|Sweat bee on hand - REK|
The first vote from Bi-State Bugs was Lasioglossum sp. This is the largest bee genus with 1700 species. Most are slender and 50% are dull to metallic black, while others are metallic green, blue or purple. Most are solitary and ground dwelling but there are many outliers that are found in rotting wood and a few that form colonies.
Sweat bees in general are in the family Halictidae. They are attracted to our sweat possibly for the salt although they also seem to like hanging on the rims cans and glasses of soft drinks. This is where most stings occur. The females are the ones capable of stinging but only when disturbed and the sting is mild, a 1 on the Schmidt Sting Pain Index.* They can hang on and inject more toxin so brush them off quickly.
Prior to the introduction of the European honey bee, these were our most numerous pollinators, and they continue to play an important role. Especially as the honey bee is facing declining numbers with colony collapse, sweat bees are very important pollinators for wildflowers and crops, so try to politely brush them away to find another source of sugar than your drink.
* More background on the Schmidt Index in Wikipedia.