148 



INTRODUCTION 



the hind-legs are thickly covered with hair from the tibia to the coxa. Even the 

 metathorax is sometimes provided with two well-developed tufts of hair, under which 

 considerable quantities of pollen can be accumulated (H. Miiller, 'Fertilisation/ p. 51). 

 Compared with the species of Sphecodes, those of Halictus and Anthrena have an 

 advantage in that their basal tarsal joints are considerably broader, and the tarsal 

 brushes are consequently more effective. These bees will therefore use exclusively 

 or chiefly as larval food the pollen that is collected by the hairy covering of the hind- 

 legs, whilst for the species of Sphecodes this method of collection is subsidiary. 



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Fig. 6o. Halictns and Anthreiia lafter Hermann Miiller). (i) Labium (lower lip) of Halictus 

 quadricinctus F. $ : iiii^ mentum (chin); //, ligula (tongue); pa, paraglossae (accessory tongues); //, 

 labial palp. (2) Right hindleg of the same bee. (3) Metathorax and right hind-leg of Anthrena ovina 

 KIg. 9 ; X, right tuft of hair on the metathorax. Other references in (2) and (3) as in Fig. 58. (4) Single 

 hairs from the body of an Anthrena ovina Klg. 9 , captured upon a flowering willow. To the feathery 

 branches of these hairs numerous pollen-grains are sticking. 



As in all the three above-named genera the entire body is hairy, it follows that 

 the bees in visiting numerous flowers cover themselves with pollen, which they 

 subsequently remove with the tarsal brushes, so that the quantity heaped up on the 

 special collecting-hairs is considerably augmented, especially as the hairs are mostly 

 feathery. In Sphecodes the hair-covering of the body is very scanty. Only the 

 legs are well covered, especially the outer sides of the posterior tibiae. The brushes 

 on the inner side of the basal tarsal joints are somewhat better developed than in the 

 genus Prosopis, a bee which is at the lowest stage of adaptation. The species of 

 the latter have an almost naked body, and the small basal tarsal joints possess but 

 a feebly- developed covering of hair. Pollen, however, often clings to these bees, 



