Our Native Squash Bees

Squash Bee
Copyright 2007 Jim Cane
All Rights Reserved

Utah’s wintry weather seemed interminable this year, but at long last, full summer is upon us. Balmy days ripen the bounties of our orchards and gardens, including vast quantities of squashes: zucchini, crookneck, banana, butternut, and later, the pumpkins for Halloween. Squashes require pollinators. . Foraging bees inadvertently move the pollen from the male flowers to fertilize female flowers. Such pollination by a bee will result in the seeds you encounter when you slice open a squash. Without developing seeds, no squash will form, so pollination by bees is vital.

New research is showing that a specific group of unmanaged native bees is largely responsible for pollinating our squashes, gourds and pumpkins. From Maine to California, and all around Utah, these so-called squash bees are busily visiting flowers of all of our squashes, from acorn to zucchini. In fact, they are only visiting these flowers, as these bees are strict floral specialists. Beginning at dawn, male squash bees can be seen darting among squash flowers, seeking receptive mates and the odd sip of nectar to fuel their flight. Females load up on nectar and the bright orange pollen to cart back to their nests. Unlike honeybees, each female squash bee has her own nest, consisting of a simple underground burrow. She provisions each of her offspring with a cache of pure squash pollen and nectar. By 9AM, their frenetic morning of foraging complete, female squash bees head home to rest and work on their nests. Through their early morning foraging activities, they daily pollinate each day’s new flush of flowers.

Zucchini Squash with Flowers

If you grow squashes, you are likely to find their flowers being visited by squash bees. Look for these bees around breakfast time, between sunrise and 8:30. They fly more quickly and deliberately between flowers than the slightly larger, later-flying honeybees. Unlike honeybees, female squash bees carry their pollen dry in a brush of hairs on their hind legs. Later, you may discover sleeping male squash bees by pinching the wilted, closed flowers. A drowsy buzz reveals a defenseless male squash bee sleeping within. There he will snooze until dawn, which brings a new flush of flowers, and with it, another chance for every squash bee Romeo to find his buzzy Juliet. All this drama, and you thought you were just growing zucchini!

Credits:

Photos: Courtesy and © Copyright 2007 Jim Cane
Squash Bee Video © Copyright 2008 Lyle Bingham

Text: Bridgerland Audubon Society: Jim Cane

Additional Reading:

Squash Pollinators of the Americas Survey (SPAS), James Cane, USDA Pollinating Insect Research Unit, Utah State University
http://www.ars.usda.gov/Research/docs.htm?docid=12041

Celebrating Wildflowers, Pollinator of the Month, Squash Bees, Jim Cane, USDA ARS, Bee Biology & Systematics Lab, Logan, Utah
http://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/squash_bees.shtml

Videos:

Squash Bee Peponapis & Sunflower Bee Melissodes agilis in Ontario 2, http://www.youtube.com/watch?v=rXMmLjTYp3k
Squash Bee Peponapis & Sunflower Bee Melissodes agilis in Ontario 1, http://www.youtube.com/watch?v=r0Hvfz1o3Iw

Bee Pollinators of Southwest Virginia Crops (revised 6 June 2010), http://www.youtube.com/watch?v=l_etyEdu9fQ

Crop domestication facilitated rapid geographical expansion of a specialist pollinator, the squash bee Peponapis pruinosa, Margarita M. López-Uribe, James H. Cane, Robert L. Minckley, Bryan N. Danforth
Proc. R. Soc. B 2016 283 20160443; DOI: 10.1098/rspb.2016.0443. Published 22 June 2016http://rspb.royalsocietypublishing.org/content/283/1833/20160443.abstract