44 THE CAUSES WHICH PKOPAGATE 



excretory ducts opening into erectile anal tubes, sometimes 

 vaporising with explosion. The Bombardier Beetles, according 

 to Leon Dufour, conceal themselves beneath stones, and when 

 disturbed launch from the anus a white pungent smoke re- 

 sembling nitric acid in its properties. Brachiaus disjjlosor (Duf.), 

 common on Spanish highlands, will furnish twelve such discharges, 

 but subsequently explosion with noise is replaced by the emission 

 of a yellowish or brownish fluid which gives out bubbles of air as 

 if it fermented. The mobility of the posterior abdominal rings 

 which are not covered by the elytra allows this coleopteron to 

 bend its abdomen to the point of irritation, whether below or 

 above; in the latter ease the elytra after the explosion become 

 sprinkled with sulphurous dust. This phenomenon is seen in 

 either sex. Our native species [B. crepitans) is sometimes 

 gregarious, and then when one individual is disturbed the whole 

 discharge in unison; but after a few puffs, twenty according to 

 Roesel and Rolander, they only emit a white fluid. Its chief 

 enemy is the handsome Calosoma inquisitor^ Rennie tells us, 

 which hunts it without mercy. " As it finds it impossible to 

 escape by speed of foot, it stops short and awaits its pursuer ; 

 but just as he is about to seize it, he is saluted with a dis- 

 charge.''' The fugitive beetle and pursuer are portrayed on 

 Plate I., Fig. 6. 



The odour diffused by the little nimble beetles of the genus 

 Pterostic/ius, so common near damp walls, well-mouths, and 

 refuse heaps, flavours of vinegar, smelling-salts, or pyroligneous 

 acid; and in the small and brassy Loricera pilicornis, the 

 smelling-salt flavour is even more pronounced. The tree-beetles 

 Calosoma and foreign species of Callidium have a scent of 

 ratafia. The secretions may likewise be disagreeable to our senses, 

 as in Cychrus, or they are perfumes pleasant and musky, as we 

 find them in the meadow Tiger Beetles, of which a sort [Cincindela 

 metallica, Bois.) found in New Ireland adds a balmy fragrance 

 to the warm air as it flies. The larger ground beetles of the 

 genus Carabus, when handled, eject a saliva which is burning 

 and caustic if applied to the cheek and tenderer portions of 

 the skin. With the beetles with short wingcases, the ejection 

 of the scent from its reservoirs is accomplished by reversion 

 of the abdomen (Plate I., Fig. 9) ; and in a small species of 



