570 EXTERNAL ANATOMY OF INSECTS, 
vertex truncated or open; but in Copris the triangle is 
equilateral. In the other Orders it is little more than 
the central posterior point of the postdorsolum*. 
11. Postfrenum®. The part now mentioned is much 
more important than the preceding one, and must not be 
passed over so cursorily. In the Coleoptera it usually 
presents itself under the form of two Jarge and usually 
rather square pannels, the disk of which is convex, but 
the rest of their surface unequal, which are situated one 
on each side of the postscutellum*; under the anterior 
outer angle of these is the socket or principal attachment 
of the secondary wings, and their basal margin is at- 
tached to their outer side; posteriorly behind the vertex 
of the postscutellum the postfranum is crowned with a 
ridge or bead, below which it descends vertically or ob- 
liquely to the abdomen ; this ridge often turns upwards, 
and proceeds towards the middle of the basal margin of 
the wing. In the Petalocerous beetles the part in ques- 
tion is usually more or less hairy; but in many others, 
as the rose-scented Capricorn (Cerambyx moschatus), 
&c. it is naked. At its side you will commonly observe 
several plates and tendons (osselets Chabr.) connected 
inter se and with the base of the wing by elastic liga- 
ments, which are calculated to facilitate the play of those 
organs. In the Orthoptera, Neuroptera, and Homopte- 
rous Hemiptera, the postfrenum does not differ mate- 
rially from the frenum*. In the Heteropterous section 
of the last Order it is usually a transverse ridge termi- 
nating the postdorsolum, with a bifurcation where it 
2 Prats VIII. Fic. 12. uv’. Prate IX. 7. u. 
» Prates VIII. TX. ov’. © Prate VIII. Fic. 3. v'. 
4 Ibid. Fic. 12, 16.; and Prats IX. Fic. 7, v'. 
