Nomia melanderi Cockerell 1906

The alkali bee (Nomia melanderi) is so named because it nests in moist alkaline soils, and is common in the western United States. The alkali bee is a member of the large and diverse Halictidae family of bees, which includes several genera and several hundred species worldwide. Some halictid species are commonly known as "sweat bees" because they are attracted to the salts in perspiration. Nearly the size of the honey bee, the alkali bee is black with iridescent green, yellow, or blue stripes on the abdomen of both sexes. Males are distinguishable from females by their larger antennae. All halictid bees are pollen feeders and may be important pollinators of both wild and cultivated plants. The alkali bee has become commercially important because it is an efficient pollinator of alfalfa. Halictid bees are generally not aggressive and only sting when swatted or startled.

The alkali bee is a solitary nester, in contrast to the highly social honey bee and bumble bee species, as well as some other halictid bees. However, alkali bees are gregarious in that individual females nest near one another, with as many as 50 - 100 nests per square foot. The nest is constructed by the female as a vertical tunnel 3 - 10 inches deep, with lateral tunnels terminating in cells. Males loiter near the nest sites, mating with multiple females as they construct the entrance tunnels. The female lines each of about 15 - 20 cells with soil and a waterproof oral secretion and provisions each cell with a 1.5- to 2-mm pollen ball composed of pollen and nectar. The female lays an egg on the pollen and seals the cell with soil. She completes approximately one cell per day. The eggs hatch within three to four days and the larvae consume the pollen balls within a week. Larvae overwinter in their cells, then pupate and emerge as adults in June or July, with males appearing a few days before females.

The alkali bee is native to the arid regions of the United States, west of the Rocky Mountains. They are managed to some extent in Nevada, Idaho, California, eastern Oregon, and Washington by alfalfa farmers who provide artificial nest sites. This species has also been imported to New Zealand, where it is managed for alfalfa production.

Halictid bees include some of the most common bee species in North America and on some other continents. The alkali bee, in particular, is among the more common native bees in the western United States. In some areas of the western U.S., managed alkali bee populations began to decline in the 1970s - possibly due to insecticide use on alfalfa or neighboring crops - causing some alfalfa farmers to turn to the non-native alfalfa leafcutter bee for pollination services.

For nesting habitat, the alkali bee requires moist alkaline soils with a salty (sodium or calcium) crust. Soils typically have a silt loam or fine sandy loam texture. Foraging female alkali bees cover a large area, straying up to five miles from the nest site, and visit a variety of flowers, including clovers, mint, onions, Russian thistle, salt cedar, and sweet clovers. However, alfalfa pollen and nectar within two miles of the nest site constitutes the primary food source for most females. Males visit flowers for nectar only. Female alkali bees tolerate a tripping mechanism unique to alfalfa flowers: the flower is held under tension; to gather pollen, the bee must trigger the release of the flower, and the bee's body is hit in the process. This tripping mechanism seems to discourage the honey bee from pollinating alfalfa, but does not deter the alkali bee.

The alkali bee (Nomia melanderi) has been managed for over 50 years as a pollinator of alfalfa (Medicago sativa) crops. It is a gregarious ground nester, with as many as 2,000 nests per square meter, and is the only intensively managed ground-nesting bee. Managers construct "bee beds," subirrigated silty nest sites with salt-crusted surfaces, for the bee. After the initial construction of these nest sites, minimal maintenance is required. The alkali bee is a better pollinator of alfalfa than European honey bees (Apis mellifera) because it works rapidly, stays in the crop, and trips the spring mechanism in the alfalfa flower that releases the pollen. In fact, a female bee's foraging activity results in about 1/3 pound of alfalfa seed being produced over its lifetime! This species is also an efficient pollinator of onion (Allium spp.).