golden sweat bee

Golden sweat bee is a common, ground nesting, moderate-size bee. It occurs in the United States and southern Canada east of the Rocky Mountains. It is common and sometimes abundant in Minnesota.

Golden sweat bees are primitively eusocial. Like eusocial bees, they live in colonies that include a queen and non-reproductive workers. However, there is little morphological difference between the queen and the workers, and the colonies are short-lived. Adults are active from May through September. They are found in a variety of habitats, including grasslands, old fields, hardwood forests, and croplands, and around human buildings.

Until recently, these were treated as two distinct species: Augochlorella striata, the larger, eastern species; and Augochlorella aurata, the smaller, widespread species. They were differentiated by their size; by the shape, coarseness, and density of pitting (punctation) of the propodeum; and by the length of certain hairs on the legs of the male. A recent review of the genus Augochlorella (Coelho, B. W. T. 2004) concluded that the differences were not enough to justify separation. Augochlorella striata became a synonym of Augochlorella aurata. As a result, as currently recognized, Augochlorella aurata is highly variable in size and morphology.

Adults are 3⁄16″ to ¼″ (5 to 7 mm) in length. Females tend to be larger than males. The entire body is brilliant metallic green, sometimes tinged with blue, coppery, or red.

The head and thorax are covered with very short, pale yellowish hairs above, whitish hairs below. There are two large compound eyes on the sides of the head and three simple eyes (ocelli) in a triangle on top of the head. The inner margin of the compound eyes is shallowly indented toward the top. The antennae are black. A single line-like groove extends downward from the base of each antenna (subantennal suture). The tongue is short. The plate on the face (clypeus) is shiny above and black on the lower third or half.

The rear face of the thorax (propodeum), anatomically first segment of the abdomen, is smoothly rounded, with no sharp ridges at the top or on the sides.

The wings are clear and lightly tinted smoky brown, and the veins are dark. On the forewing, the cell on the leading edge (stigma) dark. There are three submarginal cells, the first one longer than the third. The basal vein is strongly curved (arced) inward. The lobe at the base of the hindwing (jugal lobe) is longer than the submedian cell.

The legs are green, brown, and brownish black with short hairs. The female has a dense patch of longer, branched hairs (scopa) used to collect pollen, on the fourth segment (tibia). The male lacks this modification.

Total length: 3⁄16″ to ¼″ (5 to 7 mm)

A variety of habitats, including grasslands, old fields, hardwood forests, and croplands, and around human buildings

Three generations per year: May through September (CCESR)

The last brood of females overwinters in the nest, effectively a hibernaculum. They become the foundresses and queens of new nests in the spring.

Pollen and nectar

4, 27, 29, 30, 82, 83.

Common, sometimes locally abundant

Augochlorella aurata
Sam Droege

Green Sweat Halictid Bee (Augochlorella aurata
Andrée Reno Sanborn

Babette Kis
5/13/2024

Location: Barnes Prairie, Racine Co., WI

Augochlorella aurata, golden sweat bee, photographed at Barnes Prairie, Racine Co., WI. on May 13, 2024.