Anthidium atrifrons

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Anthidiini
Genus: Anthidium Fabricius, 1804
Subgenus: A. (Anthidium) Fabricius, 1804
Species: Anthidium atrifrons Cresson, 1868
Common name: none

Overview

Anthidium (Anthidium) atrifrons females vary greatly in their coloration. The face, scutumscutum:
the large segment on top of the thorax located between the wings and behind the head
, and legs can be entirely black, somtimes with ivory to yellow on the mandiblemandible:
bee teeth, so to speak, usually crossed and folded in front of the mouth
, scutumscutum:
the large segment on top of the thorax located between the wings and behind the head
, legs, and rarely the clypeusclypeus:
a section of the face below the antennae, demarcated by the epistomal sutures
(Gonzalez and Griswold 2013Gonzalez and Griswold 2013:
Gonzalez, V.H. and T.L. Griswold. 2013. Wool carder bees of the genus Anthidium in the Western Hemisphere (Hymenoptera: Megachilidae): diversity, host plant associations, phylogeny, and biogeography. Zoological Journal 168: 221ndash;425.). In females, the hairs on the sternal scopascopa:
modified hairs for carrying pollen; often branched and dense hairs on the hind-leg, or on the ventral surface of the abdomen in Megachilidae
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 2013Gonzalez and Griswold 2013:
Gonzalez, V.H. and T.L. Griswold. 2013. Wool carder bees of the genus Anthidium in the Western Hemisphere (Hymenoptera: Megachilidae): diversity, host plant associations, phylogeny, and biogeography. Zoological Journal 168: 221ndash;425.).

Diagnostic characteristics

(modified from Gonzalez and Griswold 2013Gonzalez and Griswold 2013:
Gonzalez, V.H. and T.L. Griswold. 2013. Wool carder bees of the genus Anthidium in the Western Hemisphere (Hymenoptera: Megachilidae): diversity, host plant associations, phylogeny, and biogeography. Zoological Journal 168: 221ndash;425.)

• Female clypeusclypeus:
  a section of the face below the antennae, demarcated by the epistomal sutures
  is entirely black and prominently convexconvex:
  curved outward
  when viewed in profile.
• Female hind tibiatibia:
  the segment of the leg, between the femur and the tarsus
  without anterioranterior:
  toward the head or on the head side of a segment being described
  carina.
• Female labrumlabrum:
  part of the head abutting the clypeus, folds down in front of the mouthparts
  with two large preapicalpreapical:
  referring to a section of a bee that is physically found just before the outermost (or apical) end of the section or segment
  projections and without basalbasal:
  originating at the foundation of a structure
  protuberances.
• Female fore basitarsusbasitarsus:
  the segment of the tarsus that is the nearest to the body of the bee, usually the largest of all the tarsal segments
  is covered with dense, long tomentumtomentum:
  a form of pubescence composed of short matted, woolly hair
  , and short, semi-erect, unbranched hairs.
• Female T1–T5 discal area punctures are 1–3 puncture widths apart, the integumentintegument:
  a tough, protective outer layer
  somewhat shiny in between the punctures.
• Female T1–T5 depressed marginal area densely punctatepunctate:
  studded with tiny holes
  medially, punctures less than one puncture width apart.
• Female T6T6:
  the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
  has a distinct median emarginationemargination:
  a notched or cut out place in an edge or margin, can be dramatic or simply a subtle inward departure from the general curve or line of the margin or structure being described
  , a narrowly depressed apicalapical:
  near or at the apex or end of any structure
  rim, and an indistinct laterallateral:
  relating, pertaining, or attached to the side
  angle.
• Male S4S4:
  the plates on the underside of the abdomen, often abbreviated when referring to a specific segment to S1, S2, S3, S4, S5, S6, S7, or S8
  with median apicalapical:
  near or at the apex or end of any structure
  brush broad, and with dense black hairs. The apicalapical:
  near or at the apex or end of any structure
  margin of S4S4:
  the plates on the underside of the abdomen, often abbreviated when referring to a specific segment to S1, S2, S3, S4, S5, S6, S7, or S8
  is nearly straight medially.
• Male S6S6:
  the plates on the underside of the abdomen, often abbreviated when referring to a specific segment to S1, S2, S3, S4, S5, S6, S7, or S8
  with laterallateral:
  relating, pertaining, or attached to the side
  projections and sublateral carinae.
• Male S7S7:
  the plates on the underside of the abdomen, often abbreviated when referring to a specific segment to S1, S2, S3, S4, S5, S6, S7, or S8
  with apicalapical:
  near or at the apex or end of any structure
  margin somewhat truncatetruncate:
  ending abruptly, or squared off
  .
• Male T7T7:
  the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
  laterallateral:
  relating, pertaining, or attached to the side
  lobe rounded to subtriangular.

May be confused with

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 tomentumtomentum:
a form of pubescence composed of short matted, woolly hair
on the fore basitarsusbasitarsus:
the segment of the tarsus that is the nearest to the body of the bee, usually the largest of all the tarsal segments
, as well as the depressed apicalapical:
near or at the apex or end of any structure
rim of T6T6:
the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
that progressively dissipates until absent about halfway between the laterallateral:
relating, pertaining, or attached to the side
angle and the median emarginationemargination:
a notched or cut out place in an edge or margin, can be dramatic or simply a subtle inward departure from the general curve or line of the margin or structure being described
(Gonzalez and Griswold 2013Gonzalez and Griswold 2013:
Gonzalez, V.H. and T.L. Griswold. 2013. Wool carder bees of the genus Anthidium in the Western Hemisphere (Hymenoptera: Megachilidae): diversity, host plant associations, phylogeny, and biogeography. Zoological Journal 168: 221ndash;425.). Male A. atrifrons may appear similar to A. dammersi because of the similarly shaped T7T7:
the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
, but can be differentiated by the shapes of the laterallateral:
relating, pertaining, or attached to the side
lobes of S6S6:
the plates on the underside of the abdomen, often abbreviated when referring to a specific segment to S1, S2, S3, S4, S5, S6, S7, or S8
and T7T7:
the segments on the top side of the abdomen, often abbreviated when referring to a specific segment to T1, T2, T3, T4, T5, T6, or T7
(Griswold and Gonzalez 2013Gonzalez 2013:
Gonzalez, V.H. 2013. Taxonomic comments on Megachile subgenus Chrysosarus (Hymenoptera: Megachilidae). Journal of Melittology 5: 1ndash;6.).

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 2013Gonzalez and Griswold 2013:
Gonzalez, V.H. and T.L. Griswold. 2013. Wool carder bees of the genus Anthidium in the Western Hemisphere (Hymenoptera: Megachilidae): diversity, host plant associations, phylogeny, and biogeography. Zoological Journal 168: 221ndash;425.).

Phenology

Anthidium atrifrons adults have been recorded in flight from April to October, with peak activity occurring from June to early August (Gonzalez and Griswold 2013Gonzalez and Griswold 2013:
Gonzalez, V.H. and T.L. Griswold. 2013. Wool carder bees of the genus Anthidium in the Western Hemisphere (Hymenoptera: Megachilidae): diversity, host plant associations, phylogeny, and biogeography. Zoological Journal 168: 221ndash;425.).

Host associations

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 1895Davidson 1895:
Davidson, A. 1895. The habits of Californian bees and wasps. Anthidium emarginatum, its life history and parasites. Entomological News 6: 252ndash;253.).

Nesting behavior

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 1895Davidson 1895:
Davidson, A. 1895. The habits of Californian bees and wasps. Anthidium emarginatum, its life history and parasites. Entomological News 6: 252ndash;253.). Cell partitions and nest plugs are comprised of trichomes from two Asteraceae species: Pseudognaphalium canescens and P. stramineum (Davidson 1895Davidson 1895:
Davidson, A. 1895. The habits of Californian bees and wasps. Anthidium emarginatum, its life history and parasites. Entomological News 6: 252ndash;253.).

Distribution

Anthidium atrifrons occur throughout the western U.S., primarily in montane habitats (Gonzalez and Griswold 2013Gonzalez and Griswold 2013:
Gonzalez, V.H. and T.L. Griswold. 2013. Wool carder bees of the genus Anthidium in the Western Hemisphere (Hymenoptera: Megachilidae): diversity, host plant associations, phylogeny, and biogeography. Zoological Journal 168: 221ndash;425.).

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

References

Davidson, A. 1895. The habits of Californian bees and wasps. Anthidium emarginatum, its life history and parasites. Entomological News 6: 252-253.

Gonzalez, V.H. and T.L. Griswold. 2013. Wool carder bees of the genus Anthidium in the Western Hemisphere (Hymenoptera: Megachilidae): diversity, host plant associations, phylogeny, and biogeography. Zoological Journal of the Linnean Society 168: 221-425.