230 SOCIAL LIFE IN THE INSECT WORLD 



Both dog and beetle are very near the subsoil which 

 they scrutinise ; the object they seek is at no great 

 depth. At a greater depth neither dog nor insect could 

 perceive such subtle effluvia, nor even the odour of 

 the truffle. To attract insect or animal at a great dis- 

 tance powerful odours are necessary, such as our 

 grosser senses can perceive. Then the exploiters of the 

 odorous substance hasten from afar off and from all 

 directions. 



If for purposes of study I require specimens of such 

 insects as dissect dead bodies I expose a dead mole 

 to the sunlight in a distant corner of my orchard. As 

 soon as the creature is swollen with the gases of putrefac- 

 tion, and the fur commences to fall from the greenish 

 skin, a host of insects arrive — Silphidae, Dermestes, 

 Horn-beetles, and Necrophori — of which not a single 

 specimen could ever be obtained in my garden or even 

 in the neighbourhood without the use of such a bait. 



They have been warned by the sense of smell, 

 although far away in all directions, while I myself can 

 escape from the stench by recoiling a few paces. In 

 comparison with their sense of smell mine is miserable ; 

 but in this case, both for me and for them, there is 

 really what our language calls an odour. 



I can do still better with the flower of the Serpent 

 Arum (Arum dracunculus), so noteworthy both for its 

 form and its incomparable stench. Imagine a wide 

 lanceolated blade of a vinous purple, some twenty inches 

 in length, which is twisted at the base into an ovoid 

 purse about the size of a hen's egg. Through the 

 opening of this capsule rises the central column, a long 

 club of a livid green, surrounded at the base by two 



