528 How Cockroaches and Earwigs fold their Wings. [September, 
with the wing of a cockroach, its nearest ally, and the purport of 
the anomaly will appear when we examine carefully the closure 
of the wing. 
Suppose this wing expanded. to its utmost. It is retained in 
its place by muscles which act upon two sets of veins ; an anterior — 
set which supports the coriaceous base of the front part of the 
wing, giving a certain strength and solidity to the whole; and a 
posterior set which holds at arm’s length, as it were, and there- 
fore at great disadvantage, the body of the wing, hinging upon 
the extremity of the second anal branch which runs from base to 
mid-wing. Let the latter support be relaxed and the fan closes 
at once ; the pivoting point is seen to be the very bottom of the 
incision of the wing next the apex of the coriaceous portion, an 
incision in the middle of the front border of the wing, corre- 
sponding to the anal emargination of the apex of the wings of 
certain cockroaches and to that of the middle of the hind border 
of most insects. When this fan of the anal field is closed, the 
plications are brought beneath that portion of the wing which 
lies between the extended vein which supports the rays and the 
lower edge of the coriaceous base of the wing. Since the coria- 
ceous base does not extend quite to the middle of the expanded 
wing, the wing by this process is at once reduced to less than 
half its length ; and the former apex for the same reason now 
overlaps the base and rests beside it against the body ; the width 
of the wing being also reduced, the entire area is now less than 
one sixth its former extent. As the wing continues to close, the 
lower half, with its tightly plicated membrane, folds longitudi- 
nally beneath the coriaceous basal portion, so that the plications 
are completely encased, like leaves in a book, between a coria- 
ceous upper layer and the thinner membrane of an equal portion 
of the wing lying, when the wing is expanded, directly behind 
it; the apex of the wing, however, now lies in even @ worse 
position than before, directly beneath the root of the wing; ° 
would do so, but having by this last movement been turned up- 
side down, its elasticity allows another movement which its 7 
position before prevented ; and we now perceive the meaning ° 
the expansion and tenuity of the radiating veins in points E 
ranged in a circuit parallel to the outer border ; on the sae 
of the wing these are brought together, and it is just here tha 
the apex of the wing, which is apparently so much in the af 
now bends transversely downward beneath the remainder of z . 
wing, and the whole is reduced to less than a tenth, probably 
