Native bees

We have at least 182 species of bees on the Island.

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The sweat bee Agapostemon virescens, a common and colorful Vineyard bee. —Matt Pelikan

Pollinators, we all know by now, are both important and in trouble. Many populations within this broad guild of insects are shrinking, precipitously in some case, and everyone from farmers to ecologists is worried about what will become of the plants that depend on pollinators for successful reproduction.

Bees, in particular, are a focus of concern, largely because their anatomy and feeding habits make them pollinators par excellence. Many native bee species have very specific ecological requirements, making them vulnerable to ecological deterioration. And the usual culprits — habitat conversion and fragmentation, climate change, pollution, invasive pests, and pathogens — appear to be driving bee numbers and diversity generally downward.

Meanwhile, an apparent population decline in one particular bee species, the honeybee, has alarmed agriculturalists across the continent. Much of modern agriculture depends on the labor of honeybees; indeed, a robust industry exists keeping honeybees and transporting them to crops in need of pollination. But both domesticated and feral honeybee populations have been decimated by a mysterious syndrome referred to as colony collapse disorder.

From the perspective of this column, the attention showered on honeybees is a little bit misplaced. While humans have chosen to develop agricultural methods that rely on honeybees, this insect is a non-native species in North America. And while it pollinates some crop species (notably fruit and nut trees) with commendable efficiency, it’s not a particularly effective pollinator for many native plants (or even for some common crops). And there is a small but steadily growing body of research suggesting that introduced honeybee populations, armed with highly evolved social habits, can outcompete and suppress the native bees that actually do a better job pollinating native plants.

Happily, some elements within the very large world of agriculture recognize the value our native bees can bring, not just to native systems, but to agriculture as well. After all, there are many hundreds of native bees, and such diversity means it’s highly likely that whatever your pollination needs, there is a native bee species around that can help you out.

The honeybee is probably here to stay, as a feral species as well as a commercially managed one. But more and more farmers and gardeners are making provisions to support their local native bee diversity and populations: Leaving patches of bare soil for the many bees that nest underground; leaving edges of crop fields unmanaged, so a diverse plant life can attract and support a diverse bee fauna; minimizing pesticide use; even creating wooden structures for bees that like to nest in hollow stems or tunnels bored into wood.

I’m hardly an expert on native bees; bee identification routinely flummoxes me, and I know little about the ecology of specific bee species. But I know enough to be impressed by the Vineyard’s native bee fauna: Bumblebees, sweat bees, mining bees, carpenter bees, leafcutter bees, even so-called “cuckoo bees” that are parasites on other bees. In all, at least 182 species of bees inhabit the Island, according to an exemplary survey coordinated by entomologist Paul Goldstein in 2010–11.

With such a high diversity of bees, it’s not surprising to find a diversity of life histories as well. Bees of one kind or another are active almost year-round on the Vineyard, among the first insects active in spring and the last to disappear in the fall. With their hairy bodies and penchant for visiting flowers, these insects amount to a comprehensive pollination service for native plants (and crops as well, if conditions allow).

In contrast to the highly social honeybee, many of our native bees are so-called solitary species. Each individual female bee has her own nest, built in whatever manner her species has evolved. Stocking the nest with pollen, she lays one or more eggs in it, and the larval bees feed on the stored pollen between when they hatch and when they emerge as adults.

If you’re interested in the roles native bees play in agriculture and the ecosystem, you’ll want to attend a lecture this coming Tuesday, May 9, at 7:00 pm in the Martha’s Vineyard Agricultural Society Hall. Sponsored by the Dukes County Conservation District, Polly Hill Arboretum, Island Grown Initiative, and the Martha’s Vineyard Agricultural Society, this presentation brings Linda Rinta to the Island to discuss bee conservation and the pollinating power of native bees.

It sounds like the focus of the talk will be largely on bumblebees (a small group, if an important one), and on pollination of crops more than pollination in natural environments. Still, this columnist plans to be there, relieved to see attention paid to some of our native bees instead of a foreign interloper. Encouraging native bees represents a rare win-win, in which the needs of both humans and wildlife can be met simultaneously.