Anthidium (Anthidium) collectum are dark brown to black with yellow maculations (Gonzalez and Griswold 2013). Females have white pubescence, except for the yellow to brown hairs found on the vertex, scutum, axilla, scutellum, inner tarsi, terga, and S6. Females range in body length from 8.5–9.7 mm (Gonzalez and Griswold 2013). Males have pale pubescence on the vertex, scutum, scutellum, and terga. Males range in body length from 10.0–13.8 mm (Gonzalez and Griswold 2013).
(modified from Gonzalez and Griswold 2013)
Female A. collectum may be confused with A. labergei due to the basitarsi covered with dense tomentum, white sternal scopa, and dull terga with dense punctation (Gonzalez and Griswold 2013). Female A. collectum and A. labergei can be differentiated from one another by the presence of yellow maculations on the outer surface of the mandible, a more convex clypeus in profile with a wavy distal margin, and T6 with a depressed apical rim that is visible along three-quarters of the distal margin (Gonzalez and Griswold 2013). Male A. collectum may be confused with A. schwarzi due to the narrowly rounded lateral lobe of T7, S4 with a similar median apical brush of black hairs, and S6 with a median, small, apically notched median lobe (Gonzalez and Griswold 2013). Male A. collectum can be differentiated from A. schwarzi by the narrower lateral lobe on T7, a less concave distal margin on S4, and shorter hairs on the S4 apical brush (Gonzalez and Griswold 2013).
Anthidium collectum adults have been recorded in flight from March to early August, with peak activity occurring from April to June (Gonzalez and Griswold 2013).
Anthidium collectum are generalists that have been observed visiting a variety of species within Adoxaceae, Asteraceae, Boraginaceae, Fabaceae, Lamiaceae, Onagraceae, Phrymaceae, Polemoniaceae, Salicaceae, Solanaceae, and Violaceae (Gonzalez and Griswold 2013). However, they have a strong preference for Lotus (Fabaceae) and Phacelia (Boraginaceae) (Gonzalez and Griswold 2013).
Anthidium collectum nest in preexisting cavities in hollow stems or in abandoned ground nests of other bees (Gonzalez and Griswold 2013). Nest plugs are comprised of trichomes from Artemisia tridentata (Asteraceae) and pebbles (Hicks 1929; Ferguson 1962).
Anthidium collectum occur in primarily in California but a small number of specimens have been reported from Oregon, Washington, Idaho, and Kansas (Gonzalez and Griswold 2013). They are found at lower elevations in grasslands, chaparral, woodlands, and occasionally in coastal and forest landscapes (Gonzalez and Griswold 2013).