EXTERNAL ANATOMY OF INSECTS. 407 



organs arising from them have to perform, and this not always 

 directly, but relatively, as the functions of the organs which one 

 segment may bear, frequently influence the next segment on 

 either side in a greater degree than the segment more imme- 

 diately concerned. The segment in question supports the 

 caput, or head, and joins at its opposite margin the meso- 

 tJiorax, being articulated to both by a perfectly free joint, 

 moveable in any direction : it bears also the jiropedes, or fore- 

 legs, which are articulated to it with perfectly free joints, and 

 which have generally a tendency to stretch forward. In 

 Lep'idoptera, the prothorax is a narrow ring, or circular 

 collar, on which the scales are generally more erect than on 

 the mesothorax, a circumstance which renders it easy to be 

 seen externally, and without removing the scales ; in the 

 PteropJiori, however, it is scarcely to be detected. In the 

 Diptera, all external appearance of the prothorax (at least 

 from above) has ceased," the caput and mesothorax seem to 

 be articulated together, and the fore-legs to spring from the 

 joint which unites them ; directly we leave the Diptera 

 you will observe the prothorax reappearing among the bees, 

 more prominent in the Spheces, and a very important segment 

 in the genera Sirex and (particularly) Cejjhus : " these genera 

 probably lead to the Coleoptera, in which the prothorax is 

 remarkably conspicuous ; but it is not until the next class, 

 Orthoptera, that it attains its fullest development, where, 

 especially among the Grylli BuUcb of Linnaeus, it seems to 

 have reached its maximum, being frequently of gi'eater magni- 

 tude than all the remainder of the insect ; in Hemiptera also 

 we find the prothorax occasionally of prodigious relative 

 magnitude, but it gradually decreases until, in Cicada, it has 

 become a mere collar, and finally merges in the Lepidopterous 

 form with which I commenced.'' 



^ With some few exceptions. 



^ Also in the Chalcides, and above all in Agaon. 



* If among your readers there should be some who wish to learn — which I fear 

 there scarcely will be, as it is the infallible consequence of publishing in such a 

 channel, to be read by those who know more on these subjects than oneself — if, 

 I say, there be those who wisli to learn, I will offer for their use a few very 

 simple observations : 1 have already stated that the prothorax produces the fore- 

 legs, the mesothorax the fore-vfings and middle-legs, and the metathorax the 

 hind-wings and hind-legs ; if, therefore, an insect be accurately dissected, these 

 parts will adhere to the segment to which they naturally belong. In order to try 



