Hello Philippe; I have collected ground-nesting bees in Southern California and Arizona. An active colony has many individuals coming and going and we simply netted them over the nest hole. Or, in an active colony like that using emergence traps wouldn't require a wait time of more than a few minutes if you need certainty about which nest an individual came out of.

Of course the most direct method is to simply dig them out. That's disruptive to the colony and so should be avoided wherever possible.

Best regards, Jim Des Lauriers

Dear James

Thank you very much for your answer. For a colony I will definitely follow your approach. However, I was more thinking about species that don't nest in colonies with nests distributed over a larger area. In that case, it would be too time-consuming to wait at the nest for the bee to come out and only possible during favorable weather conditions. So I was hoping for a method that allows to just extract the female from the nest, without causing too much damage, like digging out. That would be faster and less dependent on favorable weather conditions compared to using emergence traps. But maybe emergence traps will be the best way to go, if one doesn't want to destroy the nest.

Best regards, Philippe

Philippe; Given all that, I would try the emergence trap method first. They look like they would be easy to make yourself. Cheers, Jim Des Lauriers