Bees

BEES: ANTHOPHILA

Bees belong to the Phylum Arthropoda, the Class Hexapoda, and the order Hymenoptera, which also includes ants and wasps. They are monophyletic and form a clade called Anthophila. About 20,000 bee species have been described to science, with about 380 species in Massachusetts (Mass. Dept. of Agricultural Resources, 2016). There are seven bee families, six of which are represented on Martha’s Vineyard. The seventh, Stenotritidae, only occurs in Australia (U. of Minnesota Bee Lab, 2015).

The first bees evolved from wasps about 130 million years ago, transitioning from a predatory lifestyle to a pollen-based diet (Goulson 2014). Since then, bees have adapted to better feed on flowers in a number of ways. On the females of most species, hairs on the legs or abdomen collect pollen from flowers, and in bumblebees and honey bees bristles on the legs also form pockets, called corbiculae, specifically for pollen collection. In other species, pollen may be carried on hairs under the abdomen, as in the genus Megachile, or even internally, as in the genus Hylaeus. Some bees provision their nests with oil, rather than pollen, as in the genus Macropis. Still other bees don’t bother collecting anything at all: a significant portion of bee species are nest parasites or “cuckoo bees,” laying their eggs in the nests of other species. The parasitic genera Sphecodes (Halictidae) and Nomada (Apidae) are both well represented on Martha’s Vineyard. In addition to pollen, nectar from flowers is an important resource for bees, offering an easy source of flight-sustaining sugar.

About 80 million years ago, some bees evolved a social lifestyle (Goulson 2014), evolving into the most commonly known cases of eusociality, colonial existence involving cooperative care of juveniles and a division in reproductive responsibility (Wilson & Hölldobler 2005). Many of the most widely known bees, including honeybees and bumblebees, exhibit eusociality.

In addition to the well-known honey bee, Apis mellifera, we know of a few other exotic bees on the island. One of these is the Giant Resin Bee (Megachile sculpteralis), which was first documented in Chilmark in September 2003 (Keith, 2003). It is a species originally native to eastern Asia that was first found in the United States in 1994 and in Massachusetts in 2002. Apparently the result of accidental introduction, Osmia taurus and Osmia cornifrons are now quite widely distributed across the eastern United States. Megachile rotundata has been found in Correllus State Forest. Since we do not yet have a wasp section, it is worth mentioning here that at least two potentially invasive vespid wasps, Polistes dominula and Vespula germanica, have also colonized Martha’s Vineyard.

The data for this section derives mostly from a magisterial 2010-2011 study of Martha’s Vineyard bees coordinated by Paul Goldstein and John Ascher, with results published in 2016 (Goldstein and Ascher 2016). The authors and their many volunteer collaborators surveyed more than 60 sites on the island and collected more than 14,500 specimens, documenting 182 species for the island. Goldstein and Ascher also documented four Vineyard species identified from museum collections, included in our checklist, bringing the number of documented Vineyard species to 186.

Since the appearance of that publication, 15 additional species – Andrena bisalicis, A. ilicis, A. kalmiae, A. alleghaniensis, A. cornelli, Protandrena compositarum, Sphecodes brachycephalus, Perdita bradleyi, Coelioxys modesta, C. octodentatus, Megachile rotundata, M. inimica, Osmia taurus, O. cornifrons, and Melissodes subillatus – have been documented on Martha’s Vineyard by some combination of “Research Grade” observations in iNaturalist and specimens in the BiodiversityWorks collection. An Epeolus specimen in that collection is not any of the Epeolus species listed in Goldstein and Ascher (2016). It most closely resembles E. inornatus, described only in 2018, and may either be that species or perhaps a closely related species that has not yet been described. It is listed here as Epeoleus nr. inornatus. This brings the tally of bees known from Martha’s Vineyard to 201, validating Goldstein and Ascher’s (2016) estimate that the true number of species on the island likely exceeds 200. Several puzzling specimens in the BiodiversityWorks collection have not yet been identified and may represent additional species once they receive expert attention. Moreover, new arrivals are always possible in addition to whatever species are currently present but overlooked. So substantial work remains to be done in exploring the Vineyard’s bee fauna. Finally, we should note that the Halictid bee that Goldstein and Ascher (2016) included as Augochloropsis metallica has been re-named A. viridula here, following a 2022 taxonomic change.

Goldstein and Ascher (2016) found that 74% of the island’s bees are soil-nesters, and half are solitary, both comparable with Massachusetts-wide numbers. The nine most abundant species found in the survey were eusocial halictine sweat bees. They also found species with no or few recent records elsewhere in the Northeast, such as Anthophora walshii, whose presence on Martha’s Vineyard may represent remnant populations sheltered on the island from mainland threats.

Andrea Brown; edited by Matt Pelikan, July 2, 2024