Some workers seem to be of the opinion that the increase in day length after the winter solstice triggers the onset of brood rearing (Avitabile, 1978). However, this hypothesis is not able to explain why there is brood rearing in colonies kept in complete darkness in freezing rooms, why there is such great variation in the time of brood rearing commencement, or why there are frequent stops in brood rearing in late winter. -- STIG W. OMHOLT


> The photoperiod was artificially shortened for free-flying honeybee colonies in May, June and July in order to simulate day-lengths of October, November and December. The effects on population development and on worker physiology were examined. There was no significant effect on numbers of brood cells or adult bees, or on the dry weight of the hypopharyngeal glands. The survival rates of workers did not increase significantly. On the other hand, the shortening of the photoperiod led to a winter-bee-like increase of the lipid and protein content of the fat body. However, the "short-day" treatment was not enough to trigger the development of long-living winter bees. 

Effects of artificial shortening of the photoperiod on honeybee (Apis mellifera ) polyethism. 
Fluri, P | Bogdanov, S  Journal of Apicultural Research [J. APIC. RES.]. Vol. 26, no. 2, pp. 83-89. 1987. 

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