533 APPENDIX. 



refer to the bone of the hip. Secondly, from a careful examination ot son;e 

 species of every order of insects, I am now persuaded that both Illiger and 

 we are wrong, also, in considering the Coxa as formed of two parts, and the 

 Ischium as forming one of them. On the conitraiy, it is clearly a part of 

 the thigh, to which it. is generally closely attached by a membrane admitting 

 only a very slight degree of motion, but perhaps never by a distinct joint. 

 The joint is always between the Ilium and the Ischium, the latter serving 

 as a sort of fulcrum to the base of the thigh, often with a hole between theni 

 for the reception of the pivot of the Hium. If you will dissect and examine 

 a large foreign Geotrupes, you will see all this very clearly. You will find 

 that even when the insect has had its joints made pliant by being immersed 

 in hot water, there is little or no motion can be produced between the Ischium 

 and the thigh, which are attached to each other by that articulation called 

 by anatomists amphiarthrosis ; whereas there is a distinct ginylymns joint be- 

 tween the Hium and the Ischium. It is true that in Hymenoptera, Diptera, 

 and some Coleoptera, where the Ischia are not fixed obliquely to the base 

 of the thigh, but transversely, the Ilium and Ischium do seem at first view 

 like the two parts of one joint ; but even then, as I have ascertained by 

 examining living insects, the Ischium is still fixed to the thigh by a mem- 

 brane and no joint, and the joint is still between the Ischium and Ilium. 

 Now, such being the facts, there cannot, I think, be a moment's hesitation 

 in deciding that it can never be proper to consider a part as forming a portion 

 of a limb with which it is connected by a true ginglymus joint ; or not to 

 consider it as portion of a limb with which in many cases it seems truly 

 connate, and in all others closely connected by a membrane admitting of littlo 

 or no motion. It appears to me, therefore, that our Ilium should be regarded 

 as a peculiar and distinct joint, namely, the true hip-joint ; and we cannot 

 have a better name for it than Coxa, which Latreille also gives to it. Our 

 Ischium must be considered part of the thigh, and cannot, I think, have a 

 better name than Trochanter, which has the right of priority, and, though not 

 strictly anatomically correct, is as near as in such cases we can expect to 

 come : both are processes of the base of the thigh ; only in man the trochanter 

 is a mere projection of the base of the thigh ; in insects a distinct part 

 joined by a suture and membrane. Observe, some Ichneumons have a double 

 trochanter. 



" I particularly wish you would examine the claw-joint of the tarsi of a 

 large Cerambyx, Leptura, or Chrysomela, and I think you will agree with n)e 

 that the small part of the base, though separated by a suture, is no distinct 

 joint, but in fact a trochanter aflBxed to the claw-joint by the anarthrosis articu- 

 lation, and very closely analogous to the trochanters of the thighs. To me it 

 seems that it would be quite as proper to consider this minute basal part a por- 

 tion of the third joint (not of the claw-joint) of the tarsi as to call the trochan- 

 ters parts of the Coxjb. Attention to the mode of articulation (evidently a 

 material point) will lead to another good consequence — we can thus avoid 

 regai'ding this supplementaiy part in the tarsi of Leptura, &c. as a true joint, 

 the reverse of which would sadly curtail our grand divisions founded on the 

 tarsi ; and, by calling it a trochanter, we may possibly gain some good generic 

 characters, if, as I suspect, the same circumstance holds good in some other 

 tribes. 



" I have been puzzling myself a good deal to discover what parts in the 

 posfpectus of Hymenoptera and Coleoptera are analogous to each other. I have 

 not yet by any means satisfied myself on every point, but two or three fixed 

 landmarks I think I have ascertained. One is, that your Collare (' Monograph. 

 Apum Ang.') is not, as we have supposed, analogous to the upper part of the 

 thorax in Coleoptera. I was made pretty sui"e of this in the course of dissect- 



