An Ethological Study of the Digger Wasp Bembecinus Neglectus, With a Review of the Ethology of the Genus

Abstract

[The behavior of the small digger wasp Bembecinus neglectus (Cresson) is described for the first time. The observations were made from June 24 to July 13, 1953, in an area of sandy glacial drift in Pottawatomie County, Kansas. Males were observed June 24- July I walking in small circles on the sand, taking short, hopping flights, and pouncing upon other males and females in attempted matings. Activity in the colony usually started about 9 a.m. and was at its height until 2 p.m. Females were present and engaged in nesting activities throughout the period of observation. The nest is dug by the female in about one hour; the burrow length averaged 11 cm. and the depth of the cell averaged 7.8 cm. The majority of individuals prepared a second cell in the same nest after the first one was fully provisioned. The egg is laid in the empty cell glued at about a 45° angle to the top of the small lump of sand grains, slanted away from the entrance to the cell. The day after oviposition, before the egg hatches, from one to three leafhoppers are brought in and placed head-in, venter-up, beside the egg. After the egg hatches, the larva is fed progressively for two or three days, until the cell is full and is closed off. From 10 to 15 leafhoppers are provided per cell. Two species of leafhoppers were used in large numbers, and one specimen of another species was found (all adults) ; two nymphal Dictyopharidae were found in one nest. The wasp always closes the nest when leaving, and spends little time in the nest when not engaged in provisioning; a final closure is made when provisioning is complete. The known ethology of other species of Bembecinus is reviewed, all species appearing to agree rather closely with neglectus. The unique features in the behavior of Bembecinus are reviewed, and reasons are advanced for considering the resemblances of this genus with the bembicine wasps as due to parallelism in evolution., The behavior of the small digger wasp Bembecinus neglectus (Cresson) is described for the first time. The observations were made from June 24 to July 13, 1953, in an area of sandy glacial drift in Pottawatomie County, Kansas. Males were observed June 24- July I walking in small circles on the sand, taking short, hopping flights, and pouncing upon other males and females in attempted matings. Activity in the colony usually started about 9 a.m. and was at its height until 2 p.m. Females were present and engaged in nesting activities throughout the period of observation. The nest is dug by the female in about one hour; the burrow length averaged 11 cm. and the depth of the cell averaged 7.8 cm. The majority of individuals prepared a second cell in the same nest after the first one was fully provisioned. The egg is laid in the empty cell glued at about a 45° angle to the top of the small lump of sand grains, slanted away from the entrance to the cell. The day after oviposition, before the egg hatches, from one to three leafhoppers are brought in and placed head-in, venter-up, beside the egg. After the egg hatches, the larva is fed progressively for two or three days, until the cell is full and is closed off. From 10 to 15 leafhoppers are provided per cell. Two species of leafhoppers were used in large numbers, and one specimen of another species was found (all adults) ; two nymphal Dictyopharidae were found in one nest. The wasp always closes the nest when leaving, and spends little time in the nest when not engaged in provisioning; a final closure is made when provisioning is complete. The known ethology of other species of Bembecinus is reviewed, all species appearing to agree rather closely with neglectus. The unique features in the behavior of Bembecinus are reviewed, and reasons are advanced for considering the resemblances of this genus with the bembicine wasps as due to parallelism in evolution.]