G. it. Ent., 12 (54): 55-64
December 2007
Biologia di Xylocopa (Xylocopa) violacea (Linneo, 1758)
(Hymenoptera: Apidae):
studio preliminare sulla demografia
di
SALVATORE VICIDOMINI
Abstract - Biology of Xylocopa (Xylocopa) violacea (Linnaeus, 1758) (Hymenoptera: Apidae): preliminary study on the demography - To outline the main demographic traits of a southern Italian population of Xylocopa violacea (L.) is the aim of this contribution. Main results are as follows: a) The preferred nest substratum is the cut and dried A. donax cane, a recently acquired ethological character for X. violacea; b) The egg shows the highest mortality rate (7.48%), followed by the "non-defecating larva" (2.49%); c) 1/3 mortality not caused by predation-parasitism is due to individual deformation; d) Predator-parasite mortality (17.80% of cells = 18.11% of laid eggs; 23.66% of nests) is as follows: by conspecific females (7.96% of eggs), P. sicula (Lacertidae) (3.76%), C. scutellaris (Formicidae) (2.89%), S. cerambycina (Acari) (2.60%), P. pallidula (Formicidae) (0.58%); e) Mortality not due to predation-parasitism regards 19.53% of cells (18.07% of laid eggs); f) Conspecific females rob 8.1% of the pollen paste; g) Total mortality is 37.34% of cells (36.23% of laid eggs); h) In the study area, the main limiting factor to population growth is predation-parasitism, particularly intraspecific parasitism due to nest crowding; i) Population shows a density-dependent control and growth; j) Mortality is hardly affected by local ecological and climatic factors; k) X. violacea predators and parasites are occasional; l) There is a different preimaginal mortality between sexes (females are more vital).
