396 NOISES OF INSECTS. 
back. In the female both these portions resemble each 
other in their nervures; which running obliquely in two 
directions, by their intersection form numerous small 
lozenge-shaped or rhomboidal meshes or areolets. ‘The 
elytra also of these have no elevation at their base. In 
the males the vertical portion does not materially differ 
from that of the females; but in the horizontal the base 
of each elytrum is elevated so as to form a cavity under- 
neath, The nervures also, which are stronger and more 
prominent, run here and there very irregularly with 
various inflexions, describing curves, spirals, and other 
figures difficult and tedious to describe, and producing a 
variety of areolets of different size and shape, but generally 
larger than those of the female: particularly towards the 
extremity of the wing you may observe a space nearly 
circular, surrounded by one nervure, and divided into 
two areolets by another?. The friction of the nervures 
of the upper or convex surface of the base of the left-hand 
elytrum—which is the undermost—against those of the 
lower or concave surface of the base of the right-hand— 
which is the uppermost one—will communicate vibrations 
to the areas of membrane, more or less intense in propor- 
tion to the rapidity of the friction, and thus produce the 
sound for which these creatures are noted. 
The merry inhabitant of our dwellings, the house- 
cricket (Acheta domestica, F.), though it is often heard 
by day, is most noisy in the night. As soon as it grows 
dusk, their shrill note increases till it becomes quite an 
annoyance, and interrupts conversation. When the male 
sings, he elevates the elytra so as to form an acute 
* Compare De Geer, iii. 512. 
