Anthidium emarginatum

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Anthidiini
Genus: Anthidium Fabricius, 1804
Subgenus: A. (Anthidium) Fabricius, 1804
Species: Anthidium emarginatum (Say, 1824)
Common name: none

Overview

Anthidium (Anthidium) emarginatum are primarily black with ivory or yellow maculations and dark brown antennae, mandible, and legs (Gonzalez and Griswold 2013). Females have dark brown to black pubescence, except for white or yellow hairs on the frons, vertex, gena, scutum, pronotal lobe, dorsum of the mesepisternum and metepisternum, and terga. Females have a body length of 8.3–10.8 mm (Gonzalez and Griswold 2013). Males have white pubescence, except for yellow to light brown hairs on the inner tarsi. The sterna either have dark brown to black hairs, or are entirely white to yellow. Males range in body length from 9.4–11.1 mm (Gonzalez and Griswold 2013).

Diagnostic characteristics

​(modified from Gonzalez and Griswold 2013)

May be confused with

Female A. emarginatum with dark hair and ivory markings can appear similar to female A. atrifrons. They appear similar due to the presence of a black scopa and weakly elevated discal areas on the terga. Anthidium emarginatum can be differentiated from A. atrifrons by the sparser tomentum on the fore basitarsus, and the apical rim on T6 that is depressed across the entire width of the tergum. Additionally, A. emarginatum and A. atrifrons appear to have different elevation preferences. Anthidium emarginatum can be found in lowland environments, while A. atrifrons are often found in montane habitats (Gonzalez and Griswold 2013).

Female A. emarginatum may also be confused with A. tenuiflorae due to the dark scopa; however, they can be differentiated by the lack of light maculations on the scutellum. Male A. emarginatum may also be confused with A. tenuiflorae due to the narrow T7 with a semicircular emargination. They can be differentiated by T6 lateral lobe shape and S8 apical process (Gonzalez and Griswold 2013).

Phenology

Anthidium emarginatum adults have been recorded in flight from late March to early September, with peak activity occurring from the last half of May to the first half of July (Gonzalez and Griswold 2013).

Host associations

Anthidium emarginatum is a generalist that has been observed visiting a variety of species within Asteraceae, Boraginaceae, Brassicaceae, Cactaceae, Fabaceae, Lamiaceae, Loasaceae, Malvaceae, Plantaginaceae, Polemoniaceae, Rosaceae, and Solanaceae (Gonzalez and Griswold 2013).

Nesting behavior

Previously, A. emarginatum and A. atrifrons were considered the same species. Nesting observations were recorded for a specimen which 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).

Distribution

Anthidium emarginatum occur throughout eastern California, Oregon, and Washington east to Montana, Wyoming, western Nebraska, western Kansas, New Mexico, and western Texas. They are found primarily in grasslands, Colorado Plateau shrublands, shrub steppe, and the Chihuahuan desert (Gonzalez and Griswold 2013).


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

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