Blog – Page 12

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.

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.

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.

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.

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.

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.

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 bee, Triepeolus grandis.

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.

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.

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!

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Stop calling it the “murder hornet”

Recently, news outlets have been spreading fear of the “murder hornet” invading the United States. To be clear, the “murder hornet”, actually known as the Asian giant hornet (Vespa mandarinia), does not pose a direct threat to humans. While a sting from this hornet may hurt, Asian giant hornets are generally not aggressive unless provoked. Stinging is a form of protection, and like any stinging insect, the Asian giant hornet is not out to sting you.

Instead, Asian giant hornets are after much smaller prey: honey bees. Asian giant hornets are carnivores, meaning they feed insects to their developing young. A honey bee colony, with tens of thousands of bees, is a great place to collect protein-rich food. In one foraging trip, one Asian giant hornet can kill up to 40 honey bees! As you might imagine, a whole colony of these hornets could be fatal to a honey bee colony.

In their native range of eastern and southeastern Asia, Asian giant hornets have been predating on Asian honey bees (Apis cerana) for a long time. In response, Asian honey bees have adapted a defense strategy: heat. When the hornet invader is detected, worker bees sound the alarm by shaking their abdomens. Then, in a swift, coordinated response, hundreds of honey bees swarm the hornet and contract their flight muscles, generating intense heat. Together, the worker bees heat the hornet to about 117 °F, killing the intruder. As it happens, the hornet can only withstand temperatures up to 115 °F, while Asian honey bee workers can withstand temperatures up to 118 °F. Evolution is a beautiful thing.

Sterile female worker bees perform all the tasks in the colony, including taking care of the queen (white paint mark) and defending the hive from intruders.

But, the Western honey bees (Apis mellifera) that are managed in North America have not evolved with this predator and are not as well equipped to defend themselves. This is why we need to be worried about the Asian giant hornet. Managed honey bees provide valuable economic and ecosystem services such as beekeeper livelihoods and agricultural pollination—the Asian giant hornet jeopardizes the security of these services.

While this is certainly cause for concern, panic is unwarranted. Since August 2019, the Asian giant hornet has been spotted just three times in Washington State and three times in British Columbia. Following a recent report of a honey bee colony death that resembled the work of this hornet in Washington (although it is unconfirmed), Washington State Department of Agriculture entomologists are on the hunt to stop the hornet before it spreads.

Fortunately, Asian giant hornets have not been spotted on the east coast, and it would likely take a while for them to get here. As with any introduced species, however, attempts should be made to spot the hornets early on. If you think you have seen an Asian giant hornet in Massachusetts (which is currently highly unlikely) you can report a sighting to the Massachusetts Introduced Pests Outreach Project.

Identifying Asian giant hornets: The European hornet (Vespa crabro) is often confused for the Asian giant hornet. There are three main differences between these hornets:

Size The Asian giant hornet is slightly bigger than the European hornet (photos not to scale, enlarged for detail).
Stripes The Asian giant hornet has regular black-orange stripes along its abdomen; the European hornet has irregular brown-yellow stripes.
Head The Asian giant hornet has an orange head; the European hornet has a golden yellow head.

LEFT: Asian giant hornet, Washington State Department of Agriculture, Flickr
RIGHT: European hornet, Chris Moody, Flickr

To learn more about the Asian giant hornet, please read this USDA report instead of news articles. To learn more about how you can help mitigate the establishment of introduced species in general, check out these resources:

U.S. Department of the Interior, Invasive species: finding solutions to stop their spread
National Park Service, Invasive and non-native species: stop the spread
The Nature Conservancy, Invasive species: what you can do
Alliance for the Chesapeake Bay, 10 ways you can prevent the spread of invasive species

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Return of the honey bees

Isaac Weinberg

To watch my honey bee spring inspection click here!

Spring has sprung, and the bees and butterflies have begun their return to Medford. If you’re like me, you may have wondered why insect pollinators were gone in the first place. Cold temperatures and lack of flowering plants make New England winters an inhospitable place for insects, yet year after year they return. Different species use different strategies to get through the winter months. Monarch butterflies dodge the cold by migrating south for the winter. Bumble bee queens sleep through the winter in subterranean burrows. Other insects lay eggs in fall that remain dormant in winter and hatch in spring.

Honey bees are unique in that they are the only insect pollinator that is awake and active throughout the entire winter. They are able to do this because of their massive colony size of up to 50,000 bees. Honey bees bunch up in their hive like emperor penguins and spend all winter shivering by flexing their wing muscles to keep their hive warm. Even in the coldest months of winter, honey bees can keep the temperature of their colony above 90 degrees Fahrenheit! In order to have energy to shiver all winter, honey bees hoard pounds of honey and pollen in the summer and fall which they eat for energy over the course of winter.

a *Varroa* mite (visible in red) feeds on the fat body of a developing bee.

Recently, overwintering deaths of managed honey bee colonies in the US has been incredibly high, with almost 40% of colonies dying each winter. Over the winter it is very difficult for beekeepers to directly help colonies, since opening a hive and exposing it to the cold would be incredibly damaging. Because of this, many beekeepers to take an active hand in helping their bees in the early spring. The first cool days in spring are very dangerous. They have likely consumed all their food stores and, with few flowers yet blooming, there may be no way for them to restock. Spring is also when there are is an explosive increase in populations of Varroa destructor, a parasitic mite that latches on to honey bees and eats their fat bodies. In the spring it is often critical for beekeepers to supplement the nutrition of their colonies, and keep the mite population under control in order to have strong healthy hives during the year.

Honey bees get most of their nutrients from different flower products, they collect sugar rich nectar to make honey which adult bees use as their main source of energy, and protein rich pollen which is fed to larvae to help them grow. In order to help supplement the diets of bees, beekeepers can feed their colonies sugar solution, and synthetic pollen patties. One type of pollen patty is made using bee collected pollen and mixing it with a 1:1 sucrose:water solution until it has a clay like consistency. In the absence of pollen, other supplements like yeast, protein powder, and eggs can be mixed with sugar water to create patties. Patties can then be made available to the bees by simply placing them in the center of the beehive.

A pollen patty wrapped in freezer paper and placed in the center of a honey bee hive.

Next, many beekeepers treat for the mite Varroa destructor. Varroa is one of the biggest contributors to honey bee decline in the United States. The mite latches on to honey bees and feeds on their fat bodies, draining nutrient reserves, and spreading disease throughout a colony. The mites primarily target honey bee larvae, and reproduce by laying their eggs directly on honey bee brood. As honey bee colonies begin to rear large amounts of brood in spring mite populations also increase exponentially. For this reason, it is important to treat for mites before a colony begins its spring uptick in brood rearing. There are many ways beekeepers treat for Varroa, which vary both in their efficacy combatting Varroa and in their lethality to the honey bees themselves. One of the most common treatments are Apivar strips because they are easy to use, relatively benign for the honey bees, and deadly to the mites. The strips can be easily hung in a honey bee hive and paralyze mites, preventing them from feeding. Because the active ingredient in Apivar is an arachnicide, it acts on the spider-like mites without causing excessive harm to the honeybees, and also does not linger for long in the hive once removed.

Though winters are an energetically demanding time for honey bees, and the early days of spring can be dangerous with temperature fluctuations and limited flowers (especially in New England where we get snow in April!), beekeepers can take an active hand in ensuring colony success. By supplementing food in early spring, treating colonies for mites, and being careful to leave some honey for the bees during fall collections, beekeepers help their colonies start the year on a strong footing and remain healthy and productive all year round!