522 How Cochroaches and Earwigs fold their Wings. [September, 7 
This is a mode of duplicature common to all groups of Or- 
thoptera. But we have in cockroaches and earwigs something 
superadded, where the wing is large, and folded not only longi- 
tudinally but transversely, and is ingeniously packed away be- 
neath the shorter tegmina. We will follow Saussure in tracing 
among the cockroaches the various steps from the simple to the 
complex form. 
As usual among insects, the anal field of the hind wing in 
cockroaches (Figure 29, r 1) does not generally extend much more 
than half way toward the tip 
of the wing; and, as in most 
insects, especially those of low 
organization, the upper limit of 
this area (that separating it 
from the principal part of the 
ne wing, Figure 29, p) is marked at 
the edge of the wing by a slight emargination. The first step 
toward the result to be attained is the lengthening of the anal 
field so that it equals the anterior parts, bringing the indentation 
to the apex of the wing. This is seen in Thorax porcellana of 
the East Indies. There is, however, a little triangular bit of 
membrane left between this indentation and the lowermost 
nervule of the next vein above. It is to this little triangle that 
we must direct our attention. For in the next stage, such as 18 
seen in a common European cockroach, Hetobia lapponica, this 
triangle has greatly enlarged ; the principal longitudinal fold of 
the wing, that separating the anal area from the parts a ve, 18 4 
obliged to run directly through the middle of this triangle, 50 a 
that we may fairly consider one half as belonging to the oy 3 
and the other half to the median field of the wing. Since, how- 
ever, it contains in itself no nervures and has become also da G 
more or less coriaceous texture, its posterior portion cannot oT = 
part in the plications of the anal field ; moreover, it has expand a 
apically and now forms the entire tip of the wing, producing 3 
its upper limit a slight excision of the edge similar to the norm : 
emargination at its lower limit. When the anal fel 
closed and lies at rest beneath the anterior part of the wing, t a 
triangle, reduced to half its size by a single fold, lies bey ond ae 
edge of the wing, and either folds back again upon the uppe 
surface of the wing or curls up in the same position and 18 Wi 
Dr, de Saussure for tbe DR 
Seay. hres 
1 Figures 29-40 have been generously forwarded by 
tration of this paper. 
