Numbers
Nearctica lists 21 species.
Identification
The easiest method of separating Ceratina from Xylocopa is by size: Ceratina are less than 8 mm in length whereas Xylocopa are 20 mm or larger. In addition, Ceratina has the second submarginal cell about as high as wide basally, whereas in Xylocopa it is about half as high as wide basally.
According to
(1) C. (Zadontomerus) dupla may serve as an example: Body bluish green, clypeus with oblong, median maculation; antennae brownish basally, spurs pale yellow. Adults visit raspberry and goldenrod flowers particularly but also many others. They nest in Sumac and elder stems.
Life Cycle
They excavate nests with their mandibles in the pith of broken or burned plant twigs and stems. Females overwinter as adults in partially or completely excavated stems. In the spring, this resting place (hibernaculum) is modified into a brood nest by further excavation.
Remarks
Features that help with ID of this genus (according to Eric Eaton): club-shaped abdomen, dull metallic color and inconspicuous hair.
Males have larger white markings on the face.
