Photo of a Nomada male by Hartmut Wisch
Nomada – cuckoo bees (family Apidae)
By Lisa Schonberg and Mace Vaughan (Xerces Society) and Gretchen LeBuhn (SFSU)
Genus summary: The genus Nomada occurs worldwide and contains 795 species (O’Toole & Raw 1999). There are approximately 287 species in the U.S. and Canada (Michener 1994), about 90 in the northwestern portions of the U.S. and Canada (Stephen et al. 1969), and about 54 are known from New York State (Danforth & Magnacca 2002). They can be found as far north as Alaska, and are common in temperate areas but rare in the tropics.
Nesting habits: All species in the genus Nomada are clepto-parasites on other genera of bees. Clepto-parasitic bees are commonly referred to as “cuckoo bees.” Clepto-parasites do not collect pollen or provide for their own young; they instead deposit their eggs in the nests of other bees. When their larva hatch, they eat the host bee’s young and provisions. Nomada are primarily parasites on Andrena bees, but also attack Agapostemon, Halictus, and Lasioglossum. Nomada typically lays two to four eggs alongside the one Andrena egg typically found in each Andrena nest. The first Nomada larva to emerge eats its siblings, the Andrena egg, and then all the provisions in the cell (Michener 2000). In the first larval stage (instar), Nomada have large sickle-shaped mouthparts as larvae that enable them to kill their host’s young (O’Toole & Raw 1999).
Diagnostic characteristics: Nomada are minute to small bees 0.1 to 0.6 inches long (Michener 2000). They are slender, sparsely haired, and wasp-like. Most species are black or red, and the majority of species have yellow or white markings (Michener 1994). Nomada lack pollen-collecting hairs because they do not visit flowers for pollen, but instead steal it from other bees.
Similar taxa: Nomada may easily be mistaken for small sphecoid wasps, but there are a couple of distinguishing characters. Sphecoid wasps have silvery or gold hairs on the lower part of their face that make it look like their face is glittering in the light, whereas Nomada do not. In addition, if you use a microscope, Nomada, like all bees, have branched (plumose=feathery) hairs while wasps have unbranched hairs (Michener 2000).
Known conservation concerns:
Interesting fact: The male Nomada bee mimics the odor of Andrena females. He patrols the Andrena nest site emitting this mimic odor in order to help attract Nomada females and make it easier for her to find an Andrena nest, as well as a mate (O’Toole & Raw 1999).
Additional resources: Nomada hosts: Snelling (1986).