INTRODUCTION. 9 



to the lower lip, and one or two to each of the lower jaws. The 

 mouth of sucking-insects consists essentially of these same parts, 

 but so different in their shape and in the purposes for which they 

 are designed, that the resemblance between them and those of 

 biting-insects is not easily recognised. Thus the jaws of cater- 

 pillars are transformed to a spiral sucking-tube in butterflies and 

 moths, and those of maggots to a hard proboscis, fitted for pier- 

 cing, as in the mosquito and horse-fly, or to one of softer consist- 

 ence, and ending with fleshy lips for lapping, as in common flies ; 

 while in bugs, plant-lice, and some other insects resembling them, 

 the parts of the mouth undergo no essential change from infancy 

 to the adult state, but are formed into a long, hard, and jointed 

 beak, bent under the breast when not in use, and designed only 

 for making punctures and drawing in liquid nourishment. 



The parts belonging to the thorax are the wings and the legs. 

 The former are two or four in number, and vary greatly in form 

 and consistence, in the situation of the wing-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 larvae and 

 pupae of those that are subject only to a partial transformation. 

 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 larvae 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 seg- 

 ments, and sometimes an additional fleshy prop-leg under the 

 hindmost extremity ; caterpillars and false caterpillars have, be- 

 sides 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 

 2 



