THE METAMORPHOSIS. 49 



that there are a few which leave the egg in a form 

 exactly similar to that of their parents, and which are 

 consequently subject to no metamorphosis, these 

 creatures are destitute of wings, or apterous, at all 

 periods of their lives. Examples of apterous insects 

 occur in almost all the orders, but in most cases 

 these are easily referred to their proper stations from 

 the consideration of their general characters ; there 

 are, however, a few orders in which the absence of a 

 metamorphosis is a constant phenomenon, and these 

 are by most entomologists placed in a group by them- 

 selves, which evidently serves to connect the true In- 

 sects with the other groups of articulated animals and 

 especiaHy with the Myriapoda*. 



On referring to the definition of an insect which 

 we have adopted in the first chapter, and comparing 

 it with the more detailed account of the general 

 structure of insects given in the second, we shall find 

 not only that its propositions are confirmed, but also 

 that as regards the majority of insects we may add to 

 it considerably. In the examination of the structure 

 of the larvse of these creatures, on the contrary, we 

 find that many of the characters upon which our de- 

 finition was founded no longer appear, in the larvae 

 of insects with a complete metamorphosis, the division 

 of the body into three regions is not to be seen, and 

 even the head and legs are wanting in some cases, so 

 that if common characters were required which might 

 include all insects in all stages of their existence, we 

 should be reduced to call them air-breathing Articu- 

 lata, a definition which is rather too vague to be 

 satisfactory. Loose as it would be, however, it would 

 still be inapplicable to the preparatory states of many 

 * See p. 3. 



D 



