ORGANIC ADAPTATION 



333 



son glands 



Levers to 

 move barb 



ter of the surface automatically determines whether claw or pul- 

 villus shall be used. But there is another adaptation equally re- 

 markable. "The pulvillus is carried folded in the middle, but 

 opens out when applied to a surface; for it has at its upper part 

 an elastic and curved rod, which straightens as the pulvillus is 

 pressed down. The flattened-out pulvillus thus holds strongly while 

 pulled along the surface by the weight of the Bee, but comes up 

 at once if lifted and rolled 

 off from its opposite sides, 

 just as we should pull a wet 

 postage stamp from an enve- 

 lope. The Bee, then, is held 

 securely till it attempts to 

 lift the leg, when it is freed 

 at once; and, by this exquisite 

 yet simple plan, it can fix 

 and release each foot at least 

 twenty times per second." 

 (Fig. 217.) 



The characteristic struc- 

 tures of the middle (meso- 

 thoracic) legs of the Bee are 

 a small pollen brush and a 

 long spine, or pollen spur. 



The METATHORACIC LEGS 



exhibit four remarkable 

 adaptations to the needs of 

 the insect, known as the 



POLLEN COMBS, PECTEN, 



auricle, and pollen basket. The pollen combs comprise a 

 series of rows of bristle-like hairs on the inner surface of the first 

 segment of the tarsus: the pecten is a series of spines on the distal 

 end of the tibia which is opposed by a concavity, the auricle, on 

 the proximal end of the tarsal segment; while the pollen basket 

 is formed by a depression on the outer surface of the tibia which 

 is arched over by rows of long curved bristles arising from its 

 edges. 



Thus the worker is fully equipped. Flying from flower to flower, 

 the Bee brushes against the anthers laden with pollen, some of 

 which adheres to the hairs on its body and legs. While still in 



Sheath 



Palpus of sting 



Barb 



Fig. 218. — Sting of a worker 

 Honey Bee. 



