I'm the "Bee Guy" for a large solar plant being built in the south western California Desert . Today they called me out to check out reports of their guys being stung by these grey bees ( originally thought to be covered in wet concrete ) They said the bees are attracted to their orange vests. I collected several dead specimens from in and around their office trailers ( see photos ) . A quick search found them to be Pallid Bees. A ground dwelling bee. I've been out here for 30 years and have no recollection of seeing this bee. Although I have had others tell me that they've seen them. Has anyone ever dealt with these bees ?