82 QUEEN-REARING IN ENGLAND. 



Casteel has lately pointed out that when the pollen grains 

 are small, and the whole mass in the corbicula is well 

 moistened, marks made by some of the corbicular bristles 

 will be seen on the sides of the load. These scratches are 

 transverse in direction, and show that the mass has been 

 increased by the addition of pollen pushed up from below.* 



The bumble-bee is the only bee besides the honey-bee 

 outside the tropics that possesses a corbicula, and she loads 

 it with pollen in essentially the same way as the honey-bee, 

 but the apparatus employed is less specialised. On refer- 

 ence to Fig. 41, it will be seen that the bristles comprising 

 the hind metatarsal brush are arranged, not in rows, but 

 irregularly, as in the solitary bees. The pollen paste is 

 found only in the corner of the brush nearest to the auricle, 

 which is the only part of the brush scraped by the coml>. 

 Only the upper end of the comb comes into contact with 

 the brush. The teeth at the lower end of the comb are, 

 in, fact, useless, being slender and hair-like (see Fig. 44), 

 whereas in the honey-bee every tooth is well formed (Fig. 45). 

 Indeed, the bumble-bee's comb shows very plainly that the 

 teeth of the comb in both bees are nothing more than 

 specialised hairs. In the bumble-bee the tips of the teeth 

 form a nearly straight line, but in the honey-bee they form 

 a convex curve, thereby making the comb an efficient instru- 

 ment for combing out the whole of the metatarsal brush. 

 The tibial spurs (Fig. 44, s, s) would impede the working 

 of so perfect a comb as that of the honey-bee and, though 

 present in all other bees, are absent in Apis and its tropical 

 allies, Trigona and Melipona. At the base of the comb in 

 each bee is a glabrous or naked area {g), which indicates 

 by its width what part of the comb is most used. 



In the honey-bee the working surface of the auricle is 

 covered with numerous small pointed teeth (6, Fig. 37) in- 

 clining in the direction that the pollen moves, but in the 

 bumble-bee the surface is smooth. 



The entrance to the corbicula, named by me the limen 

 (8, Fig. 37) is worth a moment's attention. In the bumble- 

 bee its edge is covered with short fluff consisting of fine 

 branched hairs. Further in stand about three stiff bristles 



* The Behaviour of the Honey-bee in Pollen Collecting, by D. B. 

 Casteel, Ph.D., U.S. Bureau of Entomology, Bulletin No 121, published 

 Dec. 31, 1912. 



