Patterns of nest provisioning and parental investment in the solitary digger wasp <i>Ammophila sabulosa</i>

It is suggested that the flexible provisioning strategy used by A.sabulosa allows a wide range of prey sizes to be utilized without affecting maternal control of offspring size and sex, which could be important when available prey sizes vary temporally and spatially.

Abstract

Abstract. In nest‐building wasps there is a continuum from species that provision each offspring cell with one large prey item (single provisioning) to species that provision each cell with many small items (multiple provisioning). The significance of number of prey per cell was examined during two seasons in Ammophila sabulosa (L.), a species that provisions between one and five caterpillars per cell. There was no difference between the total weight of prey in singly‐provisioned and multiply‐provisioned cells: individual caterpillars placed in multiply‐provisioned cells were smaller. Small caterpillars were captured and transported to the nest faster than large ones. If the first prey provisioned was large, the cell was usually then permanently closed. If the first prey was small, additional prey were captured, and females appeared to become more selective: additional prey were rarely large. It is suggested that the flexible provisioning strategy used by A.sabulosa allows a wide range of prey sizes to be utilized without affecting maternal control of offspring size and sex. This could be important when available prey sizes vary temporally and spatially. There was a male‐biased first generation investment ratio. Female‐producing cells were provisioned with a higher total prey weight than male‐producing cells, and conversion of prey weight to adult weight was more efficient for females. Total prey weight provisioned is probably a good indirect measure of parental time investment in A.sabulosa. Other measures, particularly number of prey provisioned, will be less accurate.