250 



THE BIOLOGY OF INSECTS 



two kinds of insect is mutually beneficial. Ants that use 

 aphids in this way, as " cattle," never devour or attack them ; 

 they rather protect them and drive off threatening enemies 

 or carry away the aphids to some safe refuge. The aphids, 

 on their side, never try " to escape from the ants . . . but 

 accept the presence of these attendants as a matter of 

 course." A. Mordwilko (1907) states that in some aphids 

 habitually associated with ants, there is a ring of stiff hairs 

 surrounding the vent ; these hairs hold the drop of honey- 

 dew until the feeding ant has swallowed it, so that they 

 appear to be related rather to the latter than to the aphid 

 itself. 



Among the most remarkable of all ant-guests are various 

 kinds of beetles that spend their 

 whole lives in ants' nests. They 

 belong to several distinct families, 

 such as Staphylinidae or rove- 

 beetles and their allies the Psela- 

 phidae (Fig. 63), as well as the 

 curious Paussidae. Wasmann has 

 described and discussed at length 

 the relations between the ants and 

 these guest-beetles which are fre- 

 quently reddish in colour, their 

 bodies adorned with tufts of 

 yellow hairs surrounding the 

 openings of glands which secrete 

 an aromatic volatile fluid licked 

 The beetles are themselves fed by the 

 liquid ; the guests solicit this by 



Fig. 63. — Pselaphid Beetle 

 (Claviger testaceus) a 

 * ' guest " of the British 

 and European Yellow Ant 

 (Lasius flavus). X 12. 



up by the ants, 

 ants on disgorged 

 stroking with their feelers or fore-legs the heads of their 

 hosts. Their jaws are often modified for the reception of 

 this liquid food, so different from the solid nutriment 

 devoured by the vast majority of beetles. Not the adult 

 beetles only but their grubs also live in the ants' nests, 

 where they are tended and fed by the workers, though they 

 have often been observed to attack and devour the ant 

 larvae, It has not unnaturally been suggested that the ants 



