180 PTILOTA. 



complete metamorphosis, and the latter an incomplete one ; 

 but as these terms have also been employed by Linnaeus and 

 Fabricius in a more restricted and totally different sense, and 

 as they have been applied to designate the entire metamor- 

 phosis, instead of simply indicating the formation of the larva, 

 I prefer dividing insects, from a consideration of their larvae, 

 into two divisions, which may be named Heteromorpha and 

 Monomorpha, from the dissimilarity or resemblance of the 

 larva with the imago. 



In all this diversity, however, there is still a general pre- 

 vaiUng uniformity of structm'C, which, under various modifi- 

 cations of form, preserves a tendency towards one typical 

 organization. This typicality in larvae consists in having 

 the body ordinarily composed of thirteen segments, which 

 are for the most part of an equal size, although, when arrived 

 at maturity, some of these segments become obsolete, being 

 converted into internal organs, or are greatly altered as 

 regards the extent of their individual developement. Here 

 the entire object of the animal's existence consists in its 

 capability of feeding ; consequently, owing to the formation 

 of the internal digestive organs, the body maintains through- 

 out its various segments a general conformity, none requir- 

 ing an extra developement for the support of organs fitted 

 for other purposes. When, however, the insect has arrived 

 at the perfect state, its objects are completely altered, — it has 

 now to seek its mate ; it is therefore provided with wings, 

 which, requiring support from the segments to which they 

 are attached, cause these segments to be necessarily deve- 

 loped in an extraordinary degree ; the other adjacent seg- 

 ments being losers : the insect has also now to perform the 

 great object of its existence, namely, the continuing of its 

 kind, and therefore the organs of generation become organs 

 of especial importance, and we accordingly find other por- 

 tions of the body sacrificed for their developement. 



