Nest architecture and brood mortality in four species of sweat bee (Hymenoptera; Halictidae) from Cape Breton Island

Abstract

PACKER, L., SAMPSON, B., LOCKERBIE, C., and JESSOME, V. 1989. Nest architecture and brood mortality in four species of sweat bee (Hymenoptera; Halictidae) from Cape Breton Island. Can. J. Zool. 67: 2864 -2870. The nest architecture of four species of the bee family Halictidae from Cape Breton Island, Nova Scotia, was studied. Augochlorella striata and Lusioglossum (Evylaeus) comugenense constructed their brood cells in a cluster surrounded by a cavity. In the case of A. striata, the cavity-forming habit increased the rate at which the soil of the brood cell cluster dried out, relative to the surrounding soil. The year of the study was unusually dry and in midsummer the moisture content of the soil was extremely low. This weather pattern seemed to result in some mortality of A. striata brood due to dehydration, and prevented foundresses from constructing brood cells. The two other species, Lusioglossum (Evylaeus) cinctipes and Lusioglossum (Dialictus) laevissimum, did not construct brood cell clusters. All four species had shallower nests than other species with similar nest architectures for which published data are available. All species except L. laevissimum nested in association with stones at the ground surface. It was shown that brood cells of nests situated close to rocks and stones were likely to experience increased temperature, presumably resulting in a faster developmental rate for immatures. This may be important in the Cape Breton environment, which is clearly marginal for social sweat bees. Both A. striata and L. comagenense exhibited very low mortality rates in developing immatures (1 and 7%, respectively). PACKER, L., SAMPSON, B., LOCKERBIE, C., et JESSOME, V. 1989. Nest architecture and brood mortality in four species of sweat bee (Hymenoptera; Halictidae) from Cape Breton Island. Can. J. Zool. 67 : 2864-2870. On trouvera ici des donntes sur l'architecture des nids de quatre espkces d9Halictidae de 1'Ple du Cap-Breton, Nouvelle~c o s s e . Chez Augochlorella striata et Lusioglossum (Evylaeus) comugenense, les cellules larvaires sont rassemblkes en groupes et entourkes d'une cavitC. Dans le cas d'A. striata, la formation de la cavitk entrafne la dkshydratation plus rapide de la terre qui forme les cellules que du sol environnant. L'annke de 1'Ctude s'est avkrke une annke particulikrement skche et, au milieu de l'ktk, le contenu hydrique du sol Ctait extremement bas. Ces conditions semblent avoir entrain6 une certaine mortalitk par dkshydratation au sein du nid des A. striata et elles ont empechk les fondatrices de construire de nouvelles cellules larvaires. Les abeilles des deux autres espkces, Lusioglossum (Evylaeus) cinctipes et Lusioglossum (Dialictus) laevissimum, n'ont pas construit de cellules regroupkes. Les quatre espkces avaient des nids peu profonds par comparaison aux donnkes de la littCrature sur d'autres espkces B nids d'architecture semblable. Chez toutes les espkces, sauf chez L. laevissimum, les nids ktaient associCs B des pierres B la surface du sol. 1' 1 a Ct C dCmontrk que les ce...

Allozyme variation, linkage disequilibrium and diploid male production in a primitively social bee Augochlorella striata (Hymenoptera; Halictidae)

“…This is because the low successional stage habitats required by these species are inherently unstable and even when large aggregations build up they may be extirpated as a result of increases in predator and parasite populations (Knerer, 1973). The population under consideration was estimated to consist of around 1000 nests and is unlikely to have persisted for more than twenty years (Packer et a!., 1989b). Large effective population size is unlikely to be a cause of the high level of genetic variation in this marginal, isolated population.…”

“…The study site was at Irish Cove, Richmond County, Cape Breton Island, Nova Scotia (see Packer et al, 1989b, for a detailed description of the study site and nesting biology of the population). Bees used for electrophoresis were captured at the nest site late in summer 1987, after foraging activity had ceased; at various times during the spring and summer of 1988; or from nest excavations during 1987.…”

Spatio‐temporal variation of colony structure and eusociality level of the Japanese sweat bee Lasioglossum (Evylaeus) duplex (Hymenoptera: Halictidae)

“…Nest depth and cell depth are spatio-temporally variable in Lasioglossum duplex as has already been reported in some sweat bee species (Packer et al 1989). In Augochlorella striata, for instance, mean depth of deepest cells within a nest ranges from 5-20 cm, with deeper nests in drier locations and during different seasons of a year (Ordway 1966).…”

Landscaping pebbles attract nesting by the native ground-nesting bee Halictus rubicundus (Hymenoptera: Halictidae)

“…Female H. ligatus preferentially placed their entrances against basal plant rosettes (Packer and Knerer 1986), a useful trait in gardens. On Cape Breton Island, Canada, the halictid bees Augochlorella striata , Evylaeus cinctipes , and E. comagenense all situated their nest entrances next to surface stones, which were found to warm the adjacent soil (Packer et al 1989). A fourth species, Dialictus laevissimum , nested without regard to surface stones.…”

“…This aggregation has persisted for 13 years but is lately dwindling as weedy annuals have been allowed to proliferate, shading the surface. Related halictid bees placed their nests next to or even under surface stones (Packer et al 1989). Many opportunities exist to evaluate practical modifications of soil surfaces to make our pollinator gardens more welcoming to native bees.…”