Blog

Summer recap: a glimpse at pollinator fieldwork

The growing season is a busy time for pollinator scientists. Here’s what members of TPI got up to this summer! 

Cellophane bees

Nick, Leslie, and Lydia dug into the secret lives of solitary bees in New Hampshire. They want to know “where does a bee fly in her life?” To answer this, they caught and painted blueberry cellophane bees at nests to identify unique individuals. Then, they surveyed flowers and nesting areas to track daily movements. They painted over 1200 bees!

Bumble bees

Jessie, Lauren and Liana planted hundreds of goldenrod and sunflowers to find out how our growing practices affect the food available to bumble bees — an important native bee that pollinates tomatoes, peppers, melons and more. Bumble bees (like other bees) eat pollen and nectar, and need abundant, high-quality food to fly, pollinate, and raise new bees. They want to know how fertilizer and drought change plant growth, the number of flowers they produce, and the nutrient breakdown of their pollen and nectar. They spent the early summer digging, planting, weeding, and watering and ran a choice experiment to find out which plants bumble bees prefer to visit.

Baltimore checkerspots

Brendan spent the spring and summer studying the impact of the Junonia coenia Densovirus on Baltimore checkerspot population dynamics. He set up an enclosed experiment that exposes caterpillars to a gradient of viral loads and monitored the impact on their survival and reproduction. Later in the summer he continued field sampling for a project that is using a metagenomic approach to investigate whether Lepidopteran viruses are shared between co-occurring caterpillar species. This will help him understand the likelihood of disease spillover impacting species of conservation interest.

Honey bees

Isaac and Greta studied the effect that temperature stress has on the way honey bees arrange their comb stores. They hope to learn how increasing global temperatures will affect the structure of honey bee colonies.

Milkweed visitors

Atticus, Karen, and Kristina are looking at pollinator usage of milkweed in urban environments. Atticus and Karen observed monarch egg-laying behavior on milkweed, the monarch butterfly’s host plant, to see if it changes depending on surrounding landscape contexts, such as differing neighborhood flower garden densities. Kristina looked at milkweed flower visitors to see how visitation rates and species richness are affected by flower garden densities. You may have seen their pots at various park locations in Medford and Somerville!

Sweat bees

Chloé, Nick, and Aviel studied sweat bee (Agapostemon virescens) movement on Tufts’ campus. They want to know whether roads act as barriers to foraging bees. To answer this, they set up squares of four pots of coneflower bisected by roads at three sites on campus. At these sites, they caught and painted bees to identify unique individuals and recorded ongoing traffic.

Yellow-faced bumble bees

Across the country in California, Sylvie is studying the difference in life cycle patterns of Bombus vosnesenskii, the yellow faced bumble bee. Sylvie is interested in how life cycle timing of this bumble bee varies across its range. In the Sierras, B. vosnesenskii displays the characteristic timing of bumble bees – a queen emerges in spring, a colony grows over the summer with female workers, and at the end of the summer the queen stops producing workers and starts producing new queens and males. Then, the mated female queens overwinter underground! Sylvie is getting to discover firsthand the timing of Bombus vosnesenskii life cycle on the coast–and how it compares to timing in the mountains–since it has not yet been characterized! 

Pipevine swallowtails

James and Kaitlyn mated adult pipevine swallowtails and tested how growth rates in their offspring may be affected by differences in ambient temperature. These females laid eggs on Dutchman’s pipe and they collected those eggs to put in different thermal treatments. They will monitor those larvae until they’re ready to become adults themselves.

Monarch butterflies

Also in California, Emily studied monarch butterflies in urban gardens in the San Francisco Bay Area. Most people know monarchs for their impressive yearly migrations. Recently, however, year-round breeding ‘resident’ monarchs have also established in coastal cities in Northern California. These residents are associated with non-native milkweeds – namely Tropical Milkweed (Asclepias curassavica), which do not die off in the winter as the native species do and therefore provide breeding habitat throughout the year. We don’t yet know yet how resident and migratory monarchs interact with one another in urban gardens, and what the consequences of these interactions may be. In her research, Emily hopes to understand whether the resident monarchs in urban gardens are a population that is independent of the migratory one, or whether the presence of residents and their non-native host plants are contributing to overall monarch declines in the West.

Two-spotted longhorn bees love your vegetable garden

Two-spotted longhorn bees (Melissodes bimaculatus) love the city. This important crop pollinator is abundant in urban areas, and lucky for you, this highly distinctive bee is easy to identify. Read on to learn how to spot one in your garden (hint: look on squash and corn) and check out our field ID guide or this species profile on watchingbees.com for ID tips.

Range

Melissodes bimaculatus can be found across eastern North America, from Texas to Florida, but also as far west as the front range of Colorado. Populations occur to Minnesota and Maine.

Active Period

Two-spotted longhorn bees are active for about six weeks of the growing season—in Massachusetts, from late-June through early August—and produce one generation per year.

Appearance

Two-spotted longhorn bees are about 0.75-1x the size of a honey bee. Males are jet black, with long curly antennae, a cream-colored patch on their face, and thin white hind legs.

Female M. bimaculatus are larger and stockier than males, but with shorter antennae. They have thick brushes of white hairs on their hind legs for carrying pollen (though these hairs can be obscured by orange or yellow pollen). They also have two namesake white spots on the sides of their abdomen, though these spots are often hard to see. Females have have all black faces.

One lookalike to watch out for is the carpenter-mimic leaf-cutter bee (Megachile xylocopoides). This species is found only as far north as southern New Jersey. Females of this species carry pollen beneath their abdomens, not on their legs, and both sexes often hold their wings out at a 45˚ angle while foraging.

Male Behavior

In late-June, males emerge from the ground and patrol patches of flowers in search of females. Male M. bimaculatus are zippy; they speed through the garden, only stopping briefly to sip nectar or rest on a leaf. At night, males sleep on vegetation. They bite twigs or long blades of grass, often two to three feet off the ground, and hang on all night long with their mandibles. Males are highly faithful to particular sleeping perches, and will often sleep near other males. Maybe your garden is home to one of their adorable slumber parties!

Female Behavior

Females emerge shortly after males and get to work collecting pollen and nectar provisions for their solitary underground nests. Despite their abundance, two-spotted longhorn bees nest in obscurity; few nests have ever been documented. We suspect they nest in sparsely vegetated soils, such as those found on the margin of a garden bed. If you think you’ve found a nest, please reach out!

Floral preferences

The best way to spot M. bimaculatus is to spend time watching your garden in mid summer. Male and females drink nectar from a variety of common vegetable garden plants, including cucumbers, squash, black-eyed susans, oregano, cosmos, purple coneflowers, and zinnias. Females specially like visiting tubular flowers such as wild bergamot (Monarda fistulosa), hoary vervain (Verbena stricta), and mountain mint (Pycnanthemum).

Females collect pollen from a staggering array of plants, including asters like black-eyed susans (Rudbeckia) and cosmos, pumpkins and zucchini (Cucurbita pepo), moss rose (Portulaca grandiflora), rose of sharon (Hibiscus syriaca), and morning glories (Ipomaea purpurea).

 In addition, while studying M. bimaculatus movement in urban gardens last year, TPI scientists noticed that this species has a curiously strong affinity for corn pollen (Zea mays). This was unexpected since corn flowers have evolved to disperse pollen on the wind, not via insects*. Corn pollen is dry and light, and the flowers produce no nectar, so we figured that M. bimaculatus must have been seeking out corn flowers for pollen. Upon a closer look, we saw a female actively packing corn pollen into her scopae, i.e. the thick hairs on her hind legs. We followed up on our observations by visiting local farms in the area growing corn. Sure enough, M. bimaculatus was on corn flowers in every single field.

This remarkable association between M. bimaculatus and corn raises many more questions than it answers. Corn is not native to eastern North America—though it has been grown here for thousands of years by native peoples—so which came first? Did M. bimaculatus arrive in this region following widespread trade of corn? Or did M. bimaculatus evolve a local preference for corn pollen since few other flower-visiting insects use this resource? Regardless, we encourage you to look for M. bimaculatus on corn flowers in your garden this year.

Share your findings on iNaturalist or comment on this post! Happy bee watching.

*By collecting pollen from tall male corn flowers, M. bimaculatus is a pollen thief, not a pollinator. M. bimaculatus is not a corn pollinator since it never visits the female flowers of corn plant (the silky ears lower down on the plant), which produce no pollen and offer no nectar.

How to stop bunnies from eating your pollinator garden

Don’t be fooled by extreme cuteness: bunnies are every pollinator gardener’s nightmare. You spend precious time and money planting a native garden to feed pollinators, only to end up feeding bunnies instead. In the TPI gardens at Tufts, we face our fair share of bunny herbivory. But, we’ve also learned a few strategies for combating hungry rabbits, including a list of which plants rabbits avoid entirely. Read on to learn our tips for how to bunny-proof your pollinator garden, and visit our native plant sale in mid-June to pick up plants that will thwart the rabbits!

1. Prioritize rabbit-proof plants

The single best way to avoid having your garden munched on by rabbits is to grow plants that rabbits do not like to eat. Over the past three years, we have kept track of the fates of over 30 different species of native plants in our gardens. Although many of them, in one year or another, have been munched on by rabbits, some species have been avoided entirely. Here is the list of plants from our garden that have never been eaten by rabbits:

  • Mountain mint (Pycnanthemum spp., e.g. P. virginianum, P. tenuifolium)
  • Anise hyssop (Agastache foeniculum)
  • Bee balm (Monarda spp., e.g. M. bergamot, M. punctata)
  • New York ironweed (Vernonia noveboracensis)
  • Foxglove beardtongue (Penstemon digitalis)
  • Golden Alexander’s (Zizia aurea)
  • Goldenrods (Solidago spp. e.g. S. sempervirens)
  • Wild senna (Senna hebecarpa)
  • Joe-pye weed (Eutrochium maculatum)
  • Boneset (Eupatorium perfoliatum)
  • Cutleaf coneflower (Rudbeckia laciniata)
  • Sneezeweed (Helenium autumnale)
  • Partridge pea (Chamaecrista fasciculata)
  • (most herbs*)

2. Avoid tasty plants

In a similar vein, a great way to make your garden bunny-proof is to not grow the plants that rabbits love. Here’s a list of plants from our gardens that fed more rabbits than pollinators, and which should be planted with caution:

  • Symphyotrichum spp.asters (S. novae-angliae, S. laeve, S. prenanthoides)
  • Blazing star (Liatris spicata, L. scariosa)
  • Wild false indigo (Baptisia spp.)
  • Cardinal flower (Lobelia cardinalis)
  • Swamp milkweed (Asclepias incarnata)
  • Purple coneflower (Echinacea purpurea)
  • Cup-plant (Silphium perfoliatum)
  • Black-eyed susan (Rudbeckia hirta)
  • Sunflowers (Helianthus spp.)
  • red columbine (Aquilegia canadense)
  • Culver’s root (Veronicastrum virginicum) — not always eaten

3. Create an unappetizing display by mixing plants

We’ve found that tasty plants are often avoided when planted among distasteful plants, so try to mix and match. This means your tasty asters stand more of a chance if mixed in with lots of distasteful mountain mints, ironweed, and goldenrods. Pollinators appreciate the diversity too—the more diverse your garden, the more kinds of pollinators you will attract! And, from an aesthetic perspective, inter-mixing plants means that any rabbit herbivory that does occur will be far less noticeable.

4. Protect vulnerable plants

Rabbits love eating the youngest plants. Often, young leaves have not yet accumulated as many distasteful chemical compounds as older leaves. In our gardens, for example, young emergent sunflowers (Helianthus annuus) and cup-plant (Silphium perfoliatum) are frequently nibbled as seedlings, but are left untouched when they are larger. By protecting young plants with fencing, your garden will have the blooms you want later in the season!

The same applies to woody plants and saplings, but for a different reason. Young wood is soft, sweet, and easily chewed by rabbits and rodents. Be sure to fence young saplings in their first years–especially over winter–to prevent girdling and other herbivory that can kill your long-term investment.

5. Use your local knowledge

Keep in mind that our lists of plants (both enjoyed and rejected) reflect the tastes and preferences of rabbits in urban Massachusetts, as well as the context of our campus garden. So, to make your garden as bunny-proof as possible, learn from experience. If bunnies in your neighborhood never touch the wood asters and swamp milkweed in your garden, then by all means, plant, plant, plant. Conversely, if the bunnies in your neighborhood have a penchant for anise hyssop, then definitely don’t keep planting while expecting a different result.

Do you have tips for thwarting bunnies in your pollinator gardens? Drop us a comment!

*Although we advocate for growing native, you can add fragrant, non-native herbs like lavender, rosemary, thyme, borage, and oregano to make your garden even more bunny-proof. The nasty compounds in most mint-family plants are quite distasteful to bunnies.