the only member of the genus that dig their own nests, Chlorion aerarium is most common in loose gravelly or sandy soil, and is not as attached to human habitations as the two common mud daubers C. californicum and Scelifron caementarium.
Differs from the superficially similar Chalybion as follows:
Tarsal rake (females only)
Head and thorax sparsely hairy
Propodeum with U-shaped dorsal enclosure defined at least posteriorly by a semicircular sulcus/furrow (Chalybion has at most a median sulcus or pit)
the head is more produced at the temples and vertex (different head shape)
...Note greenish or purplish color of many Chlorion vs. blue in Chalybion. The shape of the pronotoum is more strongly notched in Chalybion; ...the head of Chlorion is broader.
C. aerarium preys on crickets, C. cyaneum on cockroaches