G. it. Ent., 11 (52): 91-98
December 2004
Biologia di Xylocopa (Xylocopa) violacea (Linneo, 1758)
(Hymenoptera: Apidae):
foraggiamento su Vicia faba L. (Leguminosae: Vicieae)
di
SALVATORE VICIDOMINI
Abstract - Biology of Xylocopa (Xylocopa) violacea (Linnaeus, 1758) (Hymenoptera: Apidae): foraging behaviour on Vicia faba L. (Leguminosae: Vicieae) - The aim of this contribution is to study the foraging ethology of Xylocopa violacea on Vicia faba. Two foraging tactics have been observed: from the corolla, with flower pollination (3.4% of flowers), and nectar robbery, without flower pollination and damage to the flower (96.6%). Female visit less flowers/min. than males and spend longer time on a flower than males; males visit a double number of flowers/min. in January than in March; they spend longer time on a flower in March than in January and more s/min. (+48%) in flight in March than in January. These data come from the male mating behaviour in this area: the random search for females in flight on V. faba in February-April. A number of advantages come from the robbery tactic, among them, a higher number of flowers/min. visited than with the corolla tactic, as recorded for Lamium purpureum. The robbery tactic among the Xylocopini is probably so widespread for the following hypothesis: the nectar robbery tactic, with or without pollination, allows a higher number of flowers visited per min. than the corolla tactic, with increased energetic reward. X. violacea is a very inefficient pollinator of V. faba. Other V. faba visitors are: Macroglossum stellatarum and Pieris brassicae (Lepidoptera), Epicometis hirta and Oxythyrea funesta (Coleoptera), Anthophora acervorum, Apis mellifera, Bombus terrestris, Eucera longicornis, Xylocopa iris and 3 other undetermined species of Apidae. Other plant species on which X. violacea uses the robbery tactic are: Antirrhinum majus, Canna indica, Cordia mixa, Linaria vulgaris, Mirabilis jalapa, Symphytum tuberosum, Trapeolum lobbianum, Salvia eriocalyx, S. menthaefolia, S. mexicana, Saponaria officinalis, Petunia hybrida, Corydalis sp., Fumaria sp., Jasminum nudiflorum, Lonicera etrusca, Petrocoptis grandiflora, Narcissus cantabricus, N. tazetta, Vicia sativa. It is supposed that X. violacea feeds also on the pollen of V. faba.
