Optimal timing of comb construction by honeybee (Apis mellifera) colonies:a dynamic programming model and experimental tests

Honeybee colonies, like organisms, should exhibit optimal design in their t emporal pattern of resource allocation to somatic structures. A vital colon y structure is the comb which stores honey for overwinter survival. However , the timing of comb construction poses a dilemma to a colony attempting to maximize its honey reserves, On the one hand, plenty of empty comb is need ed for efficient exploitation of temporally unpredictable flower blooms. On the other hand, because comb is made from energetically expensive wax, its construction too early or in excessive amounts will reduce the amount of h oney available for winter thermoregulation and brood-rearing. A dynamic opt imization model concludes that colonies should add new comb only when they have filled their old comb with food and brood above a threshold level. The threshold increases with time until, at the end of the season, building is never an optimal behavior, The temporal pattern of construction predicted by the model pulses of building coincident with periods of nectar intake an d comb fullness - matches that seen in an actual colony observed over the c ourse of an entire foraging season. When nectar sources are rich but tempor ally clumped, the model also predicts that bees should be sensitive to nect ar intake, employing much higher thresholds on days when nectar is not avai lable than on days when it is. Even under poorer and more dispersed nectar regimes, little fitness cost is paid by colonies replacing the optimal stra tegy with a simpler rule of thumb calling for new construction only when tw o conditions are met: (1) a fullness threshold has been exceeded, and (2) n ectar is currently being collected. Experiments demonstrate that colonies d o in fact use such a rule of thumb to control the onset of construction. Ho wever, once they have begun building, the bees continue as long as nectar c ollection persists, regardless of changes in comb fullness. Thus the onset and duration of comb-building bouts appear to be under partially independen t control.