Nuts in May

'In fact, if I hadn't been told that you would be here, I shouldn't have come to this party. Can't stand these gatherings of Nuts in May as a general rule. They bore me stiff.'

A Man of Means. 3 The Theatrical Venture

I don't know if you have ever tried to gather frogs. It is one of the most difficult forms of gathering there is. Rosebuds – easy. Nuts in May – simple. But to collect and assemble a platoon of lively young frogs against time is a task that calls for all that a man has of skill and address.

Laughing Gas, Chapter 17

 This reference comes from the Annotations compiled in Madame Eulalie's site