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 

 endosternuni. The entothorax sometimes extends into the head of An- 

 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 between a Trichius and a Cetonia, or between a 

 Goliathus of America and a Goliathus of Africa, is that in the latter of 

 the two the epiraeron of the mesothorax is remarkably developed. The 

 difference between an Athyreus and a 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 Oithoptera, 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" 

 fera. M. Audouin observes, that if an insect (such as a Carabus, or aa 

 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 tergura 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. 



