Loosestrife Bees are among the rarest bees in the Northeast. They are unique in collecting oils from our native Loosestrifes (Genus Lysimachia) and are thus dependent on these yellow flowers. There is some evidence that these bees were once more common and widespread than they are today. Many hours of dedicated searching in 2019 and 2020 only turned up 5 individuals.

Female Macropis sp. © Spencer Hardy

As the name implies, Loosestrife Bees are not going to be found far from Loosestrife flowers, which are yellow-flowered forbs common around wetlands and in shrubby areas. Not all the Lysimachia species in Vermont are useful for these bees. So far all of the recent VT records have been off Fringed Loosestrife (L. ciliata), though Whorled Loosestrife (L. quadrifolia) and Swamp Candles (L. terrestris) may also be used. It is unclear if the non-native Lysimachia species are of any value to these bees – the often maligned Purple Loosestrife (Lythrum salicaria) is in a different family and ignored by Loosestrife Bees. Males occasionally visit other flowers in the area, particuarly Spreading Dogbane (Apocynum androsaemifolium).

Fringed Loosestrife (L. ciliata) © Spencer Hardy

Though its a small sample size, at least 3 of the 4 recent VT records are from large patches of native Loosestrife along moderate size meandering rivers with steep banks (where they are thought to nest).

The two Loosestrife Bee species that have so far been found in the state are our only representatives of the Family Melittidae, though several Blunt-horn Bees (Genus Melitta) are among our most wanted.

There is another, even rarer bee, that is an obligate kleptoparasite of Loosestrife bees and is so rare it was once thought to be globally extinct. It has since been re-found in several New England states. See Macropis Cuckoo Bee below.

Genus level ID

These bees are unlikely to be found away from blooming loosestrifes (June – August), however, most bees encountered on loosestrifes will not be Macropis. Look for a larger bee (slightly smaller than a honey bee) that is moderately hairy. Females look like they are wearing bell-bottoms, while males have yellow marks on their face.

Unless otherwise specified, photos are courtesy of Margarita Miklasevskaja at PCYU with funding from NSERC-CANPOLIN.

Species Accounts

A good key to the three New England species can be found here. Some, but probably not all, will be identifiable from photos. The hard part is finding the bees – take lots of photos if find one!

Dark-legged Yellow Loosestrife Bee (Macropis nuda) – Documented in the state prior to 1960, and subsequently found in at least 2020. A few recent records are not yet confirmed.

Macropis patellata – Documented in the state prior to 1960, recent records still need to be confirmed.

Macropis ciliata  Not yet found in the state, though the most common Macropis in Massachusetts.

Bonus bee

Macropis Cuckoo Bee (Epeoloides pilosula) – Listed as “Critically Imperiled” by Nature Serve. There are no known VT records, though it likely occurred here historically, and may still. Has been found several times recently in Massachusetts on Dogbane (Apocynum) in close association with Macropis and Loosestrife. A small, oddly proportioned, dark bee.

This map is displaying both Macropis records and records for the three species of Loosestrife (Genus Lysimachia) that the bees are likely to visit. Clearly the host plant is much more common than the bee!

Please note that many of our datasets have not been published yet, so the maps are incomplete.