Anthidium

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Anthidiini
Genus: Anthidium Fabricus, 1804
Subgenera: Anthidium, Gulanthidium, Nivanthidium, Proanthidium, Severanthidium, Turkanthidium
Common name: wool carder bees

Overview

Anthidium are commonly referred to as “wool carder bees” because females scrape trichomes off leaves and stems with their mandibles to use as nesting material (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.; Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). Anthidium generally have robust bodies with broad, flattened, and parallel-sided abdomens. Their integumentintegument:
a tough, protective outer layer
is black with conspicuous yellow maculations (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). They range in body length from 6–19 mm (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). Unlike many other bees, males are generally larger than females (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.).

Diversity

Anthidium contains more than 160 species in six subgenera worldwide (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.). There are 36 species that occur within the U.S and Canada (Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.) and 28 species that occur in Mexico. All North American species are in the subgenus Anthidium except for the invasive species A. oblongatum, which is in the subgenus Proanthidium. The greatest diversity of Anthidium is thought to occur in the Great Basin (24 species) and on the Colorado Plateau (23 species) (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 Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp., unless otherwise stated)

• Arolia absent.
• Middle tibiatibia:
  the segment of the leg, between the femur and the tarsus
  apicalapical:
  near or at the apex or end of any structure
  projection with one spine.
• Mandiblemandible:
  bee teeth, so to speak, usually crossed and folded in front of the mouth
   with five or more teeth. The number of teeth is variable across species and sometimes even within species. (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.).
• Propodeum propodeum:
  the last segment of the thorax
  without foveafovea:
  a depressed region of cuticle; in bees this depressed area is usually only very slightly hollow and usually on the face.
  defined by a carinacarina:
  a clearly defined ridge or keel, not necessarily high or acute; usually appears on bees as simply a raised line
  behind spiraclespiracle:
  a breathing pore, usually occurring on the third thorasic segment
  .
• Scutellum scutellum:
  shield shaped plate behind scutum
  distinctly overhanging metanotummetanotum:
  the posterior dorsal segment of the thorax, behind the scutellum
  .
• T1–T6 with depressed marginal zone, often with finer and closer punctationpunctation:
  overall pattern of the punctures on a surface of a bee, includes size of punctures and the distance between them
  than the rest of the tergumtergum:
  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
  .
• 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
  with apicalapical:
  near or at the apex or end of any structure
  depressed rim with median apicalapical:
  near or at the apex or end of any structure
  notch, sometimes hidden by hairs.
• Male gonostyligonostyli:
  the apical-most appendage of the male genitalia, which is usually quite hairy
  club- or finger-shaped and hairy.
• Male penis valves are often longer than or the same size as the gonostyligonostyli:
  the apical-most appendage of the male genitalia, which is usually quite hairy
  , and are separated but connected by a long, slender bridge (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.).

May be confused with

Anthidium can be difficult to differentiate from other Anthidiini genera, especially those that Michener (2007) places in Series B. Anthidium can be distinguished by the combination of characters above.

Known invasives

Anthidium oblongatum is native to Europe and the Middle East and was accidentally introduced to eastern Pennsylvania in 1995 (Miller et al. 2002Miller et al. 2002:
Miller, S.R., R. Gaebel, R.J. Mitchell, and M. Arduser. 2002. Occurrence of two species of old world bees, Anthidium manicatum and A. oblongatum (Apoidea: Megachilidae), in Northern Ohio and Southern Michigan. The Michigan Entomology Society 35: 65ndash;69.). They have become established in eastern Pennsylvania, Maryland, New York, and New Jersey. They have since expanded to northern Illinois and southern Canada (Miller et al. 2002Miller et al. 2002:
Miller, S.R., R. Gaebel, R.J. Mitchell, and M. Arduser. 2002. Occurrence of two species of old world bees, Anthidium manicatum and A. oblongatum (Apoidea: Megachilidae), in Northern Ohio and Southern Michigan. The Michigan Entomology Society 35: 65ndash;69.; 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.).

Anthidium manicatum, the European wool carder bee, is native to Europe. Males are well known for their highly aggressive territorial behavior (Miller et al. 2002Miller et al. 2002:
Miller, S.R., R. Gaebel, R.J. Mitchell, and M. Arduser. 2002. Occurrence of two species of old world bees, Anthidium manicatum and A. oblongatum (Apoidea: Megachilidae), in Northern Ohio and Southern Michigan. The Michigan Entomology Society 35: 65ndash;69.). In the early 1960s, they were accidentally introduced to eastern North America, specifically New York (Miller et al. 2002Miller et al. 2002:
Miller, S.R., R. Gaebel, R.J. Mitchell, and M. Arduser. 2002. Occurrence of two species of old world bees, Anthidium manicatum and A. oblongatum (Apoidea: Megachilidae), in Northern Ohio and Southern Michigan. The Michigan Entomology Society 35: 65ndash;69.; 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.). They have since spread rapidly across the U.S. and are commonly found in most states in the late summer. Anthidium manicatum has also been introduced in Canada, Brazil, Argentina, Uruguay, New Zealand, and the Canary Islands (Miller et al. 2002Miller et al. 2002:
Miller, S.R., R. Gaebel, R.J. Mitchell, and M. Arduser. 2002. Occurrence of two species of old world bees, Anthidium manicatum and A. oblongatum (Apoidea: Megachilidae), in Northern Ohio and Southern Michigan. The Michigan Entomology Society 35: 65ndash;69.).

Host associations

Plant host preferences vary widely among species of Anthidium. A few species are generalists and visit a variety of plants. Others prefer specific plant families, such as Hydrophyllaceae, Fabaceae, and Asteraceae. Researchers have found that a few species may specialize on plants such as Astragalus and Phacelia (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 addition, Anthidium collect trichomes from pubescent plants, such as Asteraceae and Lamiaceae, and use them for nesting material (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.).

Nesting behavior

All species of Anthidium are solitary. Most Anthidium make nests in pre-existing cavities in soils, walls, wood, and stems, but they have also been observed inhabiting abandoned beetle, wasp, and bee burrows (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). Nests are lined with trichomes shaved from pubescent plants, such as those from the genera Artemisia, Cirsium, and Pseudognaphalium (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.). Trichomes are also used to create the walls between nest cells. Once the nest is constructed, food is provided, and eggs are laid in the cells. Male eggs are laid at the back of the nest, unlike most other male bees that develop at the front of the nest. Due to the larger size of Anthidium males, they are likely laid at the back of the nest to allow them more time to develop (Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). Materials, such as trichomes, pebbles, wood, plant matter, and lizard feces are then used to pack the upper portion of the cavity, above the cells, to create nest plugs (Krombein 1967Krombein 1967:
Krombein, K.V. 1967. Trap nesting wasp and bees: life histories, nests, and associates. Washington, DC: Smithsonian Press.). The chosen materials are species-dependent.

Anthidium palliventre and A. rodecki only inhabit sand dunes and will dig their own nests. Females have a collection of long hairs on their foretibia, which allows them to dig in the sand. Similar to other species of Anthidium, nests are lined with trichomes.

Males often exhibit territorial behaviors over host plant patches, which secures their food source and impacts their mating success (Alcock et al. 1977Alcock et al. 1977:
Alcock J., G.C. Eickwort, and K.R. Eickwort. 1977. The reproductive behavior of Anthidium maculosum (Hymenoptera: Megachilidae) and the evolutionary significance of multiple copulations by females. Behavioral Ecology and Sociobiology 2: 385ndash;396.; Villalobos and Shelly 1991Villalobos and Shelly 1991:
Villalobos E.M. and T.E. Shelly. 1991. Correlates of male mating success in two species of Anthidium bees (Hymenoptera: Megachilidae). Behavioral Ecology and Sociobiology 29: 47ndash;53.). Larger male Anthidium have been observed to be more successful at defending and holding territories and mating (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.; 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

Anthidium are found on all continents except for Australia (Michener 2007Michener 2007:
Michener, C.D. 2007. The Bees of the World (2nd ed.). Johns Hopkins University Press, Baltimore and London, 953 pp.). They are uncommon in areas such as sub-Saharan Africa, Madagascar, and the tropics in southern Asia and Indonesia. Anthidium occurs within most of the Western Hemisphere (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.). They have specific habitat preferences, with most of the species within the U.S. preferring dry, desert habitats along the west coast (Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). Two species (A. palliventre and A. rodecki) are found only on sand dunes in the western U.S. (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.; Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.). Only four species are known to reside in northeastern North America (A. psoraleae, A. maculifrons, A. oblongatum, and A. manicatum), with the latter two being recently introduced (Miller et al. 2002Miller et al. 2002:
Miller, S.R., R. Gaebel, R.J. Mitchell, and M. Arduser. 2002. Occurrence of two species of old world bees, Anthidium manicatum and A. oblongatum (Apoidea: Megachilidae), in Northern Ohio and Southern Michigan. The Michigan Entomology Society 35: 65ndash;69.; Wilson and Carril 2016Wilson and Carril 2016:
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North Americarsquo;s Bees. Princeton University Press, Princeton and Oxford, 288 pp.).

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References

Alcock J., G.C. Eickwort, and K.R. Eickwort. 1977. The reproductive behavior of Anthidium maculosum (Hymenoptera: Megachilidae) and the evolutionary significance of multiple copulations by females. Behavioral Ecology and Sociobiology 2: 385-396.
 
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: 221-425.
 
Krombein, K.V. 1967. Trap nesting wasp and bees: life histories, nests and associates. Washington, DC: Smithsonian Press.
 
Michener, C.D. 2007. The Bees of the World. 2nd ed. Johns Hopkins University Press, Baltimore and London, 953 pp.
 
Miller, S.R., R. Gaebel, R.J. Mitchell, and M. Arduser. 2002. Occurrence of two species of old worldOld World:
the part of the world that was known before the discovery of the Americas, comprised of Europe, Asia, and Africa; the Eastern Hemisphere
bees, Anthidium manicatum and A. oblongatum(Apoidea: Megachilidae), in Northern Ohio and Southern Michigan. The Michigan Entomology Society 35: 65- 69.
 
Villalobos E.M. and T.E. Shelly. 1991. Correlates of male mating success in two species of Anthidium bees (Hymenoptera: Megachilidae). Behavioral Ecology and Sociobiology 29: 47-53.
 
Wilson, J.S. and O.M. Carril. 2016. The Bees in Your Backyard: A Guide to North America’s Bees. Princeton University Press.