Wasp Spring

Sitting on the front porch this weekend I noticed many paper wasps scouting the rafters for a nesting site.  Between pages of the book I was reading I counted a maximum of five of them at one time.  Over the course of two warm days this weekend, one of them (and her assistant) had a few cells built directly over my head; on closer examination I could see eggs inside.  I also noticed some papery debris on the roof above the tiny nest.

When I mentioned to Mr. Cardui the wasps are nesting, he said he saw a nest the other day.  Sometimes that means yesterday, so I'm thinking he saw a larger nest in the same spot on Friday.  A bird must have taken the original nest; I remember hearing a mockingbird nearby that day.

Paper wasps are actively searching for nesting spots all around the house.  They favor sheltered overhangs, and our roof eaves and porches and patio covers seem to fit a wasp's image of home.  I found one scouting the inside of a cupboard on the porch.

I also saw a few wasps hunting and gathering wood fibers.  This one is scraping the top of an old decorative birdhouse for nest material.  This wasp and the one in the cupboard are Polistes exclamans; the ones on the front porch are P. apachus.  

Paper wasp females emerge in spring after having laid low in their hibernaculum over winter, having mated in autumn.  The questions I have are:  Where are these hibernaculi?  For what period of time do paper wasps really shelter in them in our mild southern California winters?  What is the stimulous to begin nest-building?