WING OF CRICKET. 95 



knowledge of Plies, consult ' Walker's British Diptera/ 

 vol. iii ; ' The Insecta Britannica/ 



WING OF COLEOPTERA. 



Beetles have four wings ; but the upper pair, being crusta- 

 ceous and used only as a protection for the under pair, are 

 called Elytra. Their use is obvious from the habits of the 

 Coleoptera ; they burrow in the ground arid reside under 

 the bark of trees, or beneath stones, when the undefended 

 membranous wing would receive the greatest injury. The 

 under wing is particularly described when examining the 

 slide of Telephorus. 



Both of these should be mounted and observed. The 

 upper pair, or Elytra, if properly prepared, are very beau- 

 tiful polariscope objects, especially those of Dytiscus and 

 Cockchafer (Melolontha) . 



But there is a more important notice to be taken of the 

 internal structure of the Elytron. Dr. Hicks discovered 

 the same vesicles here as he did in the antennae of Flies 

 and Bees. (See Antennse.) The wing-nerve branches 

 over the Elytron, and those dots which exhibit the black 

 cross with polarized light, are vesicles or organs of sensa- 

 tion, to which a distinct branch of the nerve may be 

 traced. 



Soak the Elytron in potash for a week or more, and when 

 perfectly transparent mount in balsam. 



The under wings exhibit groups of these vesicles on the 

 under side of the sub-costal nerve, as many as 200 and 300 

 in each wing. Observe the wing of Strangalia, a Longi- 

 corne Beetle. (See 'Journal of Linnean Society/ vol. 

 i, p. 136, Nov. 1, 1856). See also Elytra of Diamond 

 Beetle. 



WING OF CRICKET. 

 (AcJieta domestica.) 



This is mounted to show the organ of sound, the drum 

 and file by which the male Cricket chirps. Each of the 

 upper wings, or Elytra, has a round transparent space called 

 the drum, or tympanum ; at the base of each Elytron is a 



