Pollination ecology of five hemiparasitic, large-flowered Rhinanthoideae with special reference to the pollination behaviour of nectar-thieving, shorttongued bumblebees

Operation of the pollination mechanisms of Rhinanthus serotinus (Schonh.) Oborny, R. minor L„ Pedicularis palustris L., P. sylvatica L„ and Melampyrum pratense L. by nectar and pollen-collecting bumblebees ( Bombus Latr.) was studied. Pollination by bumblebees may be achieved in two ways: 1. Head-thorax pollination by nototribic long-tongued bumblebees. Long-tongued bumblebees forage upright for nectar, while the stigma nototribically contacts residual pollen in the head-thorax crevice; pollen not retained in this crevice is groomed from the body by a forward movement of the middle legs crossed over the dorsum and deposited in the corbiculae. 2. Venter pollination by sternotribic, short-tongued bumblebees (inch nectar thieves). Nectar thieves obtain nectar by biting a hole in the long corolla tube close to the nectary. These short-tongued bumblebees usually collect pollen in an inverted position. They grasp the edge of the galea with their mandibles and tear it asunder. Their abdomen is curved under the pollen chamber formed by the galea enclosing the anthers. Pollen is vibrated loose by means of wing movements, which produce a hissing sound; pollen is deposited on the ventral side of the body of the bumblebee, particularly on the stemites and transported to the corbiculae. Both ways of pollen collecting result in deposit of large amounts of pollen on the bodies and in the corbiculae of the pollinating bumblebees.