05/20/2026
Today is World Bee Day, and we wanted to celebrate by sharing a tale of two bee species and one special riparian plant. The lovely yellow-flowered plant pictured is known as fringed loosestrife (no close relation to the invasive purple loosestrife, by the way, which belongs to a whole different plant family!). This cheerful wildflower can be found around wetlands, streams, and in moist forests. It offers pollinators no nectar, but entices them with something else entirely: oil. Its floral oils are very desirable to pollinators, and one little bee absolutely depends on them for its survival: the oil-collecting Macropis bee (Macropis nuda). This little Macropis bee is a specialist, foraging exclusively for the floral oils this little wildflower produces, and it won't settle for anything else. That's interesting enough, but we promised you a tale of TWO bees, so here's the fascinating part: enter the Macropis cuckoo bee - a different species entirely, and one of the rarest bees in North America. This cuckoo bee (Epeoloides pilosulus) is federally listed as Endangered, and its lifestyle is so hyper-specific that it needs a highly intact, complex ecosystem for its survival. The cuckoo bee doesn't build a nest of its own. Instead, it is only able to lay its eggs in the nests of one other bee: our little oil-collecting Macropis! When the cuckoo bee's eggs hatch, the larvae consume food left by the oil-collecting parent, and this species relies on the oil-collectors as a host species that they cannot survive without. So for these little cuckoo bees to exist, there has to be a perfect set of conditions: patches of fringed loosestrife, which are being visited by a local population of oil-collecting bees, which are also nesting nearby for the cuckoo to find and lay its eggs in. A truly niche way of living, a specialist of a specialist. So on this year's World Bee Day, take a moment to stop and appreciate the beautiful complexity of our pollinators and the entire complex, interwoven ecosystems they depend on.
