Fabiana Oliveira da Silva

Does forest loss affect the communities of trap-nesting wasps (Hymenoptera: Aculeata) in forests? Landscape vs. local habitat conditions

We investigated changes in the communities of trap-nesting Hymenoptera in forests in relation to forest loss on a landscape scale and understory conditions on a local habitat scale. Two specific questions were addressed. (1) Do the communities change with degrees of forest loss? (2) Do the communities change with varying local environmental conditions of understory habitats? The study was made in a landscape characterized by distributed forest patches within intensively managed agricultural surroundings. We deployed trap-nests at eight randomly selected sites in forests in summer. To quantify forest loss, the amount of forest coverage was calculated using GIS. To indicate local habitat conditions, the species richness of understory flowering plants was used. All together, 12 species of wasps and no bees were captured. Regression analyses showed that both abundance and species richness of the wasps were not significantly related to forest coverage. However, abundance of trap-nesting wasps was significantly related to species richness of understory plants, but species richness of the wasps was not significantly related to the plants. These results suggest that communities of trap-nesting wasps in forests are influenced more by the local habitat conditions than by forest loss.

Artificial covering on trap nests improves the colonization of trap-nesting wasps

To evaluate the role that a trap‐nest cover might have on sampling methodologies, the abundance of each species of trap‐nesting Hymenoptera and the parasitism rate in a Canadian forest were compared between artificially covered and uncovered traps. Of trap tubes exposed at eight forest sites in six trap‐nest boxes, 531 trap tubes were occupied and 1216 individuals of 12 wasp species of four predatory families, Vespidae (Eumeninae), Crabronidae, Sphecidae and Pompilidae emerged over 2 years, and no bee species were found. Results indicated that artificial covering led to a significant increase in the number of nested tubes of Ancistrocerus adiabatus, Ancistrocerus antilope, Ancistrocerus campestris and Auplopus mellipes, and significant effects of covering were not found for the other species. No significant difference in the overall parasitism rate between covered and uncovered traps was noted. These suggested that the covering technique could provide more opportunities for some wasp species to colonize trap nests.

Distribuição de Ninhos de Abelhas Xylocopa (Hymenoptera: Apidae) em uma Area de Dunas Litorâneas

The spatial distribution, density and the types of the substrates used by Xylocopa (Megaxylocopa) frontalis Olivier, X. (Schoenherria) subcyanea Perez and X. (Neoxylocopa) cearensis Ducke, in a sea coastal sand dune, in Bahia, Brazil, were determined. Both the substrate available and those effectively used by the bees for nesting have a clumped spatial distribution. The distribution of the nesting sites could be related to the clumped spatial distribution of the available substrates. The highest occurrence of nests was found of a living individual of Agaristha revoluta (Spr.) DC, which was the substrate predominantly available. The density of available substrates and the density of nesting sites were 12.4/ha and 4.4/ha, respectively.