PHYSIOLOGY OF THE INVERTEBRATA. 



263 



discharge in unison, but after about twenty explosions they 

 only emit a white fluid. 



M. P. Pouchet * says : — " L'instinct de la dtfense est telle- 

 ment inherent h, la tribu des Bombardiers, qu'au seul coup de 

 canon d'alarme de I'un d'eux, tous les autres crdpitent en 

 mSme 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 inquisitor (Fig. 48). 



Fig. 48. — Bombardier Beetle and its Enemy. 

 (^J/ier F. A. PouCHET.) 



The secretory glands of "the Bugs are situated exterior to 

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

 seizure. 



The ground bettles of the genus Carabus, 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' Univers, p. 137. 



