636 EXTERNAL ANATOMY OF INSECTS. 
of some quadrupeds*. It is to be observed that in the 
secondary folds of these wings the angles of the folds are 
surmounted by a nervure. 
In both sections of the Hemiptera Order, as in the Co- 
leoptera, the Anal Area is turned under the wing and lies 
over the back of the insect ; this is the only primary fold, 
but besides there are several longitudinal semifolds or 
secondary ones, in which one part of the surface forms an 
obtuse angle with another; and in Cicada, &c., these 
folds ramify in the wings as well as in the ¢egmina at the 
margin: a number of semifolds also, sometimes trans- 
verse and sometimes oblique, run in pairs from each side 
of every nervure of the disk of both zegmina and wings 
in the genus last named, the use of which has been be- 
fore mentioned >. 
We now come to those Orders that have four mem- 
branous wings: first, I shall consider the Lepidoptera. 
With respect to the position of their wings in repose some 
variations take place. In the majority of the day-fliers 
(Papilio L.), when the animal reposes the wings are ap- 
plied to each other by their upper surface so as to be 
vertical ; but in the skippers (Hesperia), the secondary 
wings assume a horizontal position, while the primary are 
vertical but applied to each other. In the Crepuscular 
tribes (Sphinx L.) the upper wings are incumbent on the 
lower, and deflexed. In the night-fliers (Phalena L.) 
the types of position are various. In some (Aétacus, Sa- 
turnia, the Noctuide, &c.,) the wings cover each other, 
and are a little inclined from a_ horizontal position; in 
Gastropacha, Odenestis, and some other Bombycida, they 
are deflexed, and the anterior margin of the under wing 
4 Stoll Grillons, t.1. c.f. 1, 2. » See above, p. 634. 
