Numbers
2 spp. in our area
(2), 20 total
(3)
1. C. aerarium: transcontinental (s. Canada south to Mexico)
2. C. cyaneum: AZ, NM, TX; Mexico
Identification
One of two genera in our area notable for their distinctively metallic-blue bodies. Chlorion differs from the superficially similar Chalybion as follows:
Head and thorax sparsely hairy, the vertex of the head particularly lacking dense setae
Antennae inserted lower, well below the halfway point of the eye.
The head is more produced at the temples and vertex (different head shape)
Mandibles are dentate rather than simple and sickle-shaped
Pronotum not as strongly notched
Tarsal rake present (females only)
Wing with the hind margin of the third sub-marginal cell meeting the marginal cell at nearly the same point as the fore margin, resulting in a strongly triangular cell rather than a rhombic cell
Propodeum with U-shaped dorsal enclosure defined at least posteriorly by a semicircular sulcus/furrow (Chalybion has at most a median sulcus or pit)
Generally larger
Key to Species
C. aerarium: male face without silvery pubescence; female mesopleuron smooth between punctures, pronotum and scutum with fine scattered punctures
C. cyaneum: male face with silvery pubescence; female mesopleuron wrinkled between punctures, pronotum and scutum with coarse, dense punctures anteriorly
Life Cycle
ground-nesting (
Chalybion & Sceliphron build mud nests). Both
Chl. aerarium and
Chl. cyaneum dig their own nests, commonly in loose gravel or sandy soil;
Chl. aerarium will occasionally make use of pre-existing burrows. Only after the nest has been constructed does the female hunt and provision the nest. Old World congeners use only pre-existing burrows.
(5)