328 FOUNDATIONS OF BIOLOGY 



with a pair of notched CLAWS, a sticky pad (PULVILLUS) 

 and TACTILE HAIRS. (Fig. 178.) When the Bee is walking 

 up a rough surface, the points of the claws catch and the 

 pulvillus does not touch, but when the surface is smooth, 

 so that the claws do not grip, they are drawn beneath the 

 foot. This change of position applies the pulvillus, and it 

 clings to the smooth surface. Thus the character of the 

 surface automatically determines whether claw or pul- 

 villus shall be used. But there is another adaptation equally 



FIG. 178. Foot of the Honey Bee in the act of climbing, showing the 'automatic' 

 action of the pulvillus. A, position of foot on a slippery surface, fh, tactile hairs; pv, 

 pulvillus; t, last segment of tarsus; a n, claw. B, position of foot in climbing on a rough 

 surface, an, c, claw. C, section of a pulvillus just touching a flat surface; cr, curved 

 rod. D, the same applied to the surface. (From Packard, after Cheshire.) 



remarkable. "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 envelope. 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." 

 (Cheshire.) 



The characteristic structures of the middle (MESOTHORACIC) 

 legs of the Bee are a small POLLEN BRUSH and a long spine, or 



