Nesting and Biology of Alastor mocsaryi (Hymenoptera, Vespidae: Eumeninae)

Abstract

The nest structure of Alastor mocsaryi in trap nests was studied in Crimea. Fifteen nests were examined, located inside hollow reed stems 3.0–4.8 mm in inner diameter. The nests contained 1–9 cells separated by partitions. These were made of gravel cemented with soil mastic or sand. The bottom partitions (present in 14 nests) and final plugs (present in 2 nests) also contained loose gravel particles. The mean cell length was greater in the nests made in narrow cavities than in those made in broad cavities. The mean length of a cell with a female exceeded that of a cell with a male. Females provisioned the nest cells with weakly paralyzed larvae of curculionid beetles. The cocoon looked as whitish cobweb-like film and could be detached from the cell walls. The prepupae retained a high level of mobility during winter hibernation. Adult feeding was recorded on flowers of 12 plant species belonging to 9 families. Only 3 of them had nectar accessible to A. mocsaryi while 9 species were specialized melittophilous (7 species) or psychophilous plants (2 species). The wasps obtained nectar from flowers of the latter plants through holes in the perianth which they gnawed out with their mandibles. The nest partitions were found to contain monosaccharides; this indicates that wasp females use nectar as building material, to moisten and bond dry soil and sand particles. Water collection by female A. mocsaryi was recorded only once. The species is univoltine. The sex ratio is female-biased. Attachment behavior of the females to the point of their emergence from mother nests (philopatry) was recorded. The nests were infested with the parasitoid wasps Melittobia acasta and Hoplocryptus coxator, a larva of the beetle Trichodes apiarius, and a puparium of an unidentified tachinid fly. The progeny mortality was 38.8%. Nesting of A. mocsaryi is discussed in relation to the phylogenetic position of the genus Alastor. The use of nectar as building material may be related to nectar robbing from the flowers of many plant species; this feature may also be characteristic of some other members of the subfamily Eumeninae.