Factors Influencing the Lifespan of Bees 235 



summer bee during the active season into a physiological 

 winter bee by preventing it from brood-rearing. 



Further indications of the interdependent effects of food, 

 care of brood, physiological condition and lifespan were 

 obtained from experiments carried out with bees separated 

 from their colony, and kept in cages or in small experimental 

 colonies. 



Lifespan and Physiological Condition of 

 Caged Bees 



In the experiments with caged bees attempts were made to 

 clarify the following questions: 



(a) What effect has pollen-feeding on caged bees and are 

 there any differences in the effects of pollen from various 

 plant species? 



(b) Which organs of the bee depend directly on the food- 

 composition? 



(c) Does a direct relationship exist between physiological 

 condition and lifespan? 



(d) Which substances in the pollen are decisive in the 

 activation of the physiological condition, and in the lifespan? 



The first investigations in this direction go back to the time 

 when Czech workers (Soudek, 1927; Hejtmanek, 1933, 1943; 

 Svoboda, 1940) observed that the pharyngeal glands of newly 

 emerged bees could be brought to full development by feeding 

 with pollen, soya flour and albumin. Subsequently, the present 

 author proved (1946, 1954) that pollen-feeding of caged bees 

 not only brought about an activation of the pharyngeal glands, 

 but also caused a building-up of the fat body, the development 

 of the ovaries, and a statistically proved longer lifespan. These 

 findings were confirmed by other workers (Back, 1956, 1959; 

 Bertholf, 1942; Beutler and Opfinger, 1949; Freudenstein, 

 1958; de Groot, 1953; Hess, 1942; Mussbichler, 1952; Pain, 

 1951a, b; Wahl, 1956), and it was also shown that pollen- 

 feeding produces development of the wax glands (Freuden- 

 stein, 1958). 



