APPENDIX. 599 



in conceiving that the thorax, as it has been usually called, in Coleoptera is not 

 analogous to the collare in Hymenoptera, and thus to do you ample justice for 

 that penetration and discernment which enabled you so early to rmike this very 

 important discovery. Truth seemed to me at first on the other side; but the 

 observations I have made this spring, and another circumstance, which I shall 

 presently explain to you, have made me a convert to your sentiments. If I 

 know myself I love truth better than opinion ; and though I may be sometimes 

 over warm, from the natural hastiness of my temper, in maintaining what ap- 

 pears to me so at the time, yet I am never backward to own and embrace it, 

 however contrary to my former opinions, when, the clouds being removed, I see 

 it in its native beauty. In my last letter you observed, I dare say, that I was 

 become nearly of your opinion; I will now state what has made my conviction 

 complete. After I had finished the Orismology, I thought to begin the Letter 

 Avhich treats of the body of an insect considered more at large. Beginning 

 with the crust, or skeleton, I next turned my attention to its articulations, dis- 

 tinguishing those that have free motion, I mean motion independent of that 

 of the parts to which they are attached on any side. In this view, taking a 

 coleopterous insect for my example, the body to me appeared to consist of 

 four, instead of three great joints viz. the head, the thorax, the metathorax, 

 and the abdomen. (With respect to the two last, the metathorax and the 

 abdomen, they are much more closely connected in this order than the head 

 and the thorax. I have not yet ascertained by observation whether they have 

 free motion ; but as they certainly have in Hymenoptera, &c., I for the present 

 take it for granted.) Considering, then, that the upper part, or shield, of the 

 thorax moves with the under part or breast, and together form the second joint, 

 this convinced me that the collar in Hymenoptera, which has no free motion, 

 and is therefore part of the metathorax, with which it moves, could not be re- 

 garded as analogous to the shield of the thorax, which moves with the breast, 

 independently of the metathorax. The instances referred to in my last, viz. 

 Fanus and Xyphydria, in which the breast is evidently independent of the 

 collar, confirm this triumphantly. So in Hymenoptera, as well as Coleo- 

 ptera, there are four free divisions; for I imagine that, although the head can 

 move the thorax or breast, yet the breast can move (as in Coleoptera) inde- 

 pendently of the head: but this, observation must ascertain. This grand dis- 

 covery of yours leads to some very important consequences, affording an 

 admirable clue for a new order, and also for two great divisions of insects 

 viz. into Tlioracici and Collares; the latter subdivisible into Collares, Collari 

 distincto, and Collari evanescente. The Thoracici would include Coleoptera, 

 Orthoptera, Hemiptera, and Neuroptera (excluding Phryganea and Psocus); 

 and the Collares, Collari distincto, Hymenoptera, Trichoptera ?, and Lepido- 

 ptera?; and the collar es collari evanescente would contain the Diptera. As to 

 the Aptera, I cannot at present speak in this respect. With regard to my new 

 order Trichoptera, every hour more convinces me of the propriety of it. Jn the 

 Libellulidae, Myrmeleon, Ascalaphus, Hemerobius, Semblis, Ephemera, Raphidia, 

 &c., the pectus is covered by a thoracic shield; but in Phryganea and Psocus, 

 and Panorpa ? it is not. I have no specimen of Termes to enable me to as- 

 certain to which of these it belongs ; but, from the veins of the wings, I 

 should suspect to the latter. Upon looking again at Panorpa, it seems to have 

 a small thoracic shield ; and as its wings have veins as well as nerves, it pro- 

 bably belongs to the genuine Neuroptera : I wish much to have your sen- 

 timents upon this idea. I use the term Trichoptera, because most of the insects 

 (the genus Psocus excepted) that belong to this order have hairs upon their 

 wings, and it distinguishes them, I think, well from their affinities, the Le- 

 pidoptera. The next thing to be considered is, by what name we shall de- 

 nominate the shield of the thorax in the thoracic insects : for certainly the term 



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