Coelioxys / cuckoo Bee
Male Coelioxys rufitarsis. © Rollin Coville
Female Coelioxys sayi (Say's Cuckoo Leaf-Cutter) on chrysanthemum in Temple Hills, MD. © Barbara Thurlow
Coelioxys on Helenium. © Celeste Ets-Hokin
Common Name: Cuckoo Bee
Mostly hairless, slender bees with a thick cuticle to withstand attack from their hosts; they have dark abdomens which are highly tapered, ending in a point, with distinctive thin white banding.
Since the female does not forage or provision nests for her offspring, she lacks the specialized hairs on either her hind legs or abdomen to carry pollen.
One of the most common genera of kleptoparasites in North America, and can often be seen in garden settings. The females are frequently found visiting many of the same flowers for nectar as the host species, which belong to the genus, Megachile.
Cuckoo bees detect the nests of their host bees by their particular scent. Once the host nest is detected, the female cuckoo bee will loiter near the nest entrance, waiting for the host female to leave on a foraging trip – when the host female has vacated the nest, the female cuckoo bee slips into the nest and lays her own eggs.
The developing larvae of cuckoo bees have specially shaped jaws which are used to destroy the host egg or larvae, thus commandeering all the food provisions for their own nourishment.
Approximately 20 percent of North American native bee species are cuckoo bees.
Size: Small to moderate, slender bees, 1/4 to 3/4 inch in length
A widespread genus, with species on most continents. Coelioxys are widely distributed across North America, with numerous species in the U.S. and Canada.
Number of species in North America
Approximately forty species north of Mexico
Spring to summer, depending on species
Coelioxys species are kleptoparasites, that is they lay their eggs in the nests of other bees that have already been provisioned with food stores by the host.
Females of Coelioxys lay their eggs in the nests of Megachile species, which they detect by scent.