JOINTED-LIMBED ANIMALS AS MESSMATES 175 



INSECTS (!NSECTA) AS MESSMATES. It will be convenient to 

 limit our attention to Bees and Ants, remembering that both 

 belong to an order (Hymenoptera Membrane- winged Insects) 

 of which the members are distinguished by an extraordinary 

 amount of specialization, associated with mental qualities of no 

 mean order. 



Bees as Messmates. Many species are known of what may 

 be called, for want of a better word, Lodger Bees (Psithyrus\ 

 each kind of which lives in the nest of some sort of Humble- Bee 

 (Bombus). In nearly all such cases the guest closely resembles 

 its entertainer in appearance, and the two dwell together in a 

 perfectly friendly way. The arrangement is of a one-sided nature, 

 for the lodger not only has free quarters, but also makes free use 

 of the provisions stored up by the industrious humble-bee, which, 

 however, is not directly harmed by the association. But as a 

 result of the raids made upon the larder by its lazy lodger, it is 

 not able to rear nearly so many young ones as would otherwise 

 be the case. A nest of a species of Humble- Bee (Bombus varia- 

 bilis), examined by H offer in early autumn, contained only a 

 queen and fifteen workers, together with eighteen Lodger- Bees 

 (Psithyrus campestris], of which eight were females. But for the 

 strain on the commissariat there would, it was estimated, have 

 been 200 humble-bees in the colony, or even more. 



Ants as Messmates. Occasion has already been taken to 

 note the curious relations which exist between Ants and Aphides, 

 the latter being fed and tended in return for their services as 

 "cows" (see p. 119). Even more extraordinary are the habits 

 of certain Slave-making Ants, which press other ants into their 

 service, employing them in all the varied duties of the nest. 

 The slavers conduct organized raids from time to time, in order 

 to keep up the number of their dependants, and it must be said 

 that these take very kindly to their enforced labours. A notable 

 European example is afforded by the large Amazon Ant (Poly- 

 ergus rufescens), which enslaves the small Brown Garden Ant 

 (Formica fusca). The following graphic account of the matter 

 is given by Newman (in An Introduction to the History of 

 Insects], and some of the details are set forth in fig. 1126: 

 " The most remarkable fact connected with the history of ants is 

 the propensity possessed by certain species to kidnap the workers 

 of other species, and compel them to labour for the benefit of the 



