Silver Bees are large, robust bees, with grey-black coloration. They have two sets of transparent wings with black veins. The front set of wings is larger than the hind set. Females have pollen baskets on their hind legs. The body is covered with silver-grey hair; the body color below the hairs is black.
Similar species: Silver Bees may be confused with Bembix wasps. Bembix wasps have shiny, smooth, abdomens, with white to blue-yellow stripes, whereas Silver Bees have a fuzzy abdomen with grey stripes. Bembix wasps dig by rapidly flicking the sand backwards, Silver Bees do not flick the sand (they dig with sweeping movements of their legs). Silver bees also look shorter and fatter with black eyes, while Bembix wasps are long and narrow with blue-green eyes.
Silver Bees overwinter underground as adults. Males emerge first in the spring, as early as February or March, and begin to look for females. Soon after the first males appear, females emerge from the ground and mate. Mating is often a big group of males fighting over the female, and wrestling on the ground. After mating, females begin to dig nests in the soil. Each female bee digs her own nest, but they tend to nest in groups, and usually many nest entrances (holes) will be seen in one area. Each nest starts as one tunnel, which branches underground into a few side tunnels. At the end of each of these tunnels she creates a space called the “brood cell,” where she stores pollen and nectar from the flowers she visits. After the brood cell is filled with a ball of pollen and nectar, the female will lay an egg, fill the tunnel with soil, and then begin a new tunnel. Fertilized eggs turn into females and unfertilized eggs, usually produced late in the season, become males. A female bee will continue to create tunnels, provision brood cells and lay eggs until she dies. By the end of the season, around early July, all adult bees die. The eggs laid during the season will hatch, eat and develop into larvae, then into pupae and finally into adult bees. These new adult bees will remain underground, in a state called “diapause,” through the winter until spring comes again.
Nest entrances are fragile and can collapse easily. Please watch where you step while monitoring!
There is currently no photoguide available for this species. If you'd like help us create one, use the guidance document and species template provided here. Then send it via email to education@usanpn.org when it is complete.
