I've spotted solitary bees in the garden this year similar to these little guys, but they always disappeared before I was able to get the camera. these four seem to have overnighted in the centre of a hollyhock bloom. They are quite colourful with their irdescent green head and thorax.

Metallic Green Bee - Agapostemon virescens

SWEAT BEES (Halictidae, Halictinae, Halictini)

Augochlora pura, Agapostemon splendens, A. sericeus, A. virescens, Lasioglossum

vierecki, L. bruneri, L. versatum

An abundant group of bees around farms, sweat bees tend to be small and bright

metallic green/blue (Augochlora pura) or a dull metallic brown on head/thorax with

bands of hair on the abdomen (Lasioglossum vierecki). All carry pollen on special long

hairs on their hind legs and nest in both cavities and in the ground. Some sweat bees

are solitary, and often quite small in size. There is usually only a single generation per

year. A few species are social and have one to a few queens, supported by a number of

female workers and produce multiple generations per year. Halictid bees are common

and are good pollinators of crops and wildflowers.

Note: The common name ‘sweat bee’ derives from some species having an affinity for

the salt in human sweat.