1924 ] 
How a Beetle Folds its Wings 
257 
in fact very important sclerite which the tracheation shows to be 
a fragment of vein Rs. It is thrown into a horizontal position 
and supported by the tension between A and B, exactly as in 
the Lampyrid. The fragment of vein M represented by bar G 
is also apparently of some use, though as it is crossed by one of 
the folds it must be flexible, and is resistent only to compression. 
It no doubt helps to fix the bases of M and N. The outer part 
of the wing is held flat in a curious way. E as already stated can 
be bent back, but not up or down, on account of its peculiar 
structure; and it is attached at its outer end to a large area 
supported by a complex of strong veins (HILKJ). This area 
is only kept from bending up or down by the support of E, and 
is kept forward by the support of the tip of F, which articulates 
with it and pushes against it, as can be demonstrated by cutting 
E and F in turn. The tip of J may also get some support from 
the tip of G, which will help keep the whole area from bending 
down obliquely by twisting X. Altogether the whole area seems 
very weakly supported, but I can find no other factor. HILKJ, 
in turn, supports the entire posterior part of the wing by tension 
in the direction indicated by chain-lines on the diagram. This 
pull has to act against a strong spring-like action of the root of 
0, which tends to fold up the wing, and it seems surprising that 
the bracing of H by F is strong enough to do it. The apex of the 
wing is supported by S in relation to I and M, and by T in re- 
lation to M and S, in much the same way as S is supported by 
K and N in the Lampyrid. 
Other Adephaga show a great deal of variation, especially 
in the outer part of the wing; but I believe the relation between 
X, F and H, to stiffen the outer part of the wing, is functional in 
all. 
It will be interesting to compare other beetles with these 
two principal types of folding, and especially to find if any other 
mechanism is made use of. As I said at the start, I have a 
strong suspicion that in the various Clavicorn groups there are 
still other methods of folding, and some seem to make use of the 
feet. But careful observation of living specimens will be ne- 
cessary to settle the matter. I hope this paper will attract some 
good observers to a very interesting problem. 
