Cliff Shierk lays out a grid of traps:
We were pretty sure we knew a thing or two about bees but Cliff explained that of the 20,000 species of bees, 85% are solitary and don't build hives. All of a sudden, we were disenchanted with bumblebees and were hoping to catch one of the 5,000 other varieties that are found in the US. Perhaps a Digger Bee, or a Sweat Bee, or a Cuckoo Bee!
Cliff laid out a series of traps, that are simply cups painted to mimic flower colors and filled with soapy water. The soap releases the surface tension of the water so insects stopping by for a drink can't land on the surface and instead fall in. Cliff came back first thing on Saturday morning to pick up the traps.
We're still awaiting the data but in the meantime you can find out more about the project here: http://chicagobees.blogspot.com/