I’ve just added a new illustration of the Catalina Lady Beetle (Delphastus catalinae) and redrawn illustrations of the Whitefly Predator (Delphastus pusillus) and Pale Whitefly Predator (Delphastus pallidus). These small beetles (under 2mm long) play a large part in biocontrol of whiteflies. Two additional western species are nearly indistinguishable from the Whitefly Predator (in fact, they were once believed to be the same species), but in the east, genus Delphastus can be told apart by color.
The most common and widespread species is the Whitefly Predator, a very dark brown or black beetle with small pale areas on the pronotum. It ranges from New England to Central Florida and west to the Great Plains. (It was formerly believed to occur from coast to coast, until the two western species were split from it. For the record, those are Delphastus sonoricus and Delphastus dejavu.)
Also native to eastern North America is the Pale Whitefly Predator, a light- to medium-brown species whose range is limited to Florida. It is evenly colored all over, with no darker or lighter areas on the pronotum.
The Catalina Lady Beetle is native to California, but has been introduced to eastern North America for biocontrol. Though widely released, it has only become permanently established in the southern U.S. Its color is midway between the other two species, a medium- to dark brown, with the center of the pronotum somewhat darker, but no distinctly pale areas on the pronotal margins.
All three species eat whiteflies, and are often found in manmade plantings such as greenhouses, arboreta, and agricultural areas, where they have been released or naturalized for biocontrol. Their natural habitat is poorly known, but probably includes herbacious plants and bushes that whiteflies feed on. As “LBLBs” (little brown lady beetles) go, they are fairly distinctive, with their rotund shape and glossy surface. Most other LBLBs are elongated and oval in shape, hairy, or both. Plus, any small lady beetle that you encounter feeding on whiteflies is almost certainly Delphastus!