I have been so grateful for the opportunity to assist Jen Hayes with her nativar research project. For the past year and a half, I have learned so much in the world of plant and pollinator relationships. One of the most valuable things I have learned, which I use every day in my own garden, is how to quickly identify bees. In the field, we observe each flower plot for five minutes and record the different things that visit. Being able to identify a fly from a bee, or a bee from a wasp is very important in order to obtain accurate data. I wanted to share the process we use to quickly identify bees in the field and hopefully answer some questions you may have had about what was buzzing in your garden.
Once the sun has risen and the chill of the morning has left, bees begin their foraging routine. Male bumblebees, out foraging too late, emerge from the layers of Zinnia flowers. Hundreds of bees possibly pass through your garden in a single day, from flower to flower, collecting pollen and nectar. But what are they? Are they native? Are they helpful in the garden? These are all questions I have whenever I see something buzzing on the mint, exploring the flower patch, or pollinating the tomatoes.
The first things I always look for are the antennae and the number of wings. The flies that are most often confused with bees have short, almost non-existent antennae, whereas bees will have noticeable, segmented antennae. The wings are also something to look: flies only have one pair of wings and bees have two, the forewings and hindwings. Be sure to look closely! There are flies known as hoverflies or syrphid flies that have incredible mimicry adaptations. Look at these two insects on this butterfly bush. Although almost identical, you can see the top insect does not have noticeable antennae. That’s because it is a honey bee mimic!
If you have established that it is a bee and not a fly, there are other things to look for to identify the bee to a more specific taxonomic level. The coloration of the bee could help if it is green or red, but there are many bees that have different variations of black and white. What I like to look for next is the pollen baskets, also known as the corbiculae. Megachilidae bees carry the pollen on the underside of their abdomen, like bright yellow furry bellies. Another distinguishing factor for Megachilidae bees is how they fly. The abdomen of the bee will usually curl upwards while in flight. Mellisodes bees carry the pollen on their hind legs but the baskets are dramatically bigger than honeybees or bumbles. We like to think of them as pollen pants! Mellisodes bees are also known as long-horn bees because of their disproportionately long antennae.
If the bee does not have any special coloration or noticeably different corbiculae, it could be one of many other genera we have in Oregon. Halictidae bees range in size from the tip of a pen to the size of a penny. They are usually black or black and white and are VERY difficult to distinguish in the field. There are details we have to look for in the lab such as the number of “panels” in the wings or if they have one versus two sub-antennal sutures.
The other bees we see while doing research include wasps, honeybees, and bumblebees. There are so many variations of Bombus here in Oregon it is almost like a scavenger hunt. Because of all the color and striping variations, we use the PNW Bumblebee Atlas to help us identify species in the field.
Every June – August, from 2017-2019, we collected bees from 25 Portland area gardens. As I start to build out a Bee Guide for Portland Gardens, I wanted to highlight some of the notable bees that we collected. We are still waiting for our 2019 bees to be identified. The details, below, are for bees that were collected in 2017 and 2018 and identified by Sarah Kornbluth (2017) or Gabe Foote (2018).
We collected five species of bee in the genus Megachile:
rotundata (2 females and 1 male)
angelarum (8 females and 5 males)
perihirta (1 female)
fidelis (3 females)
centuncularis (1 female)
Worldwide, Megachile bees are extremely diverse: an estimated 1,400 species of Megachile bees can be found, globally and an estimated 140 species of Megachile can be found in the United States. These bees are in the Family Megachilidae, which includes the leafcutting (e.g. Megachile species), mason (e.g .Osmia species), and wool carder bees (e.g. Anthidium species). In the family Megachilidae, females carry pollen on their abdomen.
In this post, I wanted to cover Megachile fidelis, Megachile perihirta, and Megachile angelarum.
Generalist (Prefers Lavandula, Perovskia, Vitex)
Generalist (Prefers Asters)
Megachile angelarum was the most common bee in this genus that we collected from Portland area gardens.
Diet: Although this species has been collected from a broad array of floral hosts (see list from Discover Life), Frankie et al. (2014) note that this species prefers lavenders (Lavendula), Russian sage (Perovskia), and chaste tree (Vitex).
Sociality: This species is solitary, which means that each individual female builds her own nest, collects nectar and pollen to provision her young, and lays her own eggs. In bees with advanced social structures, such as honey bees, the workers collect nectar and pollen to feed the young, and the queen lays the eggs. Solitary bees die soon after they build their nest, load nest cells with pollen and nectar, lay their eggs, and seal the nest cell shut. Many solitary bees may nest in close proximity to each other. Thus, solitary bee doesn’t mean loner bee; it means that the female does all of the work on her own, without cooperation or collaboration from other bees in her species.
Nesting: Megachile angelarum nests in cavities. Rather than cutting leaves, females collect resins and gums to partition nest cells. Since this bee does not cut leaves, it lacks teeth on its mandibles, unlike other bees in the genus. The bee has been found in drilled pine wood (10cm deep holes, 0.5 cm in diameter; Dicks et al. 2010). Other studies have found this species in nest blocks with a 3/16th hole size (Galasetti 2017).
Appearance: Like many bees in this genus, it is a robust-sized bee, with females typically spanning 10-11 mm in length and males a bit smaller, at 8-9 mm in length. The lack of teeth and cutting edges on the mandibles can be helpful for identification.
Notes: Across 2017-2018, we collected this bee from seven different Portland area gardens, or nearly 1/3 of our sampled gardens. Megachile angelarum is likely parasitized by another bee, Stelis laticincta. Stelis laticincta is a social parasite, or cleptoparasite of other bees. What this means is that Stelis laticincta invades the nest of another bee, and lay their own eggs, just as cuckoo birds do with other birds. Once the Stelis laticincta eggs hatch, the larvae kill the Megachile angelarum larvae, and eat the pollen and nectar provisions that have been provided by the Megachile angelarum mother.
We collected a single Stelis laticincta in 2017-2018, and it came from a garden where we collected four Megachile angelarum specimens. Having a healthy Megachile angelarum population increases your chances of having more bee species, by supporting cleptoparasites, such as Stelis laticincta.
Megachile perihirta is commonly known as the Western leafcutter bee.
Diet: This bee is a generalist, and will collect nectar and pollen from many different types of flowering plants.
Sociality: Solitary (see notes for M. angelarum).
Nesting: Unlike many Megachile bees, this species does not nest in cavities, but instead digs shallow nests in the soil (Frankie et al. 2014, page 102). I had thought that all bees in the genus Megachile were cavity nesters. (Actually, I thought that all bees in the family Megachilidae were cavity nesters). But, Eickworth et al. (1981) report that soil excavation was widespread in the family Megachilidae and in the genus Megachile.
Appearance: This was the largest Megachile species we collected. Females typically spanning 13-14 mm in length and males span 12-13 mm in length.
I am soooooo sad that we didn’t collect a male of this species! The males have enlarged forelegs, covered with hairs (photos of the males can be found here and here), which the MALES USE TO COVER THE FEMALES EYES DURING MATING!!!! Biologists suggest that this helps to keep females calm and receptive, during mating (Frankie et al. 2014, page 103).
Notes: We only collected a single specimen of this bee. It came from our smallest garden (1,800 square feet in size), in an industrial area of Northeast Portland. And seriously: how cool is it to have a bee species where the mating ritual includes the male covering the females eyes with his super-hairy forearms!!!??
Diet: Frankie et al. (2014) note that this species seems to prefer plants in the Asteraceae, including Aster, Erigeron, Rudbekia, Cosmos, and Helenium). Hurd et al. (1980) note that this species is commonly collected from sunflowers (Helianthus).
Appearance: This species is another robust-sized bee. Females typically spanning 11-13 mm in length and males span 10-12 mm in length.
Once again, I am beyond bummed that we didn’t collect a male of this species! Males of this species also have enlarged forelegs covered with long hairs, although not as pronounced as in male M. perihirta. Once again, biologists suspect that the males use their hairy forearms to cover the females eyes during mating (Frankie et al. 2014, page 103).
Notes: We collected one specimen from a 0.2 acre, flower-filled garden that is adjacent to a golf course in Canby. The other two specimens were collected from a 0.1 acre, flower-filled garden in Northeast Portland.
Although I have been studying garden bees for the past three
years, I was never focused on honey bees. From a biodiversity point of view,
they are not very interesting to me. They are non-native and abundant. In fact,
honey bees were the most abundant bee species that we collected in
Portland-area gardens (332 individuals collected), even though we took great
care not to collect more than one individual per visit, when hand-collecting.
Honey bees, which hail from Europe, are only one of 20,000 bee species, worldwide. In North America, there are 4,000 species of bee. In Oregon, we have between 400-500 species of bee. From Portland area gardens, we have documented 86 species of bee (with our 2019 bees still awaiting identification).
Unlike some native bees, honey bees are not at risk of extinction. Compare this to bumblebees. We found 17 species of bumblebee in Portland gardens, two of which (12%) are at risk of endangerment or extinction, due to declining populations: Bombus fervidus and Bombus caliginosus. Across North America, more than 25% of bumblebee species are thought to be at risk of extinction.
By focusing ‘save the bee’ campaigns on honey bees, we may
be neglecting the bee species that really need our help. In fact, researchers
have started to call out organizations and advertising campaigns that promote
feel good stories about honey bee conservation as a form of ‘bee washing’. You
can visit www.bee-washing.com to learn
more about companies that promote their product or organization as being
bee-friendly, in a less than genuine way.
Researchers have documented at least seven different ways that honey bees may harm native bee species (summarized in Cane and Tepedino, 2016):
Honey bees monopolize and deplete nectar and pollen from local plant communities, which can reduce native bee reproduction.
By depleting local plant resources, native bee females have to devote more time and energy to fly and find new resources, which also reduces native bee reproduction.
Unlike honey bees, most bees are solitary, which means that they do not live in colonies and they do not have a queen. Solitary females who have access to fewer floral resources produce fewer daughters and more sons. Since female bees are needed to maintain a population, this skewed sex ratio can slow population growth and recovery in native bees.
When females collect less nectar and pollen, they have less food to feed their young. These bees grow up to be smaller, and are more likely to die over winter, compared to well-fed bees.
The longer a solitary bee mom is away from her nest, the higher risk that parasites and predators will attack her unguarded young.
Honey bees can physically block native, solitary bees from preferred pollen hosts.
Honey bees have many diseases. Some honey bee viruses have been found in native bee communities. Researchers think flowers that are visited by both native bees and honey bees are analogous to an elementary school water fountain: a place where repeat visitors can pick up a pathogen.
Please note that I am not suggesting that you extinguish honey bees from your garden. What I am asking, instead, is that you take the time to learn about and to notice some of the other 80+ species of bee that you might find in your garden. My group is creating a ‘Bees of Portland Gardens’ guide that we hope can help you in this journey. In the meantime, there are some great guides that are currently available. One is Wilson and Carrill’s ‘The Bees in Your Backyard: a guide to North America’s bees’. This book is available at Powell’s City of Books, as well as on Amazon. The second is August Jackson’s ‘The Bees of the Willamette Valley: a comprehensive guide to genera’. This free guide can be found online.
The first step to
saving something you love is to be able to recognize it and to call it by name.
Cane and Tepedino. 2016. Gauging the effect of
honey bee pollen collection on native bee communities. Conservation Letters10: