RE: Defending the Professional Honor of Male Bees
Folks- I can add some to the discussion, although Vince covered the factors admirably. From my own data and an unpublished literature survey, males are inferior to females in their pollination efficacies at individual flowers, but they do deliver are some substantial fraction of it. Thus, for instance, male Megachile rotundata and Nomia melanderi are about 2/3 as likely to trip an alfalfa flower as a conspecific female ( I can send the reprint pdf). Contrast that with a honey bee, which is about 4%, as I recollect. Having stated that, of course, exceptions will be found. I am working out the energetics of flight for male Nomia to estimate their daily nectar needs, and so visits to alfalfa flowers for nectar. It appears that they contribute no more than 10% to the full yield of cultivated alfalfa (but then that is close to the grower’s profit margin), mostly because they only need nectar to fuel their flight, as Vince points out, so they don’t visit that many flowers in a day. Blair Sampson and I have a paper in revision that shows that male Peponapis can contribute substantially to fruit production at Cucurbita, but then, that is where they hunt for females as well as forage. The whole topic warrants more study. And then there are no doubt indirect effects, like male bee attentions driving females to other individual plants (or on alfalfa, it seems, to entirely different more distant fields!). It is nothing to proud of, but it is a straw to grasp at least!
James H. Cane
USDA-ARS Bee Biology and Systematics Lab
Utah State University, Logan, UT 84322 USA
tel: 435-797-3879 FAX: 435-797-0461
Gardening for Native Bees: http://extension.usu.edu/files/publications/factsheet/plants-pollinators09.pdf
"The obscure takes time to see,
but the obvious takes longer"
Edward R. Murrow