PHYSIOLOGY OF THE INVERTEBRATA. 



263 



discharge in unison, but after about twenty explosions they 

 only emit a white fluid. 



M. F. Pouchet * savs : — " L'instinct de la defense est telle- 

 ment inherent a la tribudes Bombardiers, qu'au seul coup de 

 canon d'alarme de I'un d'eux, tons les autres crcpitent en 

 meme temps : c'est un feu roulant sur toute la ligne." 



There is something in these insects discharging the fluid 

 in unison which seems to point out that they are guided not 

 merely by instinct, but by that which is the equivalent of mind. 



The chief enemy of B. crepitans, which inhabits Great 

 Britain, is Calosoma inq^mitor (Fig. 48). 



Fig. 48. — Bombardier Bef.tle and its Enemv. 

 {After F. A. Pouchet.) 



The secretory glands of the Bugs are situated exterior to 

 the insertion of the posterior legs, and emit foetid efiluvia on 

 seizure. 



The ground bettles of the genus Carahus, when disturbed, 

 eject a fluid which is caustic if applied to the skin. 



In conclusion, it may be remarked that a very large 

 number of insects eject liquids or vapours as a means of 



* L' Uuiters, p. 137. 



