238 AN INTRODUCTION TO ZOOLOGY 



in this basketlike structure, it is possible for the bee to spend more 

 time in the field, and to carry a larger load at each trip. The 

 pollen basket in cross section is shown in Figure 131, G. The 

 pollen combs (at p in B) serve to fill the baskets by combing out 

 the pollen, which has become entangled in the hairs on the thorax, 

 and transferring it to the concavity in the tibia of the opposite 

 leg. At the distal end of the tibia is a row of wide spines; these 

 are opposed by a smooth plate on the proximal end of the meta- 

 tarsus. The term wax pinchers (wp. in B) has been applied to 

 these structures, since they are used to remove the wax plates 

 from the abdomen of the worker. 



WALKING. In walking three legs are extended at one time, 

 the other three supporting the body like a tripod. The foreleg 

 pulls the body forward, the middle leg maintains equilibrium, 

 and the hind leg pushes the insect forward. The details of walk- 

 ing in insects are very complicated. 



WINGS. Each of the first two thoracic segments bears a pair 

 of membranous wings. When at rest the wings He horizontally 

 over the abdomen, but when flying are widely spread. The wings 

 may be described as transparent membranes supported by hollow 

 ribs called nerves or veins. The pair of wings on one side of the 

 body may be joined together by a row of hooklels on the anterior 

 margin of the hind wing, w r hich are inserted into a troughlike fold 

 in the posterior margin of the fore wing. 



FLIGHT. When flying the wings act as inclined planes, and 

 locomotion forward is attained by both up and down strokes, 

 the tips of the wings moving in a curve shaped like a figure 8. 

 Motion backward, or a sudden stop, may be accomplished by 

 changing the inclination of the plane of oscillation. 



THE ABDOMEN AND ITS APPENDAGE. The abdomen is made up 

 of a series of six visible segments or rings of chitin inclosing a large 

 part of the alimentary canal, nervous system, reproductive organs, 

 etc. Each ring has a dorsal plate, the tergum, and a ventral plate, 

 the sternum. Thin chitinous membranes connect the rings, and 

 make the movement and expansion of the abdomen possible. 



