The jewel wasp (ruby-tailed wasp, Chrysis ignita?) looking for cells in which to lay its egg. Above this wasp were living red mason bee larvae, eggs and pollen in cells. Perhaps, like a burglar it knew where the goods were and thought it would try the back door whilst the occupants were out! A sneak theft, leading in most cases actually to a sneak death! Though in this case she left empty handed! This nest box had previously been used last year successfully by red mason bees.
The second wasp, Monodontomerus, is looking for red mason bee cocoons to parasitise. A cold calculated killer, kills her host whilst it is inside its cocoon when the adults are already dead in most cases, so there is little chance of confrontation. Again, there were red mason bee larvae and eggs in the nest itself at that time, but no cocoons. Again, last year this nest box was used successfully by red mason bees. Perhaps she was just seeing at what stage the red mason bees were at in their life cycle after seeking out potential nest sites or could she detect the chemicals from last years cocoons, even after washing the cavities out ?
Lastly and fleetingly, possibly a Symmorphorus bifasciatus wasp returning to where it was born in search for a nest site of its own? I just observed it flying around the nest box and suddenly it flew in but only for a very short time. The actual cavity she was in had not been used in the past but was about the same height as the one she emerged from and then I took down to replace it with my own nest box. All filmed early July 2013, different nest boxes, different days, different locations.
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