SOCIAL LIFE 225 



distributed among the larvae by the females and that of the 

 salivary liquid which they receive in return." This com- 

 parison is made by Roubaud, who does not hesitate to 

 accuse the nurses of " actual exploitation of the larvae.'* 

 The males or " drones " in the nest though they bring no 

 food to the grubs take from them the sweet fluid (see 

 Fig. 59). Roubaud and Wheeler believe that the evolution 

 of the family society is to a great extent a result of the 

 reciprocal feeding ('* trophallaxis ") ; there " naturally 

 follows a tendency to increase the number of larvae to be 

 reared simultaneously in order at the same time to satisfy 

 the urgency of oviposition and to profit by the greater 

 abundance of the secretion of the larvae." 



The bees, which must now be considered, have, it is 

 calculated, only about 500 out of their 10,000 species living 

 in true social communities whereof specialised worker- 

 females form the great majority of members. The wasps 

 are predominantly predaceous, though many of them feed 

 on vegetable substances occasionally or habitually. The 

 bees, however, are as a group dependent on the products 

 of flowers — on the nectar which after digestion in the insects' 

 stomachs becomes honey, and on pollen ; the broad shin 

 and basal foot-segment and the feathered hairs of bees, 

 among the most striking of their structural features, are 

 connected with the habit of gathering pollen from the 

 floral anthers, while the tip of the labium is elongated to 

 form a beautifully efficient organ for licking up fluid from 

 the nectaries of blossoms. " SoUtary " bees, among which 

 no workers occur, provision their nests, as we have seen, 

 with honey and pollen, usually mixed to form " bee-bread," 

 partitioning the nest into chambers each of which contains 

 at first an egg, later a grub with its appropriate store of 

 food. In certain species of Halictus, which nest in burrows 

 in the ground, the mother closes up the chambers, but 

 guards the nest afterwards and survives till the development 

 of the young is complete ; there is, however, not time 

 enough for the realisation of social life between her and her 

 offspring. Wheeler quotes some very interesting recent 



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