Thanks, everyone, for your great suggestions on vane trap protocols. There were a variety of answers from 6 people:
-4 people mentioned hanging traps: 1 vote for metal poles, 1 for wood stakes with hose clamps, 1 for 1.5m PVC pipe, and 1 did not specify.
-6 people reported their killing agents: 3 for water & Dawn, 1 for propylenge glycol & Dawn, 1 for vapona strips, and 1 for no agent at all.
-2 people reported their timing: 1 person checked traps after 24 hours, and 1 person after at least 5 hours.
There were a couple inquiries about where and what I'm collecting. The traps are placed in adjacent remnant and restored prairies on 4 Scientific and Natural Areas
in Minnesota. They're placed for 24 hours biweekly, near transects of 3.25-oz pan traps filled with water & Dawn (colored yellow, blue, or white from New Horizons).
The goal is to start a species list of bees for each site. We're also doing preliminary comparisons of bee diversity and abundance in remnant versus restored habitat. With the strange weather this year, though, it seems like bee numbers are down quite a bit.
Thanks again for all your help!