592 _ EXTERNAL ANATOMY OF INSECTS. 
there are never more than ¢wo wings, and one instance 
is known in which an insect of this Order has none * 
Certain genera or individuals of the Tetrapterous Orders 
are also furnished with alule: besides Dytiscus, Blatta, 
Lobophora hexaptera, which have been before noticed °, 
they may be detected in miniature in Ammophila and 
affinities ; these all may be regarded in some slight de- 
gree as insects with szx wings. 
ii. Kinds. Under this head we may consider the or- 
gans of flight as to their sztwatzon and as to their sub- 
stance. As to their situation, usually the first pair are 
attached to the mesothorax, and the second to the meta- 
thorax ; but in one instance, as has been before ob- 
served °, in the Strepszptera the anterior pair belong to 
the manitrunk, and the posterior to the mesothorax. As 
to their substance, they take the several denominations 
of elytra, tegmina, hemelytra, and wings, for the most 
part according to its variations, as will be seen more at 
large hereafter. Under this head I shall only further 
observe, that in many instances the organs of flight ap- 
pear to be mere abortions or rudiments, which serve to 
exemplify what has been more than once stated, that the 
CREATOR has seen it good to approach to new organs 
gradually as well as to new forms. Thus elytra are mere 
rudiments that do not serve to protect the wings in 
Atractocerus ; tegmina in some species of Phasma, Acry- 
dium, &c.; hemelytra in the bed-bug*; wings in many 
* Chionea araneoides Dalm. 
» See above, p. 557—. and Vot. II. 343, 348—. 
° See above, p. 591, Note c. 
* De Geer, iii. ¢. xvii. f. 10, 11. ff. M.Savigny has noticed a part 
in some Annelides, which he regards as analogous to elytra. Systeme 
des Annelides, 4, 9, 11. 
