204 ORGANISMS ILLUSTRATING BIOLOGICAL PRINCIPLES 



motion although the entire labium aids in the process. While feed- 

 ing, the flap of the labrum or epipharynx is lowered, making a pas- 

 sageway for the nectar to pass into the mouth. Thus the mouth 

 parts, which are all present in the locust as separate structures, 



here form a sort of pro- 

 boscis, that when not in 

 use is folded back under- 

 neath the head. 



Bees also feed on solids 

 such as pollen and "bee 

 sugar," which they mois- 

 ten with regurgitated 

 honey and saliva before 

 swallowing. The mandi- 

 bles and maxillae are both 

 used in feeding on solids, 

 but the chief uses of the 

 mandibles are in building 

 honeycomb. 



Bees are well provided 

 with sensory structures. 

 Experiments by Mclndoo 

 and Von Frisch indicate 

 that bees can distinguish 

 between different-tasting 

 substances, for some of 

 which they show strong 

 preferences. But whether 

 they can actually taste or 

 whether they distinguish substances by means of a sense of smell 

 is difficult to prove. Several experiments have been made that 

 prove the presence of a well-developed perception of odor. Among 

 the most convincing experiments were those in which Von Frisch 

 trained bees to select certain odors, such as oil of orange peel, out 

 of 43 other odors. He concludes that not only can bees discover 

 feeding places through a sense of smell but they tell other bees of the 

 existence of food supplies by means of a "round dance" in which the 

 successful bee probably holds the odor of the particular flowers on 

 which she has been feeding and disseminates it to the bees that crowd 

 around her in the hive. 



Wright Pierce 



Head of worker bee. Anterior view. Com- 

 pare this with the accompanying hne drawing 

 and identify as many structures as you can. 



