Temporal transition of nesting activities in the digger wasp Bembecinus tridens (Hymenoptera, Crabronidae).

A nest aggregation of Bembecinus tridens (Hymenoptera: Crabronidae) was investigated through observations of marked individual females in Northern Italy, in order to quantify frequencies, duration, and sequence of the nesting activities. Wasp females dug unicellular (in one case multicellular) nests preferably on oblique surfaces. Nest digging occurred mainly in the morning, while definitive nest closing was performed only in the afternoon, and nests were frequented by the owners for 3.52 days on average. One to eight nests were dug by single females in rapid succession in the area observed, revealing a rapid dispersion towards other sites. Provisioning and non-provisioning (control) flights were positively correlated and occurred mainly in the late morning. A number of orientation flights followed most exits from the nests but was higher at the end of nest digging. Nest closing lasted more at the end of provisioning and at the end of digging. Provisioning began more frequently one day after nest digging (and oviposition), less frequently two days after, and the number of prey per day was negatively correlated with the number of provisioning days. Data are consistent with a situation of primitive progressive provisioning, and match that of other species of the same genus.