Nest abandonment in the solitary wasp Cerceris arenaria (Hymenoptera : Crabronidae): Escape, leave open or destroy the door?

Nest is an important resource for fossorial Hymenoptera, and it becomes very limiting in those species that rarely dig new burrows but commonly re-use existing (conspecific) ones. A population of the solitary digger wasp Cerceris arenaria (Hymenoptera: Crabronidae) was observed during two nesting seasons to assess frequency, distribution, and behaviors related to nest abandonment and to estimate possible advantages of different choices. Females permanently left their nests in one of the following three different ways: i) after a nest usurpation event, ii) voluntary departure leaving the entrance open and iii) voluntary departure after enlarging the entrance. The major cause of nest abandonment was due to nest usurpation, which occurred mainly in late afternoon. Females were advantaged during usurpation attempts if they are the nest owners and larger than the intruders. Voluntary abandonment was more frequent in the morning and at the end of the flight season. Since voluntarily abandoned nests had smaller nearest neighbor distances when compared with non abandoned nests and the frequency of total usurpation attempts was negatively correlated to the distance to the nearest nest, we propose that disturbance by conspecific females may be, at least in part, at the base of the voluntary nest abandonment in this wasp. This was supported by the fact that nest-searcher females accepted nearly every available nest, independently from the number of prey therein included, in contrast to a previous hypothesis. Those nests voluntarily abandoned after entrance enlarging were not visited by conspecific females or cuckoo wasps and flies.