If you are a subscriber to our blog, you have likely seen our photos and videos of one of our favorite plant-pollinator interactions: the petals of Farewell-to-Spring (Clarkia amoena) being harvested by leafcutter bees!
After observing this eccentric harvest behaviorin the research garden, we got curious about the bees behind the petal-nest craft, and how we could study this interaction further.
Leafcutter bee mid-petal-harvest! Photo by Devon Johnson.
Crescent-shaped petal-cuts left behind by leafcutter bees.
iNaturalist is a popular community-supported biodiversity database that the Garden Ecology Lab has been experimenting with in recent years. Jen realized that the leafcutter bees’ distinct crescent-shaped mark are visible in many iNaturalist observations of Clarkia amoena. She wondered how we could use the already sizeable iNaturalist database of Clarkia amoena observations to study the interaction over a wider geographic and chronological scale than that of the research garden. Jen and Gail agreed to mentor me in producing an undergraduate research thesis on this subject.
The study’s objective is to use iNaturalist’s data on Clarkia amoena to see if there is a difference in leafcutter bee usage of Clarkia amoena petals based on whether the flower is a native versus a cultivar type, and whether the flower is found in an urban or non-urban environment.
In this process we have found that iNaturalist is easy for anyone to contribute to, but the information it provides is limited compared to the wealth of contextual information gained when being in the actual, living presence of a specimen. So, to get a greater feel for the intricacies of this flower, I embarked on what we called “Ground-Truthing Field Trips” to check out some Clarkia amoena populations in the “real world”.
I went out during peak pollinator season, following the coordinates of recently posted iNaturalist observations. Each specimen I visited was incredibly different from the next. I found the delicate blossoms in natural areas, the borders of farmland, restoration sites, and gardens.
Data from these trips will not be published in my thesis because the contexts are not exactly comparable, and my sampling was exploratory rather than precise. Nonetheless, I gained contextual insight and inspiration watching diverse pollinator assemblages in beautiful meadows of pink.
Mallory at a meadow restoration site near Corvallis with Clarkia amoena and tarweed (Madia elegans).
The field trips have helped us more clearly see through the window of iNaturalist and have informed the methodology we use.
For example, I saw examples of hybridization between two species of Clarkia in a seeded restoration site, and cultivar-hybrid escapees in natural areas. It’s been important to navigate identification of cultivars and hybrids in iNaturalist.
In a restoration prairie seeded with two different Clarkia species, pollinators cross-pollinate them, giving rise to sterile hybrids (Lewis & Raven, 1958). Note the malformed stigma and anthers.
Simultaneously, our field crew recorded petal-cutting behavior on the Clarkia amoena natives and nativars at Jen’s research garden this summer. Below are the three cultivars in the garden, and if you look closely you can see “petal-cuts” which we counted and recorded weekly. We will analyze the difference in leafcutter usage between the cultivars and native type.
‘Aurora’‘Scarlet’‘Dwarf White’
This hot pink, stripy Clarkia doesn’t look like either the native or cultivars we had planted!
Clarkia amoena is an annual that reseeds itself effectively, so last year’s seeds gave rise to this season’s blooms. To our surprise, however, Clarkia amoena of all different colors started popping up in our research plots this Spring! Last season’s bees had combined pollen from the garden’s varieties bringing rise to all sorts of intermediate forms.
Clarkia amoena is prone to hybridization between members of the species or cultivars in the same proximity. These intraspecific hybrids are fertile. We seek to explore how cultivar genetics may be moving into natural populations.
Through the winter, our team is working with the iNaturalist data to quantify leafcutter bee petal usage.We expect to share our results in June 2023, so stick around to hear about our findings!
Work Cited:
Lewis, H., & Raven, P. H. (1958). Rapid Evolution in Clarkia. Society for the Study of Evolution, 12(3), 319–336.
The sunny days are diminishing as summer rolls into autumn, and as the sun descends, the bees’ flight lulls to rest. Bees sense and respond to light and use the sun to orient themselves and navigate. Along with their two large compound eyes that are used for vision, bees have three simple eyes that sit atop their their heads in a triangular formation. These are called ‘ocelli’ and they sense light.
Originally posted by postgraduate student Hamish Symington, this video shows bees being studied by fellow student Kristina Buch in the Cambridge University Botanic Garden.
Ocelli can be seen atop the head between the compound eyes. Photo of bee from the genus Triepeolus by Mallory Mead.
There is a video circulating the internet of honeybees flying in an enclosure in a laboratory. The video shows the researcher turning off the lights in the enclosure, causing the bees to drop to the ground instantaneously, showing how honeybees will not fly in the absence of light.
We notice similar behavior in the field on days where clouds pass over the sun intermittently. When the sky is bright, our plants bustle with pollinators, and when shadows come over, most bees are suddenly out of sight. It makes sense that as the days get shorter and colder the sight of pollinators will become more and more fleeting!
Some bees are still coming out during the warm October afternoons, and collecting their final energy reserves for the winter. Goldenrod, Douglas’ aster, California poppy, bee balms, and black-eyed Susan, amongst other late blooming pollinator plants are still providing bees with nectar and pollen during this time of transition.
Purple Aster and goldenrod in a natural meadow. Photos by Mallory Mead.
Goldenrod in meadow.
A long horned bee and a sweat bee on black-eyed Susan (Rudbeckia hirta).
Metallic green sweat bee on Scabiosa.
During this season, honeybees and bumblebees predominate the landscape, while long-horned bees (genus: Melisoddes), leafcutter bees (genus: Megachile) and sweat bees (family: Halictidae) can still be seen as they finish up resource collection in the Willamette Valley.
Social bees
Honeybees must make enough honey before temperatures drop and they can no longer leave the hive, so you’ll find them foraging for pollen and nectar as late in the season as possible.
In late summer and fall we begin to see an influx of bumblebee queens. During the summer, the queens are busy reproducing in their underground hives, while worker bees take to the landscape. However, near the end of the foraging season, new queens hatch and fly out to find mates and food. You may see bumblebee queens getting their last bits of food energy before overwintering, while the rest of the colony (males and workers) dwindle away.
Leaf, mud and petal nests are capped and ready for winter! Photos by Mallory Mead.
Petal nest in bamboo.
Many solitary bees are finishing their last nests where they’ve laid eggs for the next generation of their species.
If you care for nest boxes in your garden be sure to take appropriate steps to bring your bees indoors and clean their cocoons. Check out the Linn Master Gardener Association Bee Notesemail list to receive timely emails about the seasonal steps of caring for mason bees.
When solitary adult bees finish reproducing and nest building, their work is done, so they die off. But small carpenter bees, from the genus Ceratina, are an exception. Ceratina females remain as late into the cold season as they can muster in order to guard their nests.1 These protective mothers fend off predators, pests and parasitoids that try to invade the nests.
This fall, we hope you are able to see some of the last glimpses of bees of the year!
This post concludes our series on what the bees are doing right now! Thank you for taking part in this seasonal journey through the lives of bees in the Willamette Valley.
Source Cited:
1: Danforth, B. N., Minckley, R. L., & Neff, J. L. (2019). The solitary bees: Biology, evolution, conservation. Princeton University Press.
A syrphid flying over a clarkia, photo by Devon Johnson
We have been seeing syrphid flies (family: Syrphidae) in great abundance this summer over at the Garden Ecology lab’s research garden, so much so, that our field research team has begun to call it the year of the syrphids! These bee-mimicking, skittish pollinators have particularly loved the native and cultivar yarrow we have planted in our plots. Although their abundance has recently dipped–likely because Yarrow (Achillea millefolium) is done with its first round of bloom–we still see them buzzing around.
Syrphid flies, also known as flower flies or hover flies are a common visitor of gardens. You may see them buzzing around bright flowers or fighting mid air. They are important pollinators and feed off of nectar and pollen in their adult stage. Additionally, in their larval form, they are great at reducing aphid populations, but are extremely susceptible to pesticides.
Line drawing of Toxomerus spp. life cycle, credit to Brett Blaauw, Department of Entomology, Michigan State University
The life cycle1 of syrphids start with the adults laying eggs in leaves of infested plants. After about three days, they hatch into their voracious, blind, larval stage.
The larvae feast on small pests like aphids, leafhoppers, scales, and thrips. The larvae do this by moving along plants, lifting their heads to try and seize and pierce their prey with their triple-pointed dart inside their mouth2. After slurping their prey dry, they will discard the exoskeleton.
Larvae will develop through a few instars and after 1 to 3 weeks will go into a pupal stage on the host plant or on the soil. After two weeks, an adult emerges.
Syrphid larvae with an aphid in its grasp. Photo by Oregon State University
In the pacific northwest, our common syrphid is Scaeva pyrastri. It is unique in that rather than overwintering as a larvae, S. Pyrastri overwinters as an adult. Three to seven generations occur in a year, with possibility for the higher counts depending on the region and species. Another species, originally native to Europe, the drone fly (Eristalis tenax3) is named after male honey bees because it is mimics them so well. Other mimics in Syrphidae lay their eggs in the nests of bumblebees or social wasps, where the larvae eat dead bees and detritus.
Their quick movements and bee-like appearance can make syrphid flies hard to identify.
To identify a flying insect as a syrphid, look for a single pair of wings. Flies (Order: diptera) do not have a second pair of wings like bees. Instead they have a vestige of hind wings called halteres that look like little nubs beneath their wings. These act like gyroscopes to help the fly balance during unique in-flight maneuvers. Also look for large, forward facing compound eyes typical of any dipterans. In our lab, we’ve see a wide range of size and different colors. Syrphids can be anywhere from a tenth of an inch to half an inch long, and have black or brown bodies with white or yellow spots and stripes. Fun fact: most hover fly mouths are extendable ‘sponges’ that mop up nectar and pollen.
Common oblique syrphid (Allograpta obliqua). Notice the nub-like halteres below the wings. Photo by Ron Hemberger
Flower flies are extremely important to pest control and pollination, 40% of syrphid species larvae feast on the previously mentioned prey, and each larvae can eat up to 400 aphids during development!
Unfortunately, the larvae of syrphids are similar to many other species so are hard to identify. However, they are usually on pest infested plants and may be seen near adult syrphids. Look for their typical ‘stretching’ behavior while they are on the hunt. If you have a pest problem, avoid using pesticides or insecticides! These kill the syrphids that can help with pests. Instead, promoting syrphids or other pest eaters like ladybugs and lacewings by providing a variety of insectary plants can help you in the long run.
A large syrphid on our native yarrow, with a threat nearby! Photo by Devon Johnson
As previously mentioned, yarrow (Achillea millefolium) has been our most successful syrphid-attracting plant in our lab this year. Syrphid flower preference varies based on the subfamily, according to studies. The subfamily Eristalinae is attracted to white flowers, Pipizinae prefer white and yellow, and Syrphinae is more general. Link to an article going more in depth on syrphid flower preference here4.
Not coincidentally, native yarrow is primarily white, while our cultivars are yellow and pink. Observationally, syrphids visit yellow yarrow at a similar rate as they do the native, while our pink cultivar saw next to no syrphid visitors. We recommend planting yarrow as well as a variety of native flowering plants to support these pollinators. Leave leaf litter and debris around flowering plants, too. These provide protected overwintering sites which syrphids rely on7.
Syrphid on our yarrow ‘Moonshine’ cultivar. Photo by Devon Johnson
Currently, no syrphid species are on the U.S. Endangered Species Act lists, but like many insects, this underappreciated pollinator is understudied and biodiversity of this group is not well tracked. In Britain, however, some hoverflies have been placed on their Biodiversity Action Plan.6
Whether syrphids are endangered or not, we can help biodiversity by promoting native pollinators and planting native plants in our yards and gardens.
We are entering the heart of summer, with blue skies, rising temperatures, blooming flowers, and growing gardens. As some of us are taking this time to relax in the bounty of our gardens and in whatever shade we can find, our pollinator counterparts are in the middle of their busiest season. The pollinators are out in full force, and it seems almost impossible to turn around in a garden without spotting a new butterfly, bee, or beetle. So for those among us who want to engage even further with the friends visiting our gardens around this time of year, we have the perfect game for you: Pollinator Bingo!
Our Pollinator Bingo-or should we say BEEngo- is a healthy mix between Bingo and a scavenger hunt!
Here’s how to play:
Select the Bingo Card you will use
Download it, or print it out, and get it ready to be filled out
Keep your eyes open for these visitors in a garden. When you spot a pollinator on your Bingo card, mark that pollinators square.
Once you fill an entire row (horizontal, vertical or diagonal) you’ve won your BEEngo!
Extra Credit Challenge: Try to black out the entire card!
We hope you have fun playing Pollinator Bingo outside, exploring and enjoying the natural world in some way. Good luck BEEngo players!
Below, we included some pollinator spotlights, so you can get to know some of the species on your Bingo card a little better!
Pollinator Bingo Spotlight List:
Tribe Eucerini, Longhorned bee
Eucerini, also known as long-horned bees, are favorites among our lab members. They are the most diverse tribe in the family Apidae, with over 32 genera. These bees are solitary and ground-nesting. What makes them distinct and a lab favorite are the long antennae the males are known for and from which they get their common name. The females are also recognizable, as they have long hairs, known as scopae, on their hind legs, giving them the appearance of wearing very thick pants.
Photo by Svea Bruslind
2. Species Papilio machaon oregonia, Oregon Swallowtail butterfly
As with any in the Swallowtail family, Papilio machaon oregonia, or the Oregon Swallowtail, is big, beautiful, and eye-catching. It was officially named Oregon’s state insect on July 16, 1979. It is native to the northwest and is only found in Oregon, Washington, Idaho, and sections of British Columbia. For the purposes of Pollinator Bingo, any Swallowtail will count for its space. Keep an eye out for the Oregon Swallowtail and others, and see how many different species you can find!
Photo by Cara Still
3. Family Syrphidae, Flower Fly
Hoverflies, flower flies, and syrphid flies are all different names for the flies within the family Syrphidae. Syrphid flies come in a wide variety of sizes and colors, with some that resemble wasps and others that look nearly identical to bees. Most syrphids, however, can be found with some kind of striping on their abdomen. Syrphids are essential to any garden as they help with pest control and pollination. Some people are surprised that flies are pollinators too, but hopefully, this list can illustrate the wide variety of pollinators out there!
Photo by Devon Johnson
4. Species Trichodes ornatus, Ornate Checkered beetle
Trichodes ornatus, or the Ornate Checkered beetle, is an interesting species, as during the early stages of its life, instead of pollinating, it feeds on pollinators. These beetles will lay their eggs on plants such as yarrow, sagebrush, and asters. When these eggs hatch, the larvae attach themselves to a visiting bee, usually a leafcutter bee. They will then be transported to the bee’s nest, where they will eat the provisions left there for the host larvae before eating the host larvae and burrowing into nearby cells to do the same. As an adult, the Ornate Checkered beetle will feed on pollen but will not miss an opportunity to snack on other visiting pollinators when foraging for pollen.
Calypte Anna or Anna’s hummingbird should be a familiar sight for many of us. This rambunctious bird is a permanent resident along the Pacific Coast, staying year-round through winters instead of engaging in migration as other species of hummingbirds are known to do. Males of Anna’s hummingbird are pretty talkative, often vocalizing with a buzzy song. The males have a brilliant red head with a green body, and the females have similar green plumage, but without the red coloration on their face and neck.
Summer is the main active season for many bee species. After a wet spring in Western Oregon, the sun is out and our world is in bloom!
So what are summer bees up to right now? The main events of the season are…
Foraging for nectar and pollen
Finding mates and laying eggs
Excavating, finding and building nests for offspring.
Adult bees also experience predation by spiders and birds during this time. This Crab Spider caught a female long horned bee in its jaws!
A female long horned bee caught by a crab spider on Douglas’ Aster.
So who exactly is out and about in your garden at this time of year?
Bumblebees and honeybees visibly dominate the landscape throughout the summer, but lean in closer to your flowering plants and you’ll find the smaller sweat bees (family: Halictidae), long horned bees (genera: Melissodes and Eucera), leafcutter bees (genus: Megachile) and small carpenter bees (genus: Ceratina). Although there are many others amid the vast diversity of bee species science is only beginning to understand, these are some common garden visitors. We’ll go through each group and their summer activities.
Notice the two adomenal segments beneath the yellow stripe of this male yellow-faced bumblebee(Bombus vosnesenskii). Photo by Jen Hayes.
The presence of pollen on a bee especially carried in pollen baskets, is a good indicator that the bee is a female. Photo by Jay Stiller-Freeman
Bumblebees: By summertime, most queens have established colonies of workers who do the foraging for the hive, so we see less large queen bumblebees and more smaller workers as the season progresses. Later in the season, queens lay male eggs as well as eggs for the next generation of queens. Male bumblebees take to the landscape in mid to later summer, recognizable by their additional segments on their abdomen, long antennae, and by the fact that they don’t carry pollen like females do. Males do not have stingers, so if you can confidently identify male bumblebees, they are fun to play with while they’re waiting around for new queens with which to mate. You’ll find them sipping on nectar-rich plants like lavender, herbs, asters and heal-all.
Honeybees: Summer is prime time for honeybees! Worker populations are at their peaks; pollen and nectar are flowing. As hive population size rises and available hive space remains static, honeybees may organize a swarm. In this process, the current queen lays new queen eggs and part of the colony joins her to lift off and leave the colony in search of a new cavity to make their home. Swarming is considered a form of colony-level reproduction supporting the idea that honey bee colonies are super organisms. Swarming is common in spring and early summer. Beekeepers add new boxes to hives so prevent their colonies from swarming.
Late summer is mating season for honey bees. Males and new queen eggs are laid and emerge to mate with individuals from other colonies. Honeybees mate in the air at heights ranging between 15 and 60 m1.
A yellow-faced bumble bee and a honey bee sip nectar from lavender. Photo by Devon Johnson.
Sweat bees
Sweat bee on California Poppy ‘White’. Photo by Tyler Sato Spofford.
A halictid dear to our hearts at the Garden Ecology Lab is the metallic green bee (genus: Agapostemon). While females provision nests in the soil, you can find males resting in congregations on flowers in the evening time and early morning!
Sweat bees are one of the most common groups of “small” bees you’ll find in your garden. They forage on a wide variety of plants and come in a wide range of sizes, but most have striped abdomens, and all carry pollen on their hind legs and nest in soil.
Agapostemon virescens male congregation.
A male long horned bee from the genus Eucera on a California Poppy ‘Purple Gleam’. Photo by Jen Hayes.
Long Horned bees
Long horned bees are most active on our research plots in the mid to late summer. I love this group because they are so easy to recognize. Males have antennae that are way longer than other bees’ relative to their bodies. The females, who bear antenna of normal lengths, are still easy to spot because they have long feathery scopa (or hairs) on their hind legs for collecting pollen that they absolutely pack with pollen while foraging.
Long horned bees are sometimes referred to as “sunflower bees” for their love of foraging on sunflowers.
Long horned bees nest in the soil2, so when you see them take it as a reminder to leave some uncovered, undisturbed soil in your garden for these bees to persist!
Notice this female long horn’s feathery pants! Photo by Mallory Mead.
A relatively large small carpenter bee. Photo by Mallory Mead.
Small Carpenter bees
When I point out small carpenter bees (genus: Ceratina), most of my friends can’t believe they are bees. They think they are some kind of flying ant. Their bodies are sleek, and often shimmer with a green or blue reflective gleam.
Small carpenter bees are considered wood excavators as they dig out the pith from dry plant canes for their nests. Ceratina are a unique group in terms of their parenting style. Unlike other solitary bee mothers, Ceratina mothers guard their offspring even after their offspring have developed into adults. Mothers stick around as long as they can until Winter falls.2
Leafcutter bees
Leafcutter bees (genus: Megachile), as their names suggest cut leaves from their host plants! They use these bits of leaves to line their ground and cavity nests, to waterproof and protect their offspring.
Leafcutter bees are from the bee family Megachilidae, a family known for creative nest building. Bees in this family were supposedly able to expand their ranges due to their flexibility in nesting site and material. They’ve been found nesting in wood, porous stones, stems, galls, and even snail shells filling these various cavities with leaves, mud, plant resins, pebbles, straw and even petals2. The fascinating nest building behavior we’ve gotten to witness in the field is petal cutting of Farewell-to-Spring (Clarkia amoena) blooms.
We can track the usage of Farewell-to-Spring petals by leafcutter bees due to the signature crescent shape left behind on the flowers.
Thank you for joining us on this exploration of some of Oregon’s summer bees and what they are currently doing! We will release one more blog post in this series. Be sure to subscribe so you don’t miss the next in the series!
Happy pollinator week and first official week of summer! ☀️🐝🦋
Pollinator week is an annual celebration in June to emphasize the importance of pollinators and their health, started by the Pollinator Partnership. To celebrate pollinator week, we’re going to share some information with you about a few of our favorite pollinators and a few others deserving recognition. June is also Pride Month, so we are going to start with a fun fact connecting pollinators and Pride! 🌈
Did you know there are pollinators named after drag queens? A new genus of soldier flies were discovered in Australia 2020 and given names that are indicative of their metallic and rainbow-colored bodies! Among Opaluma fabulosa, O. iridescens, O. opulens,O. sapphira and O. unicornis are O. rupaul, named after the drag queen RuPaul, and O. ednae, named after the Australian drag queen Dame Edna.
Soldier flies belong to the Stratiomyidae family, which include many flower-visiting flies! Many adult soldier flies visit flowers for nectar and subsequently transfer pollen on their bodies as they travel from one bloom to the next. Six of these seven Opaluma species were impacted by the Australian bushfires in 2019 and 2020; their recent taxonomic identification will allow them to be monitored in recovery efforts following the fires. The full citation for these stunning soldier flies can be found here.
To stay on the theme of iridescence, next we will share some information about my (Jen’s) favorite pollinators: Orchid bees! Orchid bees are in the same family as bumblebees and honey bees (Apidae) but are found within their own tribe, Euglossini. Within Euglossini, there are only five genera: Algae,Euglossa, Eulaema, Eufriesa, and Exaraete. Only one species of orchid bee is found in the United States (Euglossa dilemma), with the majority being found in Central and South America.
Euglossa sp. Eulaema sp.Photos by Jen Hayes, taken at La Reserva Inti Llacta in Nanegalito, Ecuador
Not all orchid bees are iridescent– bees from the genus Eulaema are the exception, which are more similar in appearance to bumblebees than they are to the metallic members of Euglossini. I find orchid bees to be mesmerizing, not only because of their novel color forms, but also their unique adaptations. Some orchid bees’ tongues (proboscises) are more than 1.5 times their body length in order to access nectar located in long, tubular flowers! These bees often fly with their proboscis tucked under their body, and it may look like a small tail as it trails past their abdomen.
Euglossa have highly modified tibias on their hind legs. Male members of Euglossa species have a “pouch” on their tibia, used to collect and store floral fragrances from flowers in the form of essential oils. These oils are later used to attract potential mates. I like to think Euglossine males would be excellent candle makers.
Mallory’s favorite pollinators are long-horned bees, in particular those from the genus Melissodes, which are highly abundant in the latter half of our field season! Mallory loves long-horned bees because they have many traits that make them easily identifiable in the field. Males have elongated antennal segments which are indicative of their common name ‘long-horned’. They often have interesting colored eyes as well- some of the specimens we collect have green, blue or grayish eyes that contrast greatly with their often blond-colored hair (scopa). Her favorite trait, however, is the scopa on their hind legs. When full of pollen, long-horned females often look like they have ‘pollen pants’ on, in contrast to the neat and tidy pollen baskets seen on bumblebees! Svea thinks their pollen pants make long-horned bees look like they’re wearing a pair of western-style chaps. Melissodes primarily pollinate species from the Asteraceae, with specialization occurring on asters, daisies, and sunflowers. Sometimes Melissodes are called ‘sunflower bees’.
Melissodes sp. visiting a cosmo, photo by Mallory Mead.
Svea’s favorite pollinator is Anna’s hummingbird (Calpyte anna). C. anna is one of seven hummingbird species native to Oregon. Svea enjoys watching Anna’s hummingbird as a pastime at her parents’ house: they have a small, active community of hummingbirds that are very vocal and can be seen fighting over their nectar sources (including their butterfly bush and hummingbird feeder).
Svea also mentioned that the males are particularly pretty, though it requires a particular angle of light to make their iridescent copper-red colored throats glow. The ‘Anna’ in Anna’s hummingbird comes from the French Duchess of Rivoli, Anna Masséna, who was part of the court of France’s last empress (Eugénie de Montijo, 1853-1870). Anna’s hummingbirds are important pollinators in California, where they feed from coastal chaparral flora that share a similar phenology (breeding and feeding patterns) with the pollinator.
Nicole is another member of the lab whose favorite pollinator is a hummingbird! Nicole’s favorite pollinator is the Rufous hummingbirdSelasphorus rufus. The USDA Forest Service describes the Rufous hummingbird as “small but feisty long-distance migrant[s]”. They are small in size and feisty in their protection of their feeding territories, they have been known to chase off other hummingbirds, large insects, and even people! Some of their preferred host plants include morning glory (Ipomoea arborescens), ocotillo (Foquieria spp.), shrimp plant (Justicia spp.) and red-colored blooms from the mint family, such as Salvia elegans and Stachys coccinea. Nicole loves the Rufous hummingbird because she regularly saw them while she was growing up. They could regularly be seen foraging and defending their territory in her parent’s yard.
Cara’s favorite pollinator is the Western Tiger Swallowtail Papilio rutulus. This magnificent butterfly can be commonly found at Cara’s research plantings of butterfly bush (Buddleja spp.), and can also be spotted basking on yarrow or slowly fluttering along the hedgerows at Oak Creek Center for Urban Horticulture. Despite the name ‘butterfly bush’, Cara has found butterflies to be infrequent visitors of Buddleja, though of the few butterfly visitors they receive, the Western Tiger Swallowtail is the most common. Cara additionally grew up seeing swallowtails every summer, which is why they are her favorite pollinator! To read more about this swallowtail, check out Lucas’s Pollinator of the Week Post.
It’s early spring and the trees have begun leafing out. Colorful flowers are springing from the ground, and the landscape is slowly coming to life with insect activity. In this post, I’ll highlight some of Oregon’s ubiquitous spring bees, what they are up to, and how to easily recognize them.
Graphic by Jen Hayes
Queen bumblebees are emerging from their winter burrows under leaf litter and forest duff. They zoom by with boisterous buzzes. Queen bumblebees are sturdy and furry, and can power through wind, rain and cold better than any other type of bee. Queens are much bigger than the workers that will come once the queens find nest sites and begin laying eggs. For now, they work alone, preparing to lay their first set of worker eggs.
If you see (or hear) any queen bumblebees this spring as they scan the sparsely blooming landscape, they are most likely looking for a proper nest site, finding nectar to energize this search, or, if one has already found her nest, she may be collecting pollen to feed her developing worker offspring.
A rain-drenched Yellow-faced bumble bee on Oregon Grape. Photo by Jen Hayes.
A female mason bee has brought bright yellow pollen to her nest. Video by Jen Hayes.
Mason bees (Osmia lignaria) are a cherished Oregon spring bee active from March to early June. Look closely in a bee hotel for a chance to observe mason bees in action!
Male mason bees emerge first from their pupal cocoons. You might see them patrolling bee hotels waiting for a female to chase down. When the females emerge a little later, they mate and then begin their work provisioning nests with pollen balls and eggs. An individual female has a short lifespan living only about 20 days, but in this time, she may provision anywhere from 2 to 7 nest holes each containing many offspring cells.1 Quite the busy bee!
Andrena is a genus of mining bees that are some of the earliest risers when it comes to spring emergence. They are a diverse group of small, furry, ground-nesting bees that are only active for a few weeks out of the year. Andrena are solitary bees, but can be seen foraging and mating in droves on early blooming fruit trees like cherry, apple and pear. Last spring, I watched hundreds swarm this cherry tree to collect nectar and mate.
Andrena in cherry tree (captured with magnifying lens). Photo by Mallory Mead
Andrena mating pair. Photo by Mallory Mead.
Spring Bee Quick ID:
Now, let’s identify some of the bees you may see out and about on sunny spring days when the wind is low. We’ll start with the most conspicuous group – the bumblebees. Bumblebees are the biggest and the loudest bees on the landscape, covered in a thick coat of fuzz. Here’s how to recognize the 3 most common species of bumblebees you’ll see in the Willamette Valley in early spring.
Bombus vosnesenskii or the “yellow-faced bumblebee” is by far the most common bumblebee in this region. It is recognized by the yellow fuzz on its face and yellow band near the distal end of its abdomen.
B. vosnesenskii foraging on butterfly bush. Photo by Mallory Mead.
B. melanopygus queen foraging on Wartleaf Ceanothus. Photo by Mallory Mead.
Bombus melanopygus, the “black-tailed bumble bee” is another of the earliest Bombus species to emerge. You can identify this bee by the orange band in the middle section of its abdomen!
Bombus mixtus, the “fuzzy-horned bumblebee”, tends to emerge a little later than the previous two species, and has orange hair on its lowest abdominal segments.
B. mixtus flies amid borage plant. Photo by Mallory Mead.
Mason bees can be recognized by their deep iridescent blue-green color, that sparkles in the sun. Males are distinguished from females by their small size and the yellow mustaches found on the front of their faces. Females lack the yellow tufts and are larger than the males but smaller than a honey bee. They carry pollen on the underside of their abdomen which is a trait unique to their bee family, Megachilidae.
Female mason bee. Photo by Jen Hayes.
Male mason bee. Photo by Mallory Mead.
Andrena are a diverse group that are tricky to identify. They can be distinguished from other small, furry bees by the presence of velvety hairs between their eyes and the middle of their face called “facial fovea”.2
They also carry pollen on their hind legs and on hairs between their abdomen and thorax, which distinguish them from bees in the Megachilidae family.
We hope this little guide will help you experience the native bees in your landscape this spring that make the pollen go round.
Thank you for joining us on this exploration of Oregon’s spring bees and what they are currently doing! We will release two more blog posts in this series, one for each of the four seasons. Blogs will be posted during their prospective seasons, so be sure to subscribe so you don’t miss the next in the series!
Welcome to the Garden Ecology Lab’s “What are the bees doing” mini-series! This series will extend through the four seasons to shed some light on where bees are in their life cycle and what they may be doing during each of the four seasons. We begin with winter, and an overview of the overwintering and nesting strategies of common groups of bees in the Pacific Northwest.
Graphic by Jen Hayes
As the seasons change, where do all the bees go? Different groups of bees utilize unique strategies to survive the cold of winter. In many cases, bees require cold temperatures to develop properly, and as spring rolls around, they rely on thermal cues to determine when to start their next phase of life.
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We can divide bees into four broad categories based on their strategy to nest and survive the winter. There are the Ground Nesters – who find or dig in the ground to nest and lay eggs, Cavity Nesters – who nest in hollow reeds, canes, or in people’s backyard “bee hotels”, Bumblebees – whose new-born queens burrow into leaf litter, waiting to start a colony in spring…. and then there is the oddball: the European Honey Bees, who are not native to North America, but were brought here along with European colonizers and are now key players in modern agriculture. They do things pretty differently than our native bees, so we’ll start our discussion with them.
The European Honey Bee
European honey bees (Apis mellifera) survive the winter huddling in their hive! They are an example of a social insect and many consider a honey bee hive a superorganism. Fueled by their honey stores, the colony huddles together in a mass to thermoregulate at temperatures between 33 – 36°C (91.4 – 96.8°F).1 I love these words from the American Bee Journal:
"The honey bee is a cold blooded insect; but the honey bee colony is a warm blooded creature."1
We will see that honey bees are the only bee in our landscape to overwinter socially. The rest go it alone.
Bumblebees
A Bombus californicus queen on Comfrey (Symphytum sp.) in early Spring. Photo by Mallory Mead.
Bumblebees are social bees too, living in natural cavities most often in the ground, but in winter, the members of the colony die off except for the new-born queens. These queens will fly out of the hive on her maiden voyage to mate with a male bumblebee before finding a place to settle and overwinter alone.
Queens find a safe environment often a few inches deep under leaf litter or light soil. As temperatures decrease in Fall and early Winter, the queens do not thermoregulate. Instead, they enter diapause, which is a state of arrested development. An overwintering queen appears frozen in the soil until warmer temperatures wake her again. In the late Winter or Spring she will begin looking for a site to start her own colony.
Cavity Nesting Bees
About 30% of native bees are cavity nesters who build their nests inside cavities in wood or reeds.2 These bees avoid overwintering as adults, and instead, they lay their eggs in cavities and die before the winter temperatures come.
Female cavity nesting bees forage for pollen and nectar and nesting materials in the spring or summer and make balls of pollen and nectar (often called “bee bread”) as food for their offspring!
They lay eggs on the pollen balls, and then proceed to seal off compartments, one for each of the eggs, until the cavity nest is full. These eggs will hatch into larvae that consume the bee bread as winter approaches.
Bee nests in bamboo sticks, indicated by the mud caps at the front of the stakes. Photo by Gail Langellotto
Video by Oliva Honigman.
Here is a video of a small carpenter bee larva eating its bee bread, magnified under a microscope!
Once the larvae finish off their food store, they may spin themselves a cocoon in which they further develop into pupae. Cavity nesters spend the winter developing from pupae to young adults in their cocoons. These developing bees go into a state called torpor to survive the winter, where the bee is inactive and its body temperature drops, but it still goes through critical physiological processes and development.
These bees must experience low Winter temperatures natural to their region to undergo proper development. Mason bees, for example, have lower survival and vital rates when exposed to warm nest temperatures that simulate predicted climate change temperatures for their region.3
Empty mason bee cocoons that were removed from cavities for an experiment, and a newly emerged male mason bee. Photo by Mallory Mead.
Mason bees (genus: Osmia) are cavity nesters that have become well known in garden and agriculture circles in recent years, but many other groups of bees fall into this category too including leafcutter bees (family: Megachilidae), small carpenter bees (genus: Ceratina), large carpenter bees (Genus: Xylocopa),and masked bees (family: Colletidae).
A friend of the lab, Olivia Honigman, conducted a brief research project on small carpenter bees in Vermont. Here are some photos from her study that showcase a tiny cavity nesting bee, from the genus Ceratina, nesting in raspberry canes.
Ceratina larva in a raspberry cane. Photo by Olivia Honigman.
Ceratina larva and pollen ball under a scope. Photo by Olivia Honigman
Developing Ceratina pupae. Photo by Olivia Honigman.
Ceratina sp. flying into raspberry cane nest. Photo by Olivia Honigman.
Ground Nesting Bees
Last but certainly not least are the ground-nesting bees which make up about 70% of native bee species! Bees from the genera Andrena, Lasioglossum, and Halictus fall into this category.4 Ground-nesters have unassuming nests that are hard to spot, but under the soil, they are putting down bee loaves and laying eggs in a compartmentalized fashion, just like cavity-nesters!
Similarly, adult ground-nesters die after they finish provisioning their nests for their offspring. In the winter, the young bees of the new generation are developing from pupae into adults in their underground nests.
Left: exposed soil revealing tiny holes- could these be bee nests? Top right: A ground-nesting bee pokes its head out of its home. Bottom right: The entrance to a ground-nesting bee’s home.Photos by Gail Langellotto.
Although their nests are modest, some of Oregon’s showstopper bees fall in the ground-nesting category, such as the metallic green sweat bees (Agapostemon).
Metallic green sweat bee on a Clarkia flower. Photo by Mallory Mead.
Long-horned bees from the genera Melisoddes and Eucera also flaunt unique forms with noticeably fluffy, feathery hair on their legs they use for collecting massive volumes of pollen!
A female long-horned bee with dense hairs or scopa on her hind legs. Photo by Mallory Mead
This long-horned bee has “pollen pants” Photo by Mallory Mead.
To invite these bees to your garden, leave patches of earth free from wood mulch and instead mulch with compost! To avoid disturbing ground nests, avoid tilling when possible.4
Something remarkable about nesting in the ground is that, depending on nesting depth, ground nesters are more buffered from extreme temperatures than honey bees and cavity nesters whose homes may be in the direct sun. This may be a critical difference when it comes to surviving climate change.
Changing Climatic Norms…
With climate change upon us, native bees have experienced warmer than usual winter temperatures. These conditions may be suboptimal for their development and survival and encourage bees to emerge earlier in the season. Cavity and ground nesting bees require low temperatures with which they have evolved to reach physiological benchmarks for their development, and scientists worry that there will be phenological mismatches between plants and their pollinators in which bees emerge at different times than when their optimal food sources are in bloom as plants and insects will experience novel timing of thermal queues under climate change predictions.5
As bees and other pollinators face a multitude of challenges, we should support our local bees and appreciate them while we can!
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Thank you for joining us on this exploration of what bees are doing during the winter! We will release three more blog posts in this series, one for each of the four seasons. Blogs will be posted during their prospective seasons, so be sure to subscribe so you don’t miss the next in the series!
The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Douglas Aster!
The Garden Ecology Lab is releasing a series of plant profiles of the top 10 Oregon native plants for pollinators, based on Aaron Anderson’s 2017-2019 field trials of 23 Oregon native plants. We will feature one plant per week for 10 weeks, this is week 10, which marks the end of our 10-week series! Profiles will include photos, planting information, and will highlight common pollinators of each plant.
Melissodes visits Douglas Aster. Photo by Tyler Spofford.
Plant Facts
Scientific Name: Symphyotrichum subspicatum
Life Cycle: Perennial
Growth Habit: Vigorous spreader, spreads through underground rhizomes
Bloom Duration: July-November
Hardiness Zone: 6-9
Special Traits: Drought tolerant, deer resistant
When to plant: Starts can be planted in the spring or early fall.
Pollinator Facts
Douglas aster provides both nectar and pollen to its insect visitors.
Aaron’s research found three species of long-horned bees (Melissodes robustior, M. lupinus, and M. microstictus) and three species of bees from the family Halictidae (Halictus ligatus, Agapostemon texanus angelicus and A. virescens) to be associated with Douglas aster.
Other common visitors to Douglas aster include syrphid flies and northern checkerspot butterflies! Douglas aster may also be a larval host to 8 different month species1.
Douglas aster is native to Western North American with a range extending from Alaska to California. It has an impressive ability to spread and a high volume of flowers that buzz with pollinator activity throughout its long bloom season. Hosting a high abundance and diversity of bee visitors, Douglas aster is a pollinator plant superstar. It is particularly valuable as a late-season pollinator plant, able to provide both nectar and pollen to its visitors when these resources may otherwise be scarce in the landscape.
People often have strong reactions towards Douglas Aster – they either love it, or find it to be “weedy” in appearance. We hope that this highlight may help some people change their opinions about it! We in the Garden Ecology Lab love Douglas Aster for its abundant blooms in varying shades of purple and for its great capacity for supporting wildlife. In the late summer, we love watching the diversity of pollinators bouncing from one flower to the next! Some common visitors to Douglas Aster that we see at Oak Creek Center for Urban Horticulture include bumblebees, green bees, long-horned bees, small sweat bees, and butterflies, including the woodland skipper (pictured below) and the occasional grey hairstreak (Strymon melinus).
Here, we see a woodland skipper (Ochlodes sylvanoides) foraging from Douglas Aster!
Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.
Did you know?
By mid to late summer, Douglas aster is quite the frenzied pollinator feeding ground, making the Oak Creek team’s sampling effort always a bit of a challenge. These photos are from 2 years after these plants were established, so you can see just how full these young plants can get when grown in favorable conditions!
At Oak Creek, we started all of our Douglas Aster plots with 4x 4″ pots, planted in the spring of 2020. As you can see in the photos below, they easily filled up their 1×1 meter beds! If you’re worried about Douglas Aster taking over your garden, consider starting with a single plant and observe it over the season to see how it reacts to your garden environment. Aggressive spreaders can be used to fill spaces such as borders with forest edges or along fences where low maintenance plants are key. If you want to contain your asters, consider planting some in a large pot or in an area where you can easily control the spread of their underground rhizomes. The purple flowers contrast beautifully with other late season natives, such as goldenrod and Madia.
Jen standing next to her Douglas Aster experimental plots. Photo by Tyler Spofford.
Tyler vacuum sampling bees off of a Douglas Aster plot. Photo by Jen Hayes.
Photos from the field
A yellow-faced Bumblebee visits a Douglas Aster flower
A woodland skipper enjoying some nectar
The baby Douglas Aster plants we introduced into the field in 2020
Douglas Aster still blooming strong on October 3, 2020
The native Douglas Aster has beautiful purple rhizomes!
Douglas Aster cultivars are even more vigorous, look at all these new shoots we removed from a neighboring plot!
Douglas Aster 1 year after planting, with last season’s biomass removed
A sweat bee enjoying some pollen!
Thanks for tuning in to the last posting of our Pollinator Plant PR Campaign! We hope you try growing some of these fantastic pollinators plants.
The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. California Poppy!
The Garden Ecology Lab is releasing a series of plant profiles of the top 10 Oregon native plants for pollinators, based on Aaron Anderson’s 2017-2019 field trials of 23 Oregon native plants. We will feature one plant per week for 10 weeks, this is week 9! Profiles will include photos, planting information, and will highlight common pollinators of each plant.
Photo by Jen Hayes
Plant Facts
Scientific Name: Eschscholzia californica
Life Cycle: Annual/Perennial
Growth Habit: Clumping, sprawling
Bloom Duration: Early Spring to Late Summer depending on seeding date.
Hardiness Zone: 7-10
Special Traits: Drought-tolerant, deer and rabbit resistant.
When to plant: Seed in Fall for a Spring bloom, or seed in Spring for a mid-summer bloom.
Pollinator Facts
California poppy only provides pollen to its insect visitors, but provides it in an abundance!
Aaron’s study found California poppy to be associated with 4 species of sweat bees: Halictus farinosus, H. tripartitus, Lasioglossum dialictus sp. 5, L. olympiae, and a bumblebee: Bombus vosnesenskii.
Other common visitors to California poppy include butterflies, specifically, acmon blue and mormon metalmark.
Sweat bee leaving a California poppy. Photo by Jen Hayes
California poppy’s range extends from Washington to northwest Baja California and east towards Arizona and southwest New Mexico. A popular flower for roadside plantings, California poppy survives well in average to poor soil that is well-draining. It survives mild-winters as an herbaceous perennial and reseeds itself readily. California poppy is an all-around easy pollinator plant to grow, and growing it pays off, as it attracts an incredible diversity and abundance of bees with its remarkable volumes of pollen.
Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.
Did you know?
California poppy’s petals are responsive to light! In the absence of light (at night and on cloudy days) petals spiral around each other and tighten to a close. In the presence of light, cells in the petals expand in response to the plant growth hormone auxin. This mechanism opens the petals allowing pollinators to access the flower’s pollen — although in the field we watch impatient bumblebees force their way into closed California poppy flowers to get to the pollen anyways.
Petals close tight during the night and remain so on overcast days. Photo by iNaturalist user metacom CC some rights reserved
Poppies in various stages of opening and poppy buds enclosed in pinkish-green calyxes. Photo by iNaturalist user Daniel Das CC some rights reserved
Photos from the field
Sweat bee traversing stamen. Photo by Jen Hayes
The underside of a sweat bee with pollen on its abdomen and hind legs. Photo by Jen Hayes
Photo by iNaturalist user baileylemkau CC Some rights reserved.
Jen’s California poppy research plot. Photo by Jen Hayes
Tune in next week for the next edition of our Pollinator Plant PR Campaign.
