Meet the two-spotted longhorn bee, Melissodes bimaculatus. These summer bees are common garden visitors, so watch for them at your home or your local public garden. This bee’s name is due to the two white spots they have on the base of the abdomen (bimaculatus) and to the males’ long antennae (see photo). The genus name Melissodes means “bee-like.” Most Melissodes species are specialists, meaning they collect pollen from only one family or genera of plants. However, M. bimaculatus is a generalist bee that collects pollen and nectar from a wide variety of plants.
Taxonomy. Melissodes bimaculatus is in the family Apidae (same as honey bees and bumble bees) and the tribe Eucerini (longhorn bees). This species is one of nearly 100 species of Melissodes in the United States and one of 16 in Pennsylvania.
Where can you find it? This species can be found in most of the Eastern United States, although a few have been observed in the Rocky Mountain states. It is abundant in cities and farms.
Morphology and Life History. Melissodes bimaculatus is an all-black bee, with white hairs on its legs and two white spots on the base of its abdomen. Males are 11-13 mm long and have a yellow-white spot on their face above their mouthparts (clypeus; see photo). Females are 13-15 mm and have long white pollen-collecting hairs (scopae) on their hind legs that resemble loaded saddle bags when coated with pollen. Bees emerge from the ground in late June and remain active until mid-August. Even though these bees are solitary (meaning there is only one female in each nest), they can form large nest aggregations (see video). For nest construction, females prefer areas with loose soil on slopes and banks. Once nest-building activities begin, females collect nectar and pollen to provision each nest cell, lay an egg, seal the cell, and start building the next cell. Females spend each night in their nests, but males do not and can often be found sleeping on grasses and sticks in groups called “aggregations” (see photo).
Plant use. This bee species use nectar and pollen from a wide variety of plants including squash, morning glory, primrose, mountain mint, goldenrod, beebalm, zinnia, fragrant (anise) hyssop, and harebell.
Natural enemies. The larvae of M. bimaculatus are parasitized by cuckoo bees in the genus Triepeolus spp. These cuckoo bees lay eggs in the cells of M. bimaculatus nests and when the eggs hatch, the larvae of the cuckoo bee kill the host larvae and eat the pollen stored in the cell.
Holm, Heather, Pollinators of Native Plants, 2014
Tufts Pollinator Initiative, https://sites.tufts.edu/pollinators
Wilson, Joseph S. & Carril, Olivia Messinger, The Bees in Your Backyard, 2016