EXTERNAL ANATOMY OF INSECTS. 529 
upper part thorax superior and the lower thorax inferior. 
M. De Blainville, M. Latreille, and other French wri- 
ters, improved upon this, naming the upper part the 
back (dorsum), 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 fruns, 
thorax, and breast, in the common acceptation are well 
understood, and lead to no confusion or glaring impro- 
priety ; I shall therefore adhere to the old phraseology, 
especially as French Entomologists in popular language 
still do the same. 
As to the division of the trunk into segments by M. 
Latreille 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—pro- 
thorax, mesothorax, metathorax. ‘The first of these seg- 
ments, however—and the learned Entomologist just 
named seems to hint as much*—is usually more distinct 
from the other two, than they are from each other. If 
this idea be correct, the trunk is properly resolvable into 
two primary segments, the first bearing the arms or fore- 
legs, and the other the proper legs and the organs of 
flight. M. Chabrier calls the latter tronc alifére, or 
wing-trunk ;—a happy term, which I have adopted and 
latinized, calling it the alitrunk (alztruncus): the first 
segment, because it bears the fore-legs, I have named 
manitrunk (manitruncus). I adopt likewise the terms 
above mentioned, prothorax, mesothorax, metathoraz, 
to signify the three segments into which the thorax of 
* Organisation, §&c. 198. 
VOL. III. 2M 
