Thorax in winged Insects. 165 
lopement with respect to the number of pieces, for the developement of 
any one or more of them, in point of size, will occasion the neighbouring 
ones more or less to diminish, and even to disappear. 
The antefurca, medifurca, and postfurca compose one internal whole 
that Audouin calls the entothorax, and Kirby, following M. Chabrier, the 
endosternum. The entothorax sometimes extends into the head of 4n- 
nulosa and sometimes into the abdomen. In the thorax it is composed of 
six pieces, and serves to keep the cesophagus and intestine in situ. 
Now to apply the foregoing remarks to some particular cases of struc- 
ture. The difference betweena Trichius and a Cetonia, or between a 
Goliathus of America and a Goliathus of Africa, is that in the latter of 
the two the epimeron of the mesothorax is remarkably developed. The 
difference between an Athyreus and @ Geotrupes is that the scutellum of 
the mesothorax is remarkably developed in the latter: but the greatest 
developement of this piece among Coleoptera is in the genus Macraspis. 
The great developement of the prothorax in some Coleoptera, as Gnoma, 
and in certain Orthoptera, as Locusta, occasions the mesothorax to be less 
developed in proportion. If, as in Phasma, the prothorax be small, then 
the mesothorax is excessively great, and this latter part takes its greatest 
developement in the Hymenoptera, Trichoptera, Lepidoptera, and Dip- 
tera. M. Audouin observes, that if an insect (such as a Carabus, or as 
Coleoptera in general) be eminently a walker, the pectus of the thorax is 
most developed ; and if another, such as a moth, or Lepidoptera in gene- 
ral, be eminently a flier, then the tergum of the thorax is most developed. 
But this observation must be cautiously adopted; for the tergum of the 
thorax is excessively developed in some insects eminently walkers, as 
for instance, a female Phasma, which is apterous. 
Owing to the great developement of the mesothorax in Hymenoptera 
the prothorax is diminished in size, but not to the degree that Mr. Kirby 
supposes. I agree most decidedly with MM. Audouin and Bennett * in 
thinking that the collar belongs to the prothorax, and shall now attempt 
® The entomological student ought particularly to refer to what my learned 
friend, E. T. Bennett, Esq., says on this subject in his excellent Epitome of 
M. Chabrier’s Observations on the Anatomy of the Thorax in Insects, Zool, 
Journal, Vol. I. p. 392. 
