EXTERNAL ANATOMY OF INSECTS. 531 



proved upon this, naming the upper part the back (dor- 

 sum), and the lower the breast (pectus); and dividing the 

 trunk, or according to them thorax, into three sections, 

 each bearing a pair of legs. But I see no sufficient reason 

 for this alteration — the terms trunk, thorax, and breast, 

 in the common acceptation are well understood, and lead 

 to no confusion or glaring impropriety ; I shall therefore 

 adhere to the old phraseology, especially as French En- 

 tomologists in popular language still do the same. 



As to the division of the trunk into segments by M. La- 

 treille and others, it has been regarded as consisting of 

 three primary ones, which have been called in the order 

 of their occurrence, reckoning from the head — prothorax, 

 mesothorax, metathorax. The first of these segments, 

 however — and the learned Entomologist just named seems 

 to hint as much a — is usually more distinct from the other 

 two, than they are from each other. If this idea be cor- 

 rect, the trunk is properly resolvable into two pi'imary 

 segments, the first bearing the arms or fore-legs, and the 

 other the proper legs and the organs of flight. M. Cha- 

 brier calls the latter tronc alifere, or wing-trunk; — a 

 happy term, which I have adopted and latinized, call- 

 ing it the alitrunk (alitrmicus) : the first segment, because 

 it bears the fore-legs, I have named manitrunk (mani- 

 truncus). I adopt likewise the terms above mentioned, 

 prothorax, mesothorax, metathorax, to signify the three 

 segments into which the thorax of Linne, or the upper 

 side of the trunk, is resolvable; and those of the breast 

 I denominate antepectus, medipectus, and postpectus. If 

 terms be thought necessary to designate the two intire 



a Organisation, #r, 198. 

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