Squash Bees

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Three Squash Bees
Peponapis pruinosa
Copyright © 2009 Jim Cane

At long last we are enjoying full summer, and with it, the bounty of our gardens. Last August on this program, you learned about our native squash bees. Unlike honeybees and bumblebees, Squash bees are not social. Each female excavates a simple vertical tunnel in the dirt the diameter of a pencil. Lateral tunnels terminate in tiny chambers where she caches pollen and nectar to feed her progeny. She lays one egg per chamber. These nests are well concealed.

But you can readily see the feverish activity of males and females at squash, pumpkin and gourd flowers soon after sunrise, often before honeybee activity. Squash bees are the size of honey bees, but earlier, faster and more deliberate in their flight. Males have a yellow spot on the face. Unlike honeybees, female squash bees carry squash pollen dry in a brush of hairs on their hind legs.

Both sexes of squash bee are valuable pollinators, indeed they are the unheralded pollinators of most of the nations squash and pumpkins. But there is more to their story in Utah. Their native hosts, the wild gourds, only grow in the hot low deserts. Native Americans domesticated and cultivated squashes and gourds, but the practice did not spread north of the red rock country. Across most of Utah and the northern US in general, we have squash bees because we grow squash. In Utah, European settlers first grew squashes only 150 years ago. Each annual generation of squash bees spread further north, hopscotching from homestead to homestead, reaching as far north today as Boise Idaho. As you pick your zucchinis, butternuts and pumpkins, realize that your squash’s flowers also fed the descendants of our squash bee pioneers.

This is Linda Kervin for Bridgerland Audubon Society.

Credits:

Photo: Courtesy and © Copyright 2009 Jim Cane

Text: Jim Cane, Bridgerland Audubon Society

Additional Reading:

Our Native Squash Bees, Wild About Utah, 12 August 2008, http://www.wildaboututah.org/080812squashbees.htm

Squash Pollinators of the Americas Survey (SPAS), James Cane, USDA Pollinating Insect Research Unit, Utah State University

2009: http://www.ars.usda.gov/Research/docs.htm?docid=16595

2005: http://www.ars.usda.gov/Research/docs.htm?docid=12041

Perfect Pumpkin Pollinators: The Squash Bees!, James Cane, Frank A. Eischen, Blair J. Sampson, USDA-ARS, http://www.ars.usda.gov/is/AR/archive/nov08/bees1108.htm Also published in Agricultural Research magazine Nov/Dec 2008 http://www.ars.usda.gov/is/AR/archive/nov08/

Across the Americas, Squash and Gourd Bees Are Superb Pollinators, Marcia Wood, Dec 30, 2008, http://www.ars.usda.gov/is/pr/2008/081230.htm

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

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

Bumblebee Queens of Spring

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Bombus bifarius,
Copyright © 2008 Don Rolfs

This is Linda Kervin for Bridgerland Audubon Society.

When crocuses are pushing through the snow in your garden, you might see another sign of spring: the flights of bees. Other bees may fly in spring, but few are as early or as boisterous as bumble bees. Utah is home to more than a dozen species of bumble bees, all of who belong to the genus Bombus (which in Greek means buzzing). All have a combination of black and yellow markings on their bodies. Some also have orange bands. Unlike honey bees that pass the winter warmly clustered in hives, bumble bees overwinter as solitary queens, dormant under a few inches of loose soil or leaf litter. These queens are quiescent all winter until warming soil beckons their reawakening to start their colony.

From March to May, watch for a behavior called nest searching, when the big, burly queen bumble bees fly low over the ground, stopping often to investigate holes in the earth or in building foundations. Bumble bees nest in small, insulated cavities, such as abandoned rodent burrows or bird houses. Once the queen finds a suitable nest site, she is out and about, foraging for pollen and nectar to provision her offspring. After a few days she will have sufficient food to begin laying eggs. Like all bees, her offspring progress through four life stages: egg, larva, pupa and adult. In just under a month, her daughters develop into adults, each chewing free of its cocoon.

Bombus griseocollis Queen
Foraging on Hedysarum
Copyright © 2008 Jamie Strange

These daughters take over foraging and nest construction duties, leaving the queen to remain in her nest and continue to lay eggs and incubate her brood. Workers are often much smaller than their mother, so don’t expect to see many big bumble bees again until autumn, when next year’s queens start the cycle anew, searching for mates and a spot to spend the winter.

This is Linda Kervin for Bridgerland Audubon Society.

Credits:

Photo: Courtesy & Copyright © 2008 Don Rolfs & Jamie Strange

Text: Jamie Strange, USU USDA-ARS Pollinating Insect Research Unit

Additional Reading:

ID a Bumblebee, http://www.ars.usda.gov/Services/docs.htm?docid=10749

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