402 EXTERNAL ANATOMY OF INSECTS. 



meso- and metathorax, ^^ pectus.'''' Stvaus-Durckheim calls the 

 prothorax, " corselet," and the other two segments the thorax. 

 Lastly, MacLeay and Burmeister, following Andouin, consider 

 the three segments perfectly distinct, and ado})t for them the 

 same names ; yet these writers still seem to suppose some con- 

 nexion between these segments, which essentially insulates 

 them from the rest, and therefore apply to the three united 

 the name of thorax. Beyond the nomenclature of these four 

 segments, reckoning the head as one, nothing has been done 

 yet in description; we find the second, third, fourth, &c. 

 segment of the abdomen, constantly spoken of and described, 

 without the slightest hint being given to us from which segment 

 we are to commence counting. 



Before entering more minutely into those variations of the 

 thirteen segments on which subdivision will be found to depend, 

 permit me to make a few observations on the preparatory and 

 highly important state of larva. Every true insect must pass 

 through this state previously to arriving at perfection ; and as 

 its habits are more slugglish, and its occupation (that of eating) 

 more uniform, and as its life is usually confined to a single 

 medium, and its movements to a single mode of progression, 

 it seems evident that no one segment need be particularly 

 enlarged or strengthened at the expense of the others : we 

 find this not only theoretically, but positively the case ; and, 

 consequently, each of the thirteen segments is regularly and 

 uniformly developed; and from this circumstance, and the splen- 

 did discoveries of insect anatomists, who have detected every 

 part of the imago in the larva, in the very position, or nearly so, 

 which it is destined eventually to occupy, it may, I think, with- 

 out incurring a charge of theorizing, be taken for granted, that 

 every segment of the larva still exists in the imago, although 

 its presence, owing to the development of a neighbouring seg- 

 ment, may be in some instances somewhat difficult to detect. 

 It would be a dehghtful task to trace each segment in its 

 increase or decrease as it passed through the intermediate state 

 of pupa, but this will scarcely be accomplished by a single 

 individual, as the number of specimens to be examined, and 

 the difficulty of obtaining sufficient specimens of all the classes, 

 in each of the stages, would render the undertaking rather a 

 laborious one. In order to show the uniformity of structure 

 in larvce, I have drawn a few outlines of tliose whose imagines 



