ARTICLE BY: SUSAN MASTA

Susan Masta is a biology professor at Portland State University, and also curates the insect collection at PSU’s Natural History Museum. Her garden is very much a part of her teaching, as she integrates her observations in her garden into her courses and public outreach efforts.

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It’s 6 pm and still a sweltering 97 degrees F outside. Time to get out of the house shuttered against the heat and take a stroll through the shaded part of the garden. Stepping outside I can see the catmint, Nepeta ‘Walkers Low,’ is abuzz with Vosnesensky bumble bees. These bumblebees seem to be much more tolerant of the heat than the Fuzzy-horned and Yellow-fronted bumblebees I saw nectaring on the Abelia grandiflora flowers at 6 am today, when the temperature was much cooler. Looking closely, I can see that the flowering oregano, intermixed with the Nepeta, is also dripping with bees, albeit much tinier, such that several bees could easily perch on top of my little finger.

Bombus vosenenskii on Nepeta

Gardening has always been a passion for me, as it has filled me with happiness to watch a plant grow, to observe how the garden changes with the seasons, and to learn to look closely at nature. Just as I wait in anticipation for the glow of yellow from witch hazels blooming in the winter and the first smell of lilacs in the spring, I treasure watching the arrival of the different types of pollinating insects throughout the year. Even on unbearably hot days in July, there is an amazing diversity of bees active in the garden. Let’s continue the stroll through the garden while I introduce you to some of the summer bees that are active this evening.

I use a magnifying lens to see some of the details on the bees on the oregano. Looking at how the beige bands on the segments of the abdomen are arranged tells me that there are two different species of bees foraging right next to each other, in the genera Halictus and Lasioglossum. Both of these belong to the bee family Halictidae, and both nest in the ground. This year we got rid of the last little patch of lawn left in the yard to convert it to a meadow for ground-nesting bees such as these. These solitary bees need hard ground in which to burrow and create a nest for the eggs they will lay underground, each egg provisioned with pollen for the growing bee to eat as it develops. A single female bee may tunnel into the ground as far as several feet deep to create nesting chambers. It has been amazing to watch these tiny bees as they manage to dig through the compacted clay that I have been unable to work without the use of heavy tools.

Bombus vosnesenskii on Eschscholzia californica

Watching the meadow grow and the bees nesting has been an endless source of entertainment this year. In the winter we’d hired Randy Raburn to excavate a pond and patio on one side of the front yard and remove the meager lawn until bare clay was exposed on the other side. This patio has proven to be a magical place to watch the garden, pond, and bee activity over the season. We planted spring annuals in the clay, anchoring the meadow with a few kinds of perennial bunchgrasses. The spring annuals in the meadow have come and gone, and now the California poppies dominate. These poppies are full of Vosnesensky bumble bees from the time they open in the morning until they close in the evening. The bees circles round and round in the center of the flowers, grabbing as much pollen as they can load onto the specialized pollen baskets on their hind legs. They will carry the pollen back to the nest to provision the eggs that the queen bumble bees have laid. Now, as the sun drops in the sky and the meadow becomes shaded and the poppies are closing, I watch as the bumble bees frantically try to pry open the closing blooms to get one last load of pollen before they return to their nest for the night.

Melissodes female on Rudbeckia fulgida

The garden nearest the street in still lit by the evening sun, and the black-eyed Susan flowers are dancing with long-horned bees, in the genus Melissodes. These long-horned bees are one of my favorite summer bees. These are bees with style and attitude; males have oversized long antennae, and females have enormous pollen collecting hairs on their hind legs that remind me of costumed flamenco dancers. Depending on the flowers they have been foraging on, their leggings vary from yellow to orange. To provision their underground nests, the Melissodes common in my yard appear to rely primarily on pollen from flowers in the sunflower family, and tonight the girls are all sporting golden leggings from the pollen of Rudbeckia and Inula planted in our drought-tolerant streetside garden.

Megachilidae female on Rudbeckia fulgida

The nearby threadleaf Coreopsis ‘Zagreb’ is currently entertaining bees in the family Megachilidae, easily seen by noting that the underside of the female’s abdomen is coated in yellow Coreopsis pollen. Female megachilid bees have long belly hairs that pick up pollen as they walk across the surface of a flower, and I typically see them on composite flowers. Unlike the other bees I have seen tonight that nest underground, many megachilid bees (also called leaf-cutter or mason bees) nest in holes in wood. If our yard were not located in such an urban environment, there would be many trees around with dead branches, or entire dead snags, riddled with holes created by wood-boring beetles. Once the beetles have emerged and left the empty holes, these holes would typically be populated by such bees. We had to remove some large branches from trees in the past few years and we cut these into short sections and drilled holes of various sizes in them in order to provide nesting habitat for a diversity of bees. We scattered these pieces of wood around the yard, and I note that the ones around the meadow area have recently been filled by leaf-cutter bees. They line the insides of their nest holes with leaves, or sometime flower petals, that they cut with their sharp mandibles. Their relatives the mason bees usually plug their nest holes with mud, so I can readily tell which of these types of bees have been filling up our nesting blocks.

As the evening progresses, the bees will go to sleep for the night. Already there are some bumble bees asleep on the rose bushes. Many female bees with nests will return to their nest for the night, while male bees never enter nests, but instead sleep clinging to plants. The evening air is finally starting to cool down, and it’s time to enjoy a glass of chilled white wine on the pond-side patio while the garden activity winds down for the night. … We relax, and I wonder: What bees will August bring?

Bombus flavifrons female