THE SOCIAL INSECTS 



important, the schedule can be widely modified to suit the 

 needs of the colony. After swarming, for instance, there 

 may be an unusually low proportion of the older workers 

 and the foraging may then be done by much younger bees. 

 Such a result can easily be demonstrated experimentally by 

 making up a colony in which all the workers are of about 

 the same age. 



The key function is that performed between the sixth and 

 fourteenth days, for this is the time when the workers are 

 producing the royal jelly. This is a secretion of the pharyn- 

 geal glands which is passed into the alimentary canal just 

 inside the mouth. This liquid, on ejection from the mouth 

 into the cells, thickens into a pale jelly-like paste. Glands of 

 the same type are found in all bees and wasps, but their 

 function in other species has not been demonstrated. In the 

 honey bee, the glands become active on about the sixth day 

 and shrink and cease to secrete on the fourteenth, so that this 

 age-group of workers is essential for brood-rearing. Appar- 

 ently, the development of the gland can be a little hurried up 

 in emergencies, and it is said that it may become functional 

 a second time if older workers receive a diet rich in proteins. 



The existence of a schedule of duties which is capable of 

 modification for changing circumstances is characteristic 

 of the social organisation of bees, but we have no idea, as 

 yet, how this result is attained. 



THE LANGUAGE AND DANCES OF BEES 



The most remarkable advance in our knowledge of honey 

 bees is due to von Frisch's discovery of what he has termed 

 " the language " of bees. The first part of this work was 

 published in 1923, but von Frisch largely dropped the investi- 

 gation for twenty years. It was taken up again in Austria 

 during the Second World War and led to discoveries so 



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