i. 
1876.] How Cockroaches and Earwigs fold their Wings. 525 
reflexible portion of the reversible zone ; and ot, te the corre- 
sponding portions of the anterior zone. 
There are further modifications of this duplicature; thus in 
some types, the anal field being ample, a sim- p oo 
ple fan-like closure of the anal area is not ra oa 
sufficient, and its whole mass is again folded aena 
longitudinally and lies not only beneath the me e 
under surface of the anterior part of the wing, en wee 
on 
but beneath the reversible zone or anterior rs 
part of the anal area. This may readily be Fig. 37. 
seen on examining Figures 39 and 40 (cf. figures 36 and 37) in 
f which the diverging field r or qz is bent 
o > g Upon pq and lies beneath all the other folds 
of the wing. Add to this the reversal of 
peter the tip of the wing, and by a single stroke 
f v of the knife, one may cut through five lay- 
vee og ers of membrane, not counting the fan- 
like plications of the anal area which might be Pp c 
severed. g 
FA 
There is another curious fact; namely, that na 
; ? when the apical triangle has reached or near- 
— ly reached its maximum development, as in 
Prosoplecta coccinella (Figure 80) and Plectop- 
R tera porcellana (Figure 31), that portion of the 
n anal field which lies within the transverse fold, 
Baao T and above a line drawn from the socket of the 
PE, 1. wing to a point near the anal emargination (7, 
ey the basal portion of the reversible zone, b, b), assumes a vena- 
tion precisely analogous to that of the upper half of the wing with 
all its distinct cross-veins and odd reticulations; this becomes 
Possible because it is no longer folded with the rest of the anal 
field, and does not require simple longitudinal veins. When situ- 
ated above the anal emargination its relation to the anal area is 
almost entirely disguised. Even further than this : in some types, 
as in the Australian Diploptera silpha, the terminal reversed 
area, a simple development of the apical triangle, is filled with a 
het-work of secondary veins, wholly similar to those of the parts 
toward the base, and in some instances (but for the transverse 
fold) direct continuations of them; were the steps unknown by 
which Such a mode of wing-duplicature had been produced, and 
Ploptera silpha the sole living example of such duplicature, 
e structure of its wings would be utterly incomprehensible on 
