Anthidium formosum

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Anthidiini
Genus: Anthidium Fabricius, 1804
Subgenus: A. (Anthidium) Fabricius, 1804
Species: Anthidium formosum Cresson, 1878
Common name: none

Overview

Anthidium (Anthidium) formosum are dark brown to black with yellow maculations (Gonzalez and Griswold 2013). Females have yellow to ferruginous pubescence, sometimes with white pubescence on the sides of the thorax and abdomen, and have a body length of 11.5–13.5 mm (Gonzalez and Griswold 2013). Males have white pubescence on their head and thorax, and range in length from 12.8–15.4 mm (Gonzalez and Griswold 2013).

Diagnostic characteristics

(modified from Gonzalez and Griswold 2013)

May be confused with

Anthidium formosum may be confused with A. illustre based on the large body size, female T6 distal margin with a deep median emargination, and elongate male penis valves (Gonzalez and Griswold 2013). Both sexes of Anthidium formosum can be differentiated from A. illustre by the lack of preapical projections on the labrum (Gonzalez and Griswold 2013). Male A. formosum can also be differentiated from A. illustre by the shape of S4 and S6 (Gonzalez and Griswold 2013).

Phenology

Anthidium formosum adults have been recorded in flight from May to September, with peak activity occurring from the last half of June to the first half of August (Gonzalez and Griswold 2013).

Host associations

Anthidium formosum is a generalist that has been observed visiting a variety of species within Asteraceae, Boraginaceae, Fabaceae, Lamiaceae, Orobanchaceae, and Ranunculaceae (Gonzalez and Griswold 2013).

Nesting behavior

Anthidium formosum nesting biology was determined from trap nests (Horning 1969; Parker 1987). Nests plugs are constructed out of a variety of materials, ranging from only trichomes to trichomes with pebbles, small pieces of wood, masticated plant material, or lizard dung (Krombein 1967). Horning (1969) also observed resin in the nest plugs of three A. formosum nests in Idaho.

Distribution

Anthidium formosum occur throughout California, Oregon, Washington, Montana, Wyoming, and Colorado. They are found primarily in the Great Basin, Snake-Columbia, and Wyoming Basin shrub steppe; Colorado Plateau shrublands; Wasatch, Uinta, and Great Basin montane forests; and eastern Cascades and Sierra Nevada forests (Gonzalez and Griswold 2013).


​Distribution map generated by Discover Life -- click on map for details, credits, and terms of use.

<p><em>Anthidium formosum</em> female face, photo: Chelsey Ritner</p>
Anthidium formosum female face, photo: Chelsey Ritner
<p><em>Anthidium formosum</em> female lateral habitus, photo: Chelsey Ritner</p>
Anthidium formosum female lateral habitus, photo: Chelsey Ritner
<p><em>Anthidium formosum</em> female abdomen, photo: Chelsey Ritner</p>
Anthidium formosum female abdomen, photo: Chelsey Ritner
<p><em>Anthidium formosum</em>, dorsal view of sixth tergum (T6), photo: Chelsey Ritner</p>
Anthidium formosum, dorsal view of sixth tergum (T6), photo: Chelsey Ritner
<p><em>Anthidium formosum</em> female, diagram showing the dorsal view of the sixth tergite (T6), diagram from Gonzalez and Griswold 2013</p>
Anthidium formosum female, diagram showing the dorsal view of the sixth tergite (T6), diagram from Gonzalez and Griswold 2013
<p><em>Anthidium formosum</em> male face, photo: Chelsey Ritner</p>
Anthidium formosum male face, photo: Chelsey Ritner
<p><em>Anthidium formosum</em> male lateral habitus, photo: Chelsey Ritner</p>
Anthidium formosum male lateral habitus, photo: Chelsey Ritner
<p><em>Anthidium formosum</em> male abdomen, photo: Chelsey Ritner</p>
Anthidium formosum male abdomen, photo: Chelsey Ritner
<p><em>Anthidium formosum</em> male, ventral view of fourth sternum (S4), photo from Gonzalez and Griswold 2013</p>
Anthidium formosum male, ventral view of fourth sternum (S4), photo from Gonzalez and Griswold 2013
<p><em>Anthidium formosum</em> male, dorsal view of seventh tergum (T7), photo: Chelsey Ritner</p>
Anthidium formosum male, dorsal view of seventh tergum (T7), photo: Chelsey Ritner
<p><em>Anthidium formosum</em> male, diagram showing dorsal view of seventh tergum (T7), diagram from Gonzalez and Griswold 2013</p>
Anthidium formosum male, diagram showing dorsal view of seventh tergum (T7), diagram from Gonzalez and Griswold 2013
<p><em>Anthidium formosum</em> male, diagram showing ventral view of sixth sternum (S6), diagram from Gonzalez and Griswold 2013</p>
Anthidium formosum male, diagram showing ventral view of sixth sternum (S6), diagram from Gonzalez and Griswold 2013
<p><em>Anthidium formosum</em> male, diagram showing ventral view of seventh sternum (S7), diagram from Gonzalez and Griswold 2013</p>
Anthidium formosum male, diagram showing ventral view of seventh sternum (S7), diagram from Gonzalez and Griswold 2013
<p><em>Anthidium formosum</em> male, diagram showing ventral view of eighth sternum (S8), diagram from Gonzalez and Griswold 2013</p>
Anthidium formosum male, diagram showing ventral view of eighth sternum (S8), diagram from Gonzalez and Griswold 2013
<p><em>Anthidium formosum </em>nest</p>
Anthidium formosum nest
<p><em>Anthidium formosum </em>nest</p>
Anthidium formosum nest