Pollination activity by blowflies and honeybees on onions in breeders' cages

Abstract

SUMMARYHoneybees (Apis mellifera) and three species of blowflies (Calliphora vomitoria, Lucilia caesar and L. sericata) were observed on mass‐pollinated populations of onions (Allium cepa) in 4·4 × 3·6 m × 2‐2·5 m cages in June‐August 1977. Pollination activity at temperatures from 14° to 28°C was compared on the basis of mean time per flower touched on each umbel visit.Honeybees did not forage below 16°C. Above 16°C their mean time per flower was short (1·4 s) and varied little with temperature. For blowflies, it decreased markedly from 12·1 s at 14–15·5°C to 2·7 s at 26°C and above, largely because at low temperatures flies spent long periods quiescent or grooming rather than actively feeding.When flowering was not completely synchronous between cultivars, honeybees were more selective than blowflies, but where flowering was synchronous, both types of pollinator visited the two cultivars at random.For the size of cage used, neither type of insect had a distinct advantage as a pollinator of onions, despite their different behaviour patterns.