Anthidium (Anthidium) atrifrons females vary greatly in their coloration. The face, scutum, and legs can be entirely black, somtimes with ivory to yellow on the mandible, scutum, legs, and rarely the clypeus (Gonzalez and Griswold 2013). In females, the hairs on the sternal scopa and legs range from a black or dark brown coloration to white. Females range in body length from 7.5–10 mm, and males can range in body length from 11.5–13.1 mm (Gonzalez and Griswold 2013).
(modified from Gonzalez and Griswold 2013)
Female A. atrifrons with dark hair and ivory markings can appear similar to A. emarginatum, whereas forms with pale hair and strong yellow markings may be confused with A. tenuiflorae, A. collectum, or A. duomarginatum. Female A. atrifrons can be differentiated from the other species by the denser tomentum on the fore basitarsus, as well as the depressed apical rim of T6 that progressively dissipates until absent about halfway between the lateral angle and the median emargination (Gonzalez and Griswold 2013). Male A. atrifrons may appear similar to A. dammersi because of the similarly shaped T7, but can be differentiated by the shapes of the lateral lobes of S6 and T7 (Griswold and Gonzalez 2013).
Additionally, A. emarginatum and A. atrifrons appear to have different elevation preferences. Anthidium atrifrons are often found in montane habitats, while A. emarginatum can be found in lowland environments (Gonzalez and Griswold 2013).
Anthidium atrifrons adults have been recorded in flight from April to October, with peak activity occurring from June to early August (Gonzalez and Griswold 2013).
Anthidium atrifrons is a generalist that has been observed visiting a variety of species of Apiaceae, Asteraceae, Boraginaceae, Brassicaceae, Caprifoliaceae, Caryophyllaceae, Crassulaceae, Fabaceae, Lamiaceae, Onagraceae, Plantaginaceae, Polemoniaceae, Polygonaceae, and Rosaceae. Anthidium atrifrons has shown a strong preference for Phacelia (Boraginaceae), with visits occurring at 64%. Anthidium atrifrons also collects trichomes from two Asteraceae species, Pseudognaphalium canescens and P. stramineum, to line their nests and create nest plugs (Davidson 1895).
A. atrifrons and A. emarginatum were, at one time, considered the same species. The specimen associated with these nesting observations can no longer be located, preventing the identification of the species. Therefore, it is equally likely that the nesting observations correspond to either species. The recorded observations found the species nests in the ground in abandoned Anthophora (Apidae) nests (Davidson 1895). Cell partitions and nest plugs are comprised of trichomes from two Asteraceae species: Pseudognaphalium canescens and P. stramineum (Davidson 1895).
Anthidium atrifrons occur throughout the western U.S., primarily in montane habitats (Gonzalez and Griswold 2013).