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Nomia

Nomia – sweat bees & alkali bees (family Halictidae)
by Lisa Schonberg and Mace Vaughan (Xerces Society) and Gretchen LeBuhn (SFSU)

Genus summary: Nomia is a small genus of bees found in Eurasia, the Old World tropics and North America. There are 9 species in North and Central America and they are common in the western U.S. (Michener 1994). The most well-known Nomia species is Nomia melandri, the “alkali bee.” N.melandri is called “the alkali bee” because it nests in alkali soils. Alkali soils have a salty, dry surface and are moist underneath, and often appear whitish-grey. N.meandri lives in the Western United States and is an important pollinator of alfalfa. However, farmers have recently been using the introduced species Megachile rotundata, the “alfalfa leaf-cutter bee” instead (Michener 2000).

Floral relationships: Many Nomia are specialist foragers , and they have short tongues like the rest of the Halictids, which means that generally have an easier time accessing smaller or shallower flowers.

Nesting habits: Most Nomia make solitary nests in the ground. Some species nest communally, where two or more females share a nest but provision their own brood cells. In some species, new queens return to the same communal nests year after year, enlarging the nest with their cells. Nomia line their brood cells with a waxlike material they secrete as do other genera in the subfamily Halictinae (Michener 2000).

Diagnostic characteristics: Most Nomia have somewhat hairy dark bodies. Most species have hairless green, white, yellow, blue or opalescent (milky iridescent) bands on the abdomen; these bands are sometimes metallic (Delaplane & Mayer 2000, Michener 1994, 2000). They are moderate to large in size and between 0.3 to 0.6 inches long. Males have bizarre modifications on their hind legs; they appear swollen and are armed with spines. These spines are used to grasp the female during mating (O’Toole & Raw 1999).

Similar taxa:

Known conservation concerns:

Interesting fact: Alfalfa flowers have a unique way of ensuring that bees pick up their pollen. When a bee lands on an alfalfa flower, the flower’s pollen-bearing stamen strike the underside of the bee with some force, thus releasing the pollen in a small explosion. N.melandri and Megachile rotundata are efficient pollinators of alfalfa because they do not mind this explosive release. Honey bees, on the other hand, are inefficient pollinators of alfalfa because they learn to steal nectar through a slit in the flower and avoid being smacked by the stamens. Thus, they do not come in contact with alfalfa pollen (O’toole and Raw 1999).
Additional resources: Wcislo & Engel (1997)

Keys to Eastern Nomia at Discover Life

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