With over 850 species, the genus Nomada is one of the largest genera in the family Apidae, and the largest genus of cuckoo bees. Cuckoo bees are so named because they enter the nests of a host and lay eggs there, stealing resources that the host has already collected. The name "Nomada" is derived from the Greek word nomas (νομάς), meaning "roaming" or "wandering."
Nomada are kleptoparasites of many different types of bees as hosts, primarily the genus Andrena, but also Agapostemon, Melitta, Eucera and Exomalopsis. As parasites, they lack a pollen-carrying scopa, and are mostly hairless, as they do not collect pollen to feed their offspring. Like non-parasitic bees, adults are known to visit flowers and feed on nectar. Given the lack of scopa and general behavior, they are considered poor pollinators.
Appearance and identification
They are often extraordinarily wasp-like in appearance, with red, black, and yellow colors prevailing, and with smoky (infuscated) wings or wing tips. They vary greatly in appearance between species, and can be stripeless, or have yellow or white integumental markings on their abdomen. There are specialized patches of hair on the tip of the abdomen of female Nomada. Males have an obvious, often notched pygidial plate. In general, females are easily identifiable by the lack of scopa, reduced body hair, thick exoskeleton, and mandibles.
Separation of this genus from other Nomadinae can be difficult; details of the wing venation, and the nature of the patch of silvery setae at the tip of the female metasoma are the best distinguishing features.
Species of Nomada exhibit an unusual behavior where adult bees are observed to be sleeping by using only their mandibles to hold onto plants.
Distribution
Nomada occur worldwide. All known species parasitize ground-nesting bees, and their habitats and seasonality correlate with their hosts. Ground nesting bees nest in soil, either in open habitats or in ones covered with vegetation, with a good floral source...
