Pollinator Week BINGO!

Every year, a week in June is dedicated to celebrating pollinators. All week long TPI will be posting pollinator-related videos, blog posts, etc. PLUS, you can play BINGO for a chance to win a prize!

To play Pollinator Week BINGO, which features flower-visiting insects you can find in the Northeastern USA this time of year, download and print the Bingo card (below) or screen shot the image on your phone. Take your card/phone outside and if you find the correct insect, mark it off on your printed card with a pen/pencil or with your phone’s photo annotation option.

If you get BINGO! (five in a row, vertical, horizontal, or diagonal, TPI logo is a free space), send a photo of your annotated card to tuftspollinators@gmail.com or tweet a photo and tag @PollinateTufts by 11:59 pm on Friday, June 26. Each completed BINGO! card will be entered in a drawing to win TPI swag and a voucher for a free pollinator-friendly plant at next spring’s TPI plant sale! Limit one entry per person.

For help identifying the insects you observe, download our identification guides or reach out to us with photos via email or Twitter!

Stay tuned for more #PollinatorWeek fun!

Happy World Bee Day!

Did you know there are 20,000 species of bees in the world? And that 4,000 of those species are native to North America? In celebration of World Bee Day, we highlight some of the bees TPI members have studied across the United States and in Costa Rica.

Common eastern bumble bees (Bombus impatiens) are important pollinators of greenhouse tomatoes, blueberries, and pumpkins.
Photo: Genevieve Pugesek

Though the common eastern bumble bee is one of the more common bee species in the Northeastern US (as its name suggests), we still have a lot to learn! With help from Tufts undergrad and grad students, I am working to understand where queen eastern bumble beeshibernate. As it turns out, unlike most other species of bumble bees, these queen bees hibernate right next to the nest they were born in. So, if you are creating habitat for nesting bumble bees, you might be creating habitat for hibernating queens too! If you visit our pollinator gardens (while practicing safe social distancing) this spring, you’re likely to see these fuzzy bumble bees flying around.

Genevieve Pugesek, PhD Student, Tufts University

Yellow-faced bumble bees (Bombus vosnesenskii) pollinate many wild plants as well as crop plants such as tomatoes and berries.
Photos: Elizabeth Crone, Rachael Bonoan

For the past 5 years, I worked on this species in collaboration with Neal Williams (Assoc. Professor, University of California), Rosemary Malfi (now post-doc, UMass Amherst) and Natalie Kerr (now post-doc, Duke University).  We found that yellow-faced bumble bee colonies especially need resources to forage on during early stages of colony development.  In the same way that early childhood nutrition affects human health throughout their lives, early spring flowers help these bumble bee colonies grow!  Spring resources allow colonies to produce larger worker bees that are better at foraging for resources, leading to higher resource return even after the spring pulse of flowers ends.  The importance of spring resources has implications for bee conservation because native plants in California mostly flower during the wet spring, whereas irrigated crop plants mostly flower in the dry summer.  If we want yellow-faced bumble bees to be around to pollinate summer crops, we need to keep spring flowers on the landscape.

Elizabeth Crone, Professor, Tufts University

Hibiscus bees (Ptilothrix bombiformis) pollinate plants in the Malvaceae family including cotton, hibiscus, and saltmarsh mallow.
Photo: Judy Gallagher, Flickr

I spent a summer surveying native bees along Virginia’s Eastern Shore and studying the effects of sea level rise on native bee communities. The hibiscus bee was the most common species found on farms, meadows, and salt marshes along the coast. On steamy summer mornings, this bumble bee doppelganger could be found buzzing around marsh hibiscus or visiting blooming cotton fields.

Jessie Thuma, PhD Student, Tufts University

Blueberry cellophane bees (Colletes validus) are specialists that pollinate blueberries.
Photo: Max McCarthy

Different bee species have different diets; some collect pollen from a wide variety of flowers (generalists) while other species forage on the flowers of only a few types of plants (specialists). I sampled pollen from blueberry cellophane bees to understand what types of floral resources this species uses throughout its flight season in May and June. After identifying pollen samples under a microscope, I found that, true to their name, these bees rarely collect pollen from plants other than blueberry bushes.

Max McCarthy, Undergraduate, Tufts University

Honey bees (Apis mellifera) are generalist forages known to pollinate our crops.
Photo: Rachael Bonoan

I study how honey bees regulate in-hive temperatures in order to protect temperature-sensitive eggs and larvae. In order to develop properly, honey bee larvae must be kept at 32 – 36 °C (about 89 – 96°F). With the help of NSF REU students, I found that when an area of a honey bee hive is exposed to heat stress, the queen stops laying eggs in the “too hot” area. Instead of raising young in this hot spot, worker bees store nectar (food!).

Isaac Weinberg, PhD Student, Tufts University

Squash bees (Peponapis pruinosa) are known for pollinating…you guessed it…squash.
Photo: USDA ARS, Wikimedia Commons

As a lead field technician at UW-Madison, I worked with a team to investigate how the diversity and abundance of floral vegetation on small-scale organic farms impacted bee communities and crop flower visitation. We were interested in cucurbit (e.g. cucumbers, watermelons, squashes) pollination, as these crops rely solely on insect pollination. While I was fortunate to study a diversity of bees in this project, my heart was captured by Peponapis as the males scurried around giant squash flowers. Fun fact: When the squash flowers close mid-day, squash bee males nestle up and sleep in the protection of the closed flower until they reopen the following day. 

Sylvie Finn, Incoming PhD Student, Tufts University

Yarrow’s fork-tongue bee (Caupolicana yarrowi) pollinates wild nightshade, and is parasitized by a cuckoo beeTriepeolus grandis.
Photo: Nick Dorian

Yarrow’s fork-tongue is a large, ground-nesting solitary bee that inhabits high deserts of southwestern US and Mexico. Unlike most bees, it cannot be found during the day, but instead is active pre-dawn and post-dusk. In August 2018, several participants of the 2018 Bee Course and I woke up extra early to find nesting females. We found three nests and carefully excavated the long, sinuous tunnels to claim our prize: brood cells. Most cells contained just a Yarrow’s fork-tongue larva feeding on a slurry of pollen and nectar. In one cell, however, we also found an intruder: the larva of a cuckoo bee (Triepeolus grandis). With formidable mandibles, the cuckoo bee larva kills the host and develops on the stolen provisions. This may sound malicious, but it’s simply how the cuckoo bee lives. About 15% of all bees are cuckoos, meaning these pollinators would cease to exist without their host bees!

Nick Dorian, PhD Student, Tufts University

Stingless bees (Trigona spp.) are generalist tropical pollinators that forage on flowers and meat.
Photo: Rachael Bonoan

This past January, some TPI members traveled to Costa Rica with Tufts University’s Tropical Ecology and Conservation course. There, Nick and I studied mineral preferences of facultative “vulture bees,” stingless bees that forage at meat as well as flowers. We identified five species of bees (including Trigona silvestriana, pictured above) foraging at our baits and found that compared with unaltered baits (i.e. raw chicken), stingless bees tended to avoid baits soaked in calcium and potassium. In contrast, bees visited sodium-soaked baits just as often as unaltered baits. This suggests that like many herbivores, meat-foraging bees are likely limited by sodium and will suck up the salt wherever they can find it!

Rachael Bonoan, post-doctoral researcher, Tufts University

Orchid bees (Euglossa spp.) are known for pollinating orchids in the tropics.
Photo: Atticus Murphy

Can you see the thin yellow object on the back of this shiny green orchid bee? This is a pollinium, a packet of pollen grains, likely from an orchid. Male orchid bees forage at flowers for nectar, which provides nutritional energy, and floral scents, which are used to court females. In Costa Rica, my research partner and I captured orchid bees and used tiny glass tubes to suck up the contents of the crop, where collected nectar is stored. We measured sugar content of the bee-collected nectar and found that bees caught in human-dominated open spaces had more dilute crop contents than those caught in the forest. This may be because the open spaces were sunnier and hotter, driving the bees to drink more water.

Atticus Murphy, PhD Student, Tufts University

Interested in learning more about the bees in your backyard? Check out our insect identification guides! For even more bees, our favorite books are The Bees in your Backyard by Joseph S. Wilson and Olivia Messinger Carrill and Bees: An Identification and Native Plant Forage Guide by Heather Holm.
TPI members at work!

Thank squash bees for your pumpkins

Nothing says fall quite like pumpkins. They feature prominently in seasonal pies and Halloween decorations. Contests are held and won at county fairs by the farmers that can grow the largest pumpkins (some weighing in at more than 2000 lbs). Their appearance on the shelves of stores and farm stands marks the start of a season of aster and goldenrod, of cold nights and falling leaves, of root vegetables and mulled ciders. Amidst all this pumpkin hubbub, it is easy to take for granted our favorite orange squashes and lose sight of where they come from.

All pumpkins are a single species of squash, Cucurbita pepo, which is a scraggly vine native to the desert southwest. Over thousands of years, C. pepo was transported across North America and diversified through careful cultivation by native peoples and modern agriculture into many of the squash cultivars we love today: acorn, spaghetti, delicatta, and pumpkins. But it wouldn’t have been possible without some (tiny) help along the away.

Earlier in summer, this patch of ripe pumpkins was a field full of flowers and wild bees. Pumpkins are dependent on bees for pollination, and a single species of squash bee (Eucera pruinosa) perform the lion’s share of the work in New England. PC: Public domain

Every pumpkin starts out in mid-summer as a female squash flower, a yellow starburst peeking through huge green paddle leaves. Squash plants are monoecious (mon-ee-shus), meaning that male and female parts occur in separate flowers on the same plant. So, one squash plant contains flowers that produce pollen (male) and others that produce ovaries (female). In order for a female flower to be fertilized and successfully produce a fruit (yes, all squash are fruit), pollen from the male flowers must be transferred to the female flowers. This is pollination.

In natural and agricultural systems, wild bees are the main transporters of squash pollen. Early in the morning, squash flowers open up and produce prodigious quantities of sugary nectar to attract pollinators. Once in the male flower, the bee is passively dusted by squash pollen which it transfers to the next female flower that it visits. And so on and so forth until afternoon when the squash flower closes, never again to reopen. Hopefully, during its single day of blooming, it received a visit from a bee!

Squash bees (Eucera pruinosa) are important pollinators of pumpkins. Here you can see one lapping up nectar at the base of the flower. PC: Flickr

Which bees, however? Squash bees (!), so called because they feed their offspring exclusively with squash pollen (plants in the genus Cucurbita). There are around 20 species of bees that specialize on squash, but in New England we have just one: Eucera pruinosa (formerly Peponapis pruinosa). But, this bee is not historically native to New England. Recent genetic analyses show that squash domestication and trade over thousands of years enabled the squash bee to colonize New England from the desert southwest via the Great Plains. Thus, the squash bee exists in New England solely because humans are unwavering in their love for squash. You can think about this in another way: if all of New England were to stop growing squash for a single year, squash bees would be swiftly extirpated from the area.

Since squash bees are pretty picky about the pollen they consume, their seasonal activity period is limited to peak squash flowering season in Massachusetts, generally from mid-July to early August. Males emerge first and quickly establish territories at the best place to find a female squash bee: squash flowers! Although male solitary bees are often considered only useful as mates, because of this behavior, male squash bees are uncharacteristically good pollinators; they contribute heavily to the $200 million annual industry of pumpkin production.  

Once mated, female squash bees build their nests at the edges of squash fields in bare, packed soil. Because they are solitary, every female builds and provisions her own nest, though often nests will occur in close proximity to one another. She excavates a narrow tunnel through the soil, and every day prepares a chamber, fills it with a stiff oval of squash pollen and nectar (think play-doh consistency), and lays a crescent-shaped egg. This chamber contains everything the young squash bee needs to develop from egg to larva to adult. Squash bees will spend the winter underground and won’t emerge until the following summer when squash is flowering again.

Squash bees are solitary, meaning each female build a single nest underground. And the end of each side tunnel, she provisions a single offspring with pollen and nectar from squash flowers. Adult squash bees are active only for four-six weeks in late-summer. PC: Chan et al. (2019) Sci. Rep. 9: 11870.

How good are squash bees at making pumpkins? So good that many farmers refused to believe it. Historically, squash pollination was supplemented with commercial hives of honey bees and, in some cases, bumble bees. Yet, it has been shown that farm fields supplemented with managed bees do not produce bigger yields than ones receiving only wild pollination. There are two explanations for this. First, most other bees refuse to collect squash pollen for their offspring, possibly because of distasteful chemicals. Thus, managed bees are only visiting squash flowers for nectar and come into less contact with pollen. Second, squash bees are such efficient foragers and their daily schedule so synchronized with the daily schedules of squash flowers, that by the time other bees arrive, the flowers have already received sufficient visits to produce big pumpkins. Still, many farmers bring in managed bees to pollinate their pumpkins as an insurance policy.

This Halloween, if you carve a pumpkin or drink a spiced latte, thank squash bees. Our obsession with pumpkins enables these abundant pollinators to survive and grow in the most unlikely of places (even in the middle of Medford), and their unrelenting obsession with cucurbit pollen gives us more pumpkins than we know what to do with.

P.S. If you want to get a close up look at a squash bee, one afternoon, late next summer, find a closed squash flower in a garden. Chances are that a male squash bee is dozing inside, perhaps having found a mate that morning or just missed his opportunity. Look for goofy-long antennae, ochre hairs, and a boldly striped abdomen.