Pseudoanthidium nanum

Taxonomy

Family: Megachilidae
Subfamily: Megachilinae
Tribe: Anthidiini
Genus: Pseudoanthidium, Friese 1898
Subgenus: Pseudoanthidium, Friese 1898
Species: Pseudoanthidium nanum, Mocsáry 1881

Background

Pseudoanthidium nanum are relatively small, 6–9 mm bees. They have a predominantly black integumentintegument:
a tough, protective outer layer
with symmetrical yellow spots on their face, tergaterga:
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
, and often the scutellumscutellum:
shield shaped plate behind scutum
. Their legs are predominantly yellow to orange and may be black at the base. The size of the yellow portions varies within the species. Males tend to have yellow mandibles and a larger yellow portion of their face. Females tend to have black mandibles and smaller yellow portions of their face. Both male and female specimens have a thin coat of white pubescencepubescence:
short, fine hair
that covers most of their bodies. Their wings are translucent and sometimes slightly brown.

Distribution

Pseudoanthidium nanum is native to Europe (excluding Scandinavia and the British Isles), the northern Middle East, and Central Asia (Litman et al. 2021Litman et al. 2021:
Litman, J. R., Fateryga, A. V., Griswold, T. L., Aubert, M., Proshchalykin, M. Y., Le Divelec, R., Burrows, S. & Praz, C. J. 2022. Paraphyly and low levels of genetic divergence in morphologically distinct taxa: revision of the Pseudoanthidium scapulare complex of carder bees (Apoidea: Megachilidae: Anthidiini). Zoological Journal of the Linnean Society, 195(4): 1287-1337.). Pseudoanthidium nanum is invasive to the northeastern United States (Massachusetts, New York, and New Jersey) and has been found as far west as Minnesota (Portman et al. 2019Portman et al. 2019:
Portman, Z.M., Burrows, S.J., Griswold, T., Arduser M., Irber A.J., Tonietto R.K., and Cariveau D.P. 2019. First Records of the Adventive Pseudoanthidium nanum (Mocsáry) (Hymenoptera: Megachilidae) in Illinois and Minnesota, with Notes on its Identification and Taxonomy. The Great Lakes Entomologist, vol 52 (1)). It is suspected to also be in nearby states (Moisset et al. 2021Moisset et al. 2021:
Moisset B., J. Ascher, H.G., and PaleoJon. 2021. Species Pseudoanthidium nanum. BugGuide. https://bugguide.net/node/view/580315).

 

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

Host associations

Pseudoanthidium nanum seems to prefer plants in the Asteraceae family and has been found visiting a number of genera in that family including: Arcticum, Centaurea, Cirsium, Grindelia, Helianthus, Inula, and Onopordum (Litman et al. 2021Litman et al. 2021:
Litman, J. R., Fateryga, A. V., Griswold, T. L., Aubert, M., Proshchalykin, M. Y., Le Divelec, R., Burrows, S. & Praz, C. J. 2022. Paraphyly and low levels of genetic divergence in morphologically distinct taxa: revision of the Pseudoanthidium scapulare complex of carder bees (Apoidea: Megachilidae: Anthidiini). Zoological Journal of the Linnean Society, 195(4): 1287-1337.). It has also been reported visiting the Fabaceae species Lotus corniculatus (Litman et al. 2021Litman et al. 2021:
Litman, J. R., Fateryga, A. V., Griswold, T. L., Aubert, M., Proshchalykin, M. Y., Le Divelec, R., Burrows, S. & Praz, C. J. 2022. Paraphyly and low levels of genetic divergence in morphologically distinct taxa: revision of the Pseudoanthidium scapulare complex of carder bees (Apoidea: Megachilidae: Anthidiini). Zoological Journal of the Linnean Society, 195(4): 1287-1337.).

Diagnostic characteristics

(Modified from Litman et al. 2021Litman et al. 2021:
Litman, J. R., Fateryga, A. V., Griswold, T. L., Aubert, M., Proshchalykin, M. Y., Le Divelec, R., Burrows, S. & Praz, C. J. 2022. Paraphyly and low levels of genetic divergence in morphologically distinct taxa: revision of the Pseudoanthidium scapulare complex of carder bees (Apoidea: Megachilidae: Anthidiini). Zoological Journal of the Linnean Society, 195(4): 1287-1337.)

• Female T1–T2 punctationpunctation:
  overall pattern of the punctures on a surface of a bee, includes size of punctures and the distance between them
  fine and somewhat dense with shiny interspaces.

• Male gonostylusgonostylus:
  the apical-most appendage of the male genitalia, which is usually quite hairy
  parallel-sided, only slightly wider at base. Notch at the apexapex:
  end of any structure
  approximately as deep as wide.

• Male S3S3:
  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
  premarginal brush with strongly hooked hairs at the tips.

• Male S3S3:
  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 a chevron-shaped, shiny, hairless zone that extends as a carinacarina:
  a clearly defined ridge or keel, not necessarily high or acute; usually appears on bees as simply a raised line
  along the midline of the sternum.

• Male laterallateral:
  relating, pertaining, or attached to the side
  combs on S5S5:
  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
  small, with the apexapex:
  end of any structure
  wider than the arm proceeding it. 

• Male third trochantertrochanter:
  segment of the insect leg between the coxa and the femur
  hairs short and of even length but not velvety.

May be confused with

Pseudoanthidium nanum males are most similar to P. palestinicum and kaspareki. They can be separated by the smaller laterallateral:
relating, pertaining, or attached to the side
combs on S5S5:
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
. Females are most similar to P. scapulare and P. stigmaticorne and can be difficult to separate but they tend to have overall shinier interspaces between the punctures on their tergaterga:
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
.

Nesting behavior

Little is known about the nesting biology of Pseudoanthidium nanum but most species of Pseudoanthidium nest in pre-existing cavities like in wood, stems, galls or crevices (Litman et al. 2021Litman et al. 2021:
Litman, J. R., Fateryga, A. V., Griswold, T. L., Aubert, M., Proshchalykin, M. Y., Le Divelec, R., Burrows, S. & Praz, C. J. 2022. Paraphyly and low levels of genetic divergence in morphologically distinct taxa: revision of the Pseudoanthidium scapulare complex of carder bees (Apoidea: Megachilidae: Anthidiini). Zoological Journal of the Linnean Society, 195(4): 1287-1337.).

Known invasives

Pseudoanthidium nanum has been identified in the northeastern United States and has been found as far west as Minnesota (Portman et al. 2019Portman et al. 2019:
Portman, Z.M., Burrows, S.J., Griswold, T., Arduser M., Irber A.J., Tonietto R.K., and Cariveau D.P. 2019. First Records of the Adventive Pseudoanthidium nanum (Mocsáry) (Hymenoptera: Megachilidae) in Illinois and Minnesota, with Notes on its Identification and Taxonomy. The Great Lakes Entomologist, vol 52 (1)).