| Abstract: | - 1 Three species of pemphredonine wasps, Passaloecus insignis, P.gracilis and P.corniger, were observed nesting in disused beetle holes in pine boards. The species differed from one another in the size, height above ground and aspect of the holes selected as nest sites.
- 2 P.insignis and P.gracilis stocked their nests with aphids of several species, but P.corniger females stole paralysed aphids from nests stocked by P.insignis, P.gracilis or by conspecifics, sometimes breaking open the outer door of a nest to do so.
- 3 The outer doors of the nests were of pine resin; P.corniger and P.insignis added pellets of other material to the surface. P.corniger females revisited their nests after sealing the outer door and behaved as if scent-marking them, perhaps conferring protection against robbery by conspecifics.
- 4 Adult male wasps probably fed on honeydew. They appeared early and seemed to have a flying season of only a few days, whereas females probably lived and flew for about eight weeks after emergence.
- 5 The behaviour of nest-stocking female wasps is considered in relation to the temperature of their microhabitats.
- 6 The possible use of pemphredonine wasps for the biological control of aphids or thrips in glasshouses is discussed.
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