24 6 
SYSTEMATIC ARRANGEMENT. 
with the body, and rubs them against each other with 
a brisk horizontal movement. The nervures on 
meeting each other produce the well known sound ; 
the areolets at the base seem to serve no other pur- 
pose than to give intensity to it. M. Burmeister, 
however, advances another explanation of the phe- 
nomenon in question. According to him, the air 
upon being forcibly expelled from the stigmata, par- 
ticularly those of the thorax, by the violent agitation 
which the animal imparts to its 'whole body, strikes 
against the lateral edges of the tegmina ; but being 
unable to escape in that direction, it is forced to as- 
cend, and comes in contact with the membranous 
areolets, which by being thus struck are thrown 
into a state of vibration. This may certainly con- 
tribute to the intensity of the sounds, but it is obvious 
from their nature, that they originate in a mechanical 
action rather than in the air issuing from the stigmata.* 
The field cricket (A. campestris ), presents a suf- 
ficient number of structural modifications, taken in 
connection with its mode of life, to justify the 
establishment of a separate genus for its reception. 
It is well known to reside in holes dug in the earth, 
where it lies in wait for insect prey. Although habit- 
ually carnivorous, it seems, however, capable of sub- 
sisting on vegetable substances ; for Stoll affirms that 
he kept a pair alive for a considerable time by feed- 
ing them on grass and crumbs of bread. Another 
interesting insect of this tribe is the mole cricket 
( GryUotalpa vulgaris) which has long attracted ob- 
Lacordaire’s Introd. i. p.275. 
