246 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 a^r 

 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 

 {Gryllotalpa vulgaris) which has long attracted ob- 



* Ltcordaire's Introd. i. p. 275. 



