634 EXTERNAL ANATOMY OF INSECTS. 
rus in the middle; in Strategus Aloeus beyond the mid- 
dle*; in Tenebrio Molitor near the apex; and in Dytiscus 
marginalis there appears to be no joint at all; but the 
fact is, that in this insect the postcosta,—the termination 
of which really forms the joint, the costa itself being only 
flexible at that point,—stands at a greater distance from 
the latter at its end.. Well, at this joint the above fold 
is made, the apex of the wing, being first folded longi- 
_ tudinally, turning under and inwards, and forming an 
angle, more or less acute, with the joint or costal margin, 
so that the fold is not quite but nearly transverse: this 
at least is the case in Geotrupes stercorarius and other 
Lamellicorns: in Staphylinus, &c., there are several 
transverse and longitudinal folds, and thus the wing is 
more easily packed under the short elytra; in Molorchus, 
Necydalis, &c., in which it is left uncovered, except at its 
base, the anal fold takes place, and the apical in some 
degree ; a short portion near the apex forming an obtuse 
angle with the margin; in Atractocerus the wing appears 
to be only longitudinally folded; and in Buprestis vittata 
only the anal fold is to be detected. Besides these trans- 
verse and longitudinal folds these organs, in many bee- 
tles, haye an infinity of fine corrugations, which ramify 
like the nervures of the tegmina of Flata®, &c., proceeding 
from the Costal Area or the disk of the wing to the pos- 
terior margin; the object of these plicatures is doubtless 
to present a more ample surface to the action of the at- 
mosphere in flight®. When all these folds have been 
made in a Coleopterous wing, the apex of the one at 
@ Prate X. Fie. 4. 0”. 
» See above, p. 610. 
* See above, p. 611, and Chabrier Analyse, &c. 24. 
