234 Anna Maurizio 



(maximum expectation of life 300-400 days — Anderson, 1931; 

 Farrar, 1949a; Lotmar, 1939; Maurizio, 1954). 



Many attempts have been made to explain these striking 

 differences between the lifespan of summer and winter bees. 

 The customary conception is that the lifespan is regulated, in 

 particular, by the collecting activity of the bee outside the 

 hive. According to this conception the bee works itself "to 

 death" on its collecting flights, when death is often caused by 

 accidents (Phillips, 1922, 1928). However, exacting experi- 

 ments have proved that where death is due to foraging the 

 shortening of life is only a matter of between four and eight 

 days, and thus is not long enough to explain the difference in 

 lifespan between summer and winter bees (El-Deeb, 1952; 

 Mauermayer, 1954). The genetically conditioned differences 

 in lifespan between bees of different races and cultivated 

 strains are also few. The bee is subject — like any other living 

 creature — to the process of physiological ageing, which is 

 based on the destruction of certain nerve cells. Rockstein 

 (1950a, 6, 1953) and Weyer (1931) estabhshed that in the 

 ageing bee the number of nerve cells in the olfactory lobe and 

 in the lower pharyngeal ganglion decreases by 35 per cent. 



Factors influencing the bees' lifespan become clear only 

 when one considers the behaviour of bees under experimental 

 conditions. For example, if one forces a young summer bee 

 in the nursing state to undertake continuous brood-rearing, 

 the pharyngeal glands will remain at their full development 

 for several weeks and thus increase its lifespan (Moskovljevic, 

 1939). This increase, as well as an enhancement of physio- 

 logical condition, accompanies the limitation of brood nests 

 in a colony ready to swarm. Particularly striking is the 

 behaviour of bees when put into a queenless or broodless 

 colony during the summer. Such bees not only possess for 

 several weeks fully developed pharyngeal glands, but also 

 form a winter fat body and thus become long-lived (maximum 

 life-span 166 days, as against 38 days in a colony with brood — 

 Maurizio, 1954). Therefore it is possible to transform a 



