INTRODUCTION. 2$ 



dimensions of their bodies, would not appear to be on account of 

 their muscles being more numerous than those of vertebrate animals, 

 but on account of greater intrinsic energy and muscular activity. 

 The articulations of insects may be considered as solid cases which 

 envelop the muscles, and the thickness of these cases appears to 

 decrease in a singular manner according to the size of the creature. 

 The relative bulk of the muscles being less in the smaller species 

 than in the larger, it is necessary to explain the superior relative 

 strength of the former by supposing them to possess a greater amount 

 of vital energy. 



These astonishing phenomena will perhaps be better understood 

 if we consider the obstacles which insects have to overcome to satisfy 

 their wants, to seek their food, to defend themselves against their 

 enemies, &c. 



To meet these requirements they are marvellously constructed 

 for both labour and warfare, and their strength is superior to that dis- 

 played by all other animals. It is also much greater than that of the 

 machines we construct to replace manual labour. They represent 

 strength itself God's workmen are infinitely more powerful than 

 those invented by the genius of man, which we call machines. 



We think it necessary, in closing this chapter, to give a sort of 

 general outline of the great class of animals which we are about to 

 study. If we wished to characterise insects by their exterior aspect, 

 we might consider them as articulate animals, whose bodies, covered 

 with tough and membranous integuments, are divided into three 

 distinct parts : the head, provided with two antennae, and eyes and 

 mouth of very variable form ; a trunk or thorax, composed of three 

 segments, which has underneath it always six articulated limbs, and 

 often above it two or four wings; and an abdomen, composed of 

 nine segments, although some may not appear to exist at first sight. 



If, in addition to these characteristics, one considers that these 

 animals are not provided with interior skeletons — that their nervous 

 system is formed of a double cord, swelHng at intervals, and placed 

 along the underside of the body, with the exception of the first 

 swellings or ganglions which are under the head — that they are not 

 provided with a complete circulating system — that they breathe by 

 particular organs, termed tracheae, extending parallel to each other 

 along each side of the body, and comnmnicating with the exterior 

 air by lateral openings termed spiracles — that their sexes are distinct 

 — that they are reproduced from eggs — and, in conclusion, that the 

 different parts we have mentioned are not complete until the creature 

 has passed through several successive changes, called metamorphoses, 



