642 EXTERNAL ANATOMY OF INSECTS. 
ing Orders, hairs or scales are more or less implanted in 
these organs: as the Lepidoptera are the most remarka- 
ble for the clothing of their wings, I shall leave them till 
the last, and begin with the Neuroptera. If you lightly 
pass your finger over the wing of any dragon-fly (Libel- 
lulina), from the apex towards the base, you will find 
that the longitudinal nervures are, as it were, serrulated 
with very minute bristles, which point towards the ex- 
tremity; if you next move the finger across the wing, 
from the posterior to the anterior margin, a similar cir- 
cumstance will strike you. M. Chabrier conjectures 
that, amongst other uses*, these hairs may contribute to 
fix the atmospheric fluid when the wings are depressed 
in flight, while it glides over them as they rise? ; in As- 
calaphus, Myrineleon, Nemoptera, Hemerobius, &c., the 
nervures are more visibly bristled ; the bristles diverging 
on each side from the longitudinal ones, but all pointing 
towards the apex from the connecting or transverse ones; 
in Panorpa, besides these bristles, short hairs, pointing 
the same way, are thickly planted in the membrane of 
the wing ; and in Hemerobius the margins of the wing are 
fringed; in the Ephemerina, Corydalis, &c., the wings 
are naked. In the Trichoptera Order, as their name 
imports, they are covered with minute decumbent hairs, 
less easily seen but still existing in the secondary pair. 
In the Hymenoptera in general the wings are covered 
with minute hairs or bristles; but in Tiphia, Scolia— 
with the exception of S. Radula and affinities in which 
they are hairy—and others, the wings are nearly naked ; 
@ For some uses of hairs, see above, p. 398—. 
> Analyse, 24. He seems to think that certain crooked hairs, in 
some wings, supply the place of folds. bid. 
