Start: 7:30 a.m. April 3
End: 6:00 p.m. April 3
Habitat: Patuxent River, bottomland, young deciduous woods, many spring beauties in bloom
Bees: Andrena, Osmia, Lasioglossum
Experiment: 24 bowls of 3.25 ounce white solo brand bowls laid in a transect through the woods and placed 5 m apart. Every other bowl was filled with a solution of soapy tap water (large squirt of blue dawn dishwashing liquid in a gallon of water). In the other bowls was placed a solution of soapy propylene glycol (large squirt of blue dawn dishwashing liquid in a gallon glycol). The glycol is RV glycol purchased from Walmart into which about 2 tablespoons of household bleach was added to remove the red dye, the concentration of the glycol was unknown but Walmart claims it will not freeze until you reach -51F (also untested).
Results below are detergent in the left column and glycol in the right column. They are presented as pairs, but in reality they are simply adjacent to one another in the transect. Numbers are total number of bees.
A straight t-test (numbers were normally distributed)
t: -0.6626 p(same): 0.51447
Did not indicate that the two treatments came from different sampling distributions and are thus not statistically different at the sample sizes presented.
95% conf. for difference between means: (-3.5499 6.8832)
So, the conclusion at least for this time, place, and community of bees is that soapy water and soapy glycol are equally effective.