G. it. Ent., 7 (40): 339-344
August 31, 1995
Biologia di Xylocopa (Xylocopa) violacea (L., 1758)
(Hymenoptera: Apidae)
Foraggiamento su Lamium purpureum L. (Lamiaceae)
di
SALVATORE VICIDOMINI
Abstract - Biology of Xylocopa (Xylocopa) violacea (L., 1758) (Hymenoptera: Apidae). Foraging on Lamium purpureum L. (Lamiaceae) - The foraging ethology of Xylocopa violacea on Lamium purpureum is the aim of this contribution. L. purpureum is the main flower for the species to forage in January-February. Two foraging tactics have been recognized: nectar robbery ("R") and from corolla ("C"). These tactics are irreversible for males and reversible for females. The "R" tactic does not cause pollination and damage to the flower. The interocular hairy area is the pollen transporter. The foraging period is January-February for males and February-March for females. Foraging is highly progressive. Population efficiency is 10.5 flowers/min.; males and "R" individuals are more efficient than females and "C" individuals. Efficiency is higher in February than in March for females owing to the sexual harassment of March (main month for sexual interactions). Considerable individual differences in efficiency have been observed (5.00-37.17 flowers/min. for males; 2.39-18.00 for females). The mean time spent on a flower was 3.09 s., 3.29 s. with the "R" tactic, 3.03 s. with the "C" tactic; males spent 3.48 s. on a flower, females 2.65 s. Females spent more time in flight than males; the modal value for males is 3 s. (40.2%) on a flower, 2 s. (52.2%) for females. Males forage at t ≥ 8 °C, females at t ≥ 11 °C. "R" individuals spend more time on a flower than "C" individuals. The "R" tactic is so widespread in the Xylocopini probably because "R" individuals are more efficient (work hypothesis). Other visitors to Lamium purpureum are Apis mellifera, Bombus terrestris (Apidae) and Macroglossum stellatarum (Lepidoptera).
