Anthidium atripes

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Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Anthidiini
Genus: Anthidium Fabricius, 1804
Subgenus: A. (Anthidium) Fabricius, 1804
Species: Anthidium atripes Cresson, 1879
Common name: none

Overview

Anthidium (Anthidium) atripes have black integument with cream or yellow-colored maculations (Gonzalez and Griswold 2013). Females have black pubescence on their legs and white hairs on the frons, vertex, pronotal lobe, scutum, scutellum, axilla, and side of T1 and T2. Females range in body length from 7.7–11.5 mm (Gonzalez and Griswold 2013). Males have black pubescence on their gena and legs, and white hairs on their head and thorax. Males range in body length from 10.8–14.5 mm (Gonzalez and Griswold 2013). Originally A. atripes was classified as a variety of Anthidium emarginatum (Schwarz 1928).

Diagnostic characteristics

(modified from Gonzalez and Griswold 2013)

• Female clypeus without hooked or curly hairs on disc.
• Female fore basitarsus is covered with short, semi-erect, unbranched hairs as well as dense, long tomentum, which cause the segment to appear robust.
• Female hind tibia without anterior carina.
• Female labrum with two preapical projections and without basal protuberances.
• Female mandible with six teeth and without maculations.
• Female scopa dark brown to black.
• Female depressed marginal zones of T3–T5 are weakly punctate and lack smooth, shiny distal margins.
• Female T5 and T6 lack maculations.
• Female T6 with distal margin nearly truncate and apical rim depressed.
• Male S4 has a broad, black brush with a concave margin.
• Male S6 apex of median lobe is incised, and lateral lobes are low or absent.
• Male S8 bifid apically.
• Male T7 lateral lobe is long and narrow.

May be confused with

Anthidium atripes may be confused with A. atripoides based on similar lengths, the depressed marginal zone of T3 to T5 with sparse punctation, and a lack of smooth, shiny distal margins (Gonzalez and Griswold 2013). Female A. atripes can be differentiated from A. atripoides by the presence of dense, long tomentum on the mid and fore basitarsus and the thin apical margin of the clypeus in A. atripes (Gonzalez and Griswold 2013). Male A. atripes can be differentiated from A. atripoides by the presence of a broad lateral lobe on T7, a concave brush on the distal margin of S4, and an incised apex on the median lobe of S6 in A. atripes (Gonzalez and Griswold 2013).

Phenology

Anthidium atripes adults have been recorded in flight from May to July; however, a single record was documented on three separate occasions in late August, mid-September, and early November. Peak activity occurs from the last half of May to early July (Gonzalez and Griswold 2013).

Host associations

Anthidium atripes is a generalist that has been observed visiting a variety of species of Asteraceae, Boraginaceae, Brassicaceae, Fabaceae, Malvaceae, Plantaginaceae, and Polemoniaceae (Gonzalez and Griswold 2013).

Nesting behavior

Nesting behavior is unknown.

Distribution

Anthidium atripes occur throughout the western U.S., from southern California along the northeastern side of the Sierra Nevada Mountains, to eastern Oregon, southern Idaho, western Colorado, and west Texas (Gonzalez and Griswold 2013). They are absent in Arizona and New Mexico. Anthidium atripes also occurs in Baja California, Mexico (Gonzalez and Griswold 2013). They are primarily found between 1,100–3,200 m in elevation within the Rocky Mountains, and are absent in desert and forest ecosystems (Gonzalez and Griswold 2013).

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