Wild Side: Bee season is here

First find is a species that particularly enjoys blueberry blossoms.


My first native bee of the season? Why, thank you for asking! It was a male Bradley’s mining bee, Andrena bradleyi, which I found on April 4 along Lambert’s Cove Road. And it was a fine way to start the season: This species is an unusual one, with odd ecological associations and striking physical features.

I presume the species was named in honor of James Chester Bradley (1884-1975), a famous entomologist (to the extent that such a thing exists) who specialized in hymenoptera (bees, wasps, and ants). The species ranges from Florida north to Nova Scotia, and west through the Appalachians and Great Lakes. One source shows an odd, isolated set of records along the “front range” of the Rocky Mountains; I have to wonder if these don’t reflect confusion of bradleyi with a very closely related Western species, Andrena cheyennorum.

The greatest concentration of bradleyi records is in eastern Massachusetts, including the Cape and the Vineyard (I can find no records from Nantucket, though I bet this species occurs there). The Pine Barrens of New Jersey also account for a lot of bradleyi records, and this pattern points to a strong habitat preference: Bradley’s mining bee likes sandy, acidic soils dominated by oak and pine.

It isn’t the oak and pine that attract this bee, however. Overall, this is a bee that associates strongly with blueberry, with female bradleyi even showing long mandible and an elongated face to facilitate feeding on the deep blossoms of blueberries.

But the use of blueberries is hardly a firm orthodoxy for this bee. The Vermont Atlas of Life notes that while A. bradleyi can be fairly common on blueberry farms in that state, it is infrequently observed on wild blueberries. An even odder situation applies on the Vineyard: As far as I can tell, adults of this species have finished their reproductive work and disappeared before blueberries have come into flower.

Instead, I’ve found male bradleyi on willow blossoms, which are among the very first floral resources to become available in spring. Both males and females turn up on the pink or white, exquisitely scented blossoms of trailing arbutus, which is in the same family as blueberry, and features deep, almost tubular flowers. And this spring I found a male bradleyi on Pieris japanica, an exotic shrub used as an ornamental; it’s also in the blueberry family, and has blossoms resembling those of its native relative.

Andrena bradleyi is an early-season bee. Over its large geographic range, records span from February into June. But there is a strong peak in abundance in April, and all my records from the Vineyard fall in the first half of the fourth month. It seems to occur fairly widely on the Vineyard: I have records from throughout Correllus State Forest, and from several locations along Lambert’s Cove Road. I expect it occurs elsewhere in places I haven’t yet looked.

As the genus Andrena goes, bradleyi is a pretty recognizable species. Its early flight period helps: While bradleyi overlaps with a number of other Andrenas that occur here, it is reliably one of the first to appear, and one of very few bee species in any genus that can be found at the beginning of April.

But this bee’s appearance is distinctive, too. Males, which are about a centimeter long, have a yellowish-white patch on the clypeus, which is the plate that covers the lower portion of a bee’s face. The patch is variable in size, and to some extent in color, but it never covers the whole clypeus and always appears (if seen well enough) to be completely surrounded by black. No other local Andrena has anything like it.

Female bradleyi run a bit larger, up to about 12 millimeters in length. As is usual with bees, females are much hairier than males, an adaptation that helps them carry pollen back to their underground nests. And they lack the male’s pale patch on the clypeus. But the elongated, blueberry-friendly face I mention above is often a workable field mark.

Moreover, female Andrenas of any species have grooves along the sides of their faces, along the inside margin of the eyes. Called “facial foveae,” these grooves vary in length, depth, shape, and even the color of the fine hairs that line them; the characteristics of the foveae are a crucial tool for identifying female Andrenas. In the case of bradleyi, these grooves are long, very narrow, and boldly lined with white hairs, so they stand out dramatically against the otherwise black face.

Andrena bradleyi is only one of about 185 bee species known from Martha’s Vineyard. But it’s fair to call it a local specialty. And for the lover of native bees, its early season makes it a welcome site: The first bradleyi signals that bee season has begun.