II 



LIFE-HISTORY OF BOMBUS .43 



The underground pocket-makers, namely, ruder- 

 atus, kortorum, and latreillellus, and probably also 

 distinguendus, a close relation of latreillellus, prime 

 their egg-cells with pollen, placing a little pollen in 

 the bottom of each egg-cell constructed, and laying 

 their eggs upon it, and thus they preserve another 

 trace of the primitive feeding-method of the solitary 

 bees. These four species form a natural group, 

 which I propose to call "pollen-primers." They are 

 all large, with long heads and long tongues. 



The pocket-makers, at least B. ruderatus, der- 

 hamellus, agrorum, and heifer anus, make, as a rule, 

 only one pollen-pocket for each bunch of larvae, but, 

 under certain conditions, they may make two or 

 three. When many larvae are being reared by a 

 small staff of workers, the pockets are small, and 

 the pollen that is placed in them is plastered on to 

 the wall covering the larvae, from which it quickly 

 disappears, being no doubt consumed almost im- 

 mediately ; but when the population is greater, and 

 the weather being fine, pollen is gathered in plenty, 

 the pockets are large and cup-shaped, and contain 

 during the day a shallow store of pollen, the surface 

 of which is concave. In a nest of derka?nellus that 

 I took on July 2, 191 1, in the height of prosperity, 

 the pollen-pockets or cups were very large and of 

 an oval shape, several of them measuring in. 

 long by J in. wide ; they were, however, quite 

 shallow, the depth of the pollen in them at the 

 centre being only about |- in., and there was 

 only one pocket to each bunch of larvae. When 



