Stalking the Native Squash Bee

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The summer season is in full swing at our gardens. With it come a number of challenges for raising healthy, productive crops. One of these is pollination. 

Plants in the "Cucurbit" family are particularly reliant on inset pollinators. This family includes common vegetable crops such as summer squash, cucumbers, melons, winter squash, pumpkins and gourds. Cucurbits have unisexual flowers and must have pollen moved from male flowers to female flowers to set a viable fruit. Female flowers that have not been pollinated will still produce a fruit, though it is often significantly smaller, shriveled, misshapen and doesn’t have seeds. Not an attractive sight on our farmers’ market table!

There are several insects that serve as pollinators in a squash patch, and it is beautiful to observe their activity when crops are in full bloom. Honeybees can play an important role is pollination, but they aren’t the only ones on the scene. 

Squash and other Cucurbits are native to the Americas and their domestication by indigenous farmers predates maize. The squash bee (Peponapis pruinosa) is also a native to North America, unlike the honeybee. Squash bees do not live in large hives with thousands of bees organized into social castes. The squash bee is solitary. They live in nests in the soil and produce just one generation each year. 

For the casual observer, they are difficult to tell apart from honeybees. There are several differences when you take a closer look. The squash bee has much more distinct light colored stripes on its abdomen. It also has combs, rather than a “pollen basket,” on its hind legs for carrying pollen. Click here to see some images of this striking bee.

This species has developed a very special relationship with squash, feeding primarily on the pollen of the Cucurbit family. They are considered extremely effective pollinators. As specialists, they make more contact with reproductive structures in the flower. They get to work earlier in the morning and move rapidly from flower to flower without deviating to other types of plants. This is important as each female squash blossom only opens for a single day. One flowers requires about 15 visits from bees to become pollinated successfully. 

We have caught them mating in squash flowers. Males will overnight in the closed blooms-- rather than returning to their soil tunnels-- ready to get back to work in the morning. At first light many days this season, we have had the pleasure of seeing squash bees emerging from their underground nests, just below the leaves of our cantaloupe vines. 

To encourage squash bees in your garden, it is best to avoid deep tillage and excessive disturbance of the soil between crops. It is also helpful to maintain untilled, hedgerows or marginal areas in close proximity to the garden which can provide additional nesting area.

We have learned an incredible amount about this and other species of native bees from the Xerces Society. This organization does an excellent job working with farmers and publishing resources to help gardeners learn how to improve practices to support native pollinators. We can all make a small difference to encourage the diversity of insect pollinators that are critical to our food supply.