Yamada, T.; Yamada, Y.

We proposed a mathematical model that can estimate the apparent longevity of bees using only both the number of adults and capped brood. Seasonal changes in apparent-longevity estimated using field experimental data provide the following interesting findings: The apparent longevity of mite-free and pesticide-free bee colonies is almost constant after wintering until mid-September, then begins to increase from late September, continues to increase until the end of wintering, reaching a maximum just before the end of wintering, and eventually drops sharply to a low level after the end of wintering. Such normal seasonal changes in apparent longevity were confirmed also in mite-free colonies which ingested sugar syrup (SS) with pesticides and pollen paste (PP) without pesticides. The above results that the longevity of adult bees begins to increase from late September and the fact that worker bees become adult bees on the 21st day after the oviposition of the queen suggest the need to prevent exposure to bee swarms to mites and pesticides from early September as a measure to prevent failure of wintering of bee colonies. On the other hand, mite-free colonies which ingested neonicotinoid-containing PP and mite-infested colonies, show abnormal seasonal changes in apparent-longevity that cannot increase since late September towards the end of winter, as if the bees are not aware of the approach of winter. Due to the fact that pollen is the main food of bee brood (larvae and pupa), that mites parasitize on brood, that neonicotinoids maintain their toxicity for a long time, and that important functions and organs of bees are created during the larval and pupa periods, it is presumed that such abnormal seasonal changes in apparent longevity make it impossible for bees to notice that winter is approaching because biological rhythms are disturbed by damage by neonicotinoid-containing PP and parasitic mites.