The parts belonging to the 

 abdomen of larvae are various, but are mostly designed to aid 

 them in their motions, or to provide for their respiration. 



An English entomologist has stated, that, on an average, 

 there are six distinct insects to one plant. This proportion is 



