SHARP-EATMAN
NATURE
PHOTOGRAPHY
ID GUIDE TO WILD BEES
OF THE NATIONAL BUTTERFLY CENTER
Mission, Texas
WOOL-CARDER BEES
Anthidium
Above Photo Copyright 2025 Dan Jones
WOOL CARDER BEES
Tribe Anthidiini - Genus Anthidium
On March 13, 2025, master photographer Dan Jones found and photographed a curious bee at the National Butterfly Center -- the spotted wool carder (Anthidium maculosum), which had not been seen in Hidalgo County since 1946.
On March 16, Jones returned to the NBC to photograph more wool carder bees. He pointed out the Anthidium to biologist John Brush, and both documented the bees' appearance with photographs Jones also ran into Heather Holm, Minnesota author of several books on bees, who was visiting the NBC that day. She joined him in photographing the Anthidium.
On the same day, biologist Ernesto Herrera spotted and photographed the same unusual wool carder bee species in his backyard garden in Mission, Texas.
A few days later, on March 22, John Brush found more Anthidium maculosum at Quinta Mazatlan of McAllen, Texas, where he works as an urban ecologist. The next day, he encountered wool carder bees in a third Hidalgo County town -- at the Municipal Park Garden of Edinburg.
All three men and Heather Holm recorded their finds on i-Naturalist. Their photographs are shown here.
Entertaining Anthidium behavior
Male Anthidium often attract attention in a garden because of their entertaining territorial behavior. They patrol their small territories (often no larger than a single plant), defending them zealously by charging and butting away other insects that come too close. In March, 2025, Ernesto Herrera noticed Anthidium maculosum males fighting off other insects in his back yard -- including large red Pollstes wasps -- to prevent them from approaching a hedgenettle.
Most Anthidium are solitary bees that nest in pre-existing cavities found in the ground, wood, stems, and other plant matter. Wool carder bees acquire their name from the behavior of female Anthidium. Females “card” fibers (called trichomes) from plants, shaping them into cottony balls which they transport to their nests.
Anthidium females pack the upper portions of their nest burrows with trichomes, pebbles, wood particles, and chewed-up plants. They also use trichomes to line the inner walls of their nest tunnels, and to line and plug their egg chambers. The bees' brood cells resemble small cotton balls aligned in short rows.
The mandibles of Anthidium females possess multiple teeth that allow them to scrape and gather plant fibers. Female Anthidium of various species -- including the A. maculosum shown here -- also have hooked or curved facial hairs that facilitate pollen collection from flora such as mints and pea-family flowers. In addition, the females’ lower legs (basitarsi) are hairy, a feature that allows the bees to absorb plant secretions used in nest construction and waterproofing.
Distinguishing traits of the genus Anthidium
Bees of the genus Anthidium are medium-large, burly insects. In North America, they are usually black or brown with symmetrically-arranged yellow or pale markings on the face, thorax and abdomen. Females carry pollen on the sternum (underside of the abdomen), a general attribute of the family Megachilidae.
Traits that aid in distinguishing North American Anthidium from other bee genera include the following. (1) The bees’ heads, bodies and legs are often covered with conspicuous, long, pale hairs. (2) Anthidium lack pad-like structures on their feet known as arolia -- this helps differentiate them from other genera of the bee tribe Anthidini, which usually have arolia. (3) Anthidium faces are distinctive because the subantennal sutures (seams under the compound eyes) are usually straight, a trait that helps distinguish them from Anthidiellum.
Geographical range
Anthidium is one of the most diverse genera of the family Megachilidae. Anthidium are found in both the Old World and New World, comprising more than 160 species worldwide, and more than 90 in the Western Hemisphere alone. Of these, 42 occur in North America; within the United States, most Anthidium species are found west of the Mississippi. Anthidium are particularly abundant in arid areas.
Anthidium maculosum is found throughout the western United States and much of Mexico, as far west as California and Nayarit, as far north as North Dakota and Oregon, and as far south as Honduras. Before 2025, however, Anthidium maculosum were rarely recorded in the Lower Rio Grande Valley.
According to records from the American Museum of Natural History, and from the Discover Life Bee Species and World Checklist, the last sightings of Anthidium maculosum near the South Texas / Mexico border are decades old. The most recent regional Anthidium maculosum records include specimens found in Val Verde County (1966); Brewster Co. (1963, 1966); Culberson County (1963); Uvalde Co. (1963); Jeff Davis Co. (1947); and Hidalgo Co. (Pharr) in (1946); and in the Mexican border states of Nuevo Leon (1991) and Coahuila (1990).
Three other Anthidium species are known to inhabit areas close to the South Texas / Mexican border. These include: Anthidium cockerelli, found in Dimmit County (1949): Anthidium rodriquezi found in Tamaulipas (date unavailable); and Anthidium palmarum, found in Uvalde County (1952,) and Jeff Davis County (1954).
Anthidium maculosum and associated flora
Spotted wool carder bees gather pollen and nectar from a range of plants. They are often associated with pea family flowers and mints. In addition to visiting flowers for food, female Anthidium maculosum visit aster-family flora and other plants to collect trichomes and floral oils.
The bees shown here were found feeding principally on mint-family flora such as shrubby blue salvia (Salvia ballotiflora) and hedgenettle (Stachys drummondii), and on the pea-family plant Texas babybonnnets (Corsetia axillaris). Other plants visited for pollen and nectar included boneset (Tamaulipa azurea) and brushland lantana (Lantana achyranthifolia).
The female Anthidium maculosum were also observed and photographed carding fibers from the leaves of cudweed (Gamochaeta) and prickly poppy (Argemone).
TAXONOMY OF WOOL CARDER BEES
Order: Hymenoptera
Family: Megachilidae
Subfamily: Megachilinae
Tribe: Anthidiini
Genus: Anthidium
Species shown on this page:
Anthidium (Anthidium) maculosum
A male Anthidium maculosum
Photo copyright 2025 Dan Jones
Mating Anthidium maculosum
Copyright 2025 Ernesto Hererra
A female Anthidium masculosum gathering fibers from cudweed
Copyright 2025 John Brush
A female spotted wool carder bee
Copyright 2025 Heather Holm
Alcock, J., Eickwort, G.C., and Eickwort, K.R. (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.
Danforth, B. N., Minckley, R. L., & Neff, J. L. (2019). The Solitary Bees: Biology, Evolution, Conservation. Princeton University Press.
Gonzalez, V.H. and Griswold. T.L. (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 Linnaean Society 168: 221-425.
Grigarick A.A., & Stange, L.A. (1968). The Pollen Collecting Bees of the Anthidiini of California (Hymenoptera: Megachilidae) Bulletin of the California Insect Survey,Volume 9.
Krombein KV. (1967). Trap nesting wasp and bees: life histories, nests and associates. Washington, DC: Smithsonian Press, iii–ivi.+570 pp. Kurtak BH. 1973.
Family: Megachilidae
Size: Females 8.5-11.5 mm
Males 9.2-13.1 mm
Associated plants:
Shrubby blue salvia
Hedgenettle
(Stachys drummondii)
Plant family: Lamiaceae
Texas babybonnets
Plant family: Fabaceae
Blue boneset
(Tamaulipa azurea)
Plant family: Asteraceae
Brushland lantana
(Lantana achyranthifolia)
Plant family: Verbenaceae
Plants visited for fibers:
Cudweed
(Gamochaeta)
Plant family: Asteraceae
Prickly poppy
(Argemone)
Plant family: Papaveraceae
Spotted wool carder bee
Anthidium maculosum
Wool carder bees of North America tend to have dark bodies with yellow or pale markings. Their heads and bodies are covered with pale hairs. (Photo by Dan Jones)
The pale-yellow patterns on carder bees' bodies can aid in distinguishing species. This species (Anthidium oblongatum), found outside of the Valley, has elongated interrupted stripes on its abdomen.
By contrast, the spotted wool carder bee, Anthidium maculosum, found in the Valley, has four pale symmetrical markings on each of the first five segments of its abdomen. (Photo by Dan Jones)
A mating female (above) and male (below): spotted wool carder bees may couple multiple times with several different mates. (Photo by Ernesto Herrera)
A male spotted wool carder bee feeding on Texas babybonnets (Photo Dan Jones)
A female spotted wool carder bee scraping Texas babybonnet blossoms with its mandibles. (Photo Dan Jones)
A female Anthidium maculosum: note the two yellow spots on the female bee's lower face. (Photo Heather Holm)
A female spotted wool carder bee scraping fibers from a prickly poppy leaf (Photo Heather Holm)
A female gathering fibers from cudweed: female Anthidium tend to card trichomes from plants with woolly leaves. (Photo John Brush)
A male Anthidium maculosum drinking nectar from brushland lantana. Note the male bee's largely yellow face. (Photo John Brush)
A male Anthidium maculosum on Salvia ballotiflora
Copyright 2025 Dan Jones
TRAITS OF SPOTTED WOOL CARDER BEES
Anthidium maculosum have darkly-colored heads and bodies covered with pale-yellow spots. "Maculosum" means "spotted" in Latin. Both males and females have a "fuzzy" appearance resulting from long white hairs that cover their heads, bodies and legs.
The pale markings on female and male Anthidium maculosum are similar and appear as follows: there are two symmetrical pale-yellow spots right above the bees' compound eyes; pale spots in front of and behind the tegulae (wing nodes); and two roughly triangular pale markings on the scutellum (2nd thorax segment).
On the bees’ abdomens, the yellow markings are arranged as follows: on each of the first five segments ( T1-T5) is a row of four distinct markings (two triangular spots in the center, flanked by two roughly rectangular spots laterally). The sixth tergal segment (T6) is usually black on females. On males, there are two spots shaped like rounded triangles on T6. Other notable traits specific to females vs. males are noted below.
Females: The lower face of the female Anthidium maculosum has two roughly triangular yellow markings. The female's mandibles have 6-8 teeth (usually seven), and are black with some yellow markings on the outer surfaces. The third segments of the female's antennae (F1) are elongated.
The basitarsi (lower segments) of the female's front and middle legs are pale yellow. The tibia (above the basitarsi) are predominantly black with yellow spots on the outer surfaces near the base.
The scopal hairs on the underside of the female's abdomen (the sternum) are white. Most of the hairs elsewhere on the bee’s head and abdomen are also white, although there are some brown hairs on the face, vertex, inner basitarsi and the upper abdomen. Females’ basitarsi (lower legs) are covered with especially dense, long pale hairs.
According to Gonzalez & Griswold (2013), these minute traits distinguish female Anthidium maculosum from most other North American Anthidium species: (1) Females have distinctive ridges on each hind-leg tibia; and (2) the frons ("forehead) of the female is dull with coarse, sparse pits. An additional notable trait is that the bottom (distil) edge of the female's clypeus (the face part above the mandibles) lacks teeth, tubercules or other projections.
Males: On males, a much larger portion of the face is pale yellow. Most of the clypeus is yellow; two triangular yellow marks also flank the clypeus, extending upward nearly to the antennae; and most of the outer mandibles are yellow. The male has 3-toothed mandibles, and its antennal scapes are entirely black.
On males, T7 (on the tip of the abdomen) is black, and its rear edge is three-pronged, with curved indentations between the prongs, and with the outer prongs longer than the center prong.
The males' legs appear largely pale to the naked eye: viewed minutely, the outer surfaces of the middle and hind basitarsi (lower legs), and outer surface of the lower middle tibiae (above the basitarsi) are ivory or light yellow.
Size of males vs. females: Anthidium maculosum females construct their nest tunnels as a sequence of egg chambers. Krombein (1967) observed that the rearmost, and hence oldest, cells of Anthidium maculosum tunnels are reserved for male offspring. As a result, males have longer to develop and emerge larger than females. This is somewhat unusual, because in most bee genera, females are larger than males.
Similar Anthidium of South Texas and Tamaulipas: Anthidium maculosum can be differentiated fairly easily from the three other regional Anthidium species mentioned above. The abdomens of the male and female Anthidium rodiguezi are almost entirely black, without yellow spots on the terga. The female's face is black; it lacks the two yellow spots on its lower half characteristic of A. maculosum. On Anthidium palmarum, the yellow areas on each of abdominal segments T1-T5 form two irregular yellow shapes rather than four distinct spots. There are two rounded tubercules on the bottom (distil) edge of the female's clypeus. On Anthidium cockerelli, the spots on T1-T5 lack a distinct triangular or rectangular shape and have irregular edges. On the male, T7 is mostly yellow rather than black, and the inner and outer spots on either side of T3-T5 are joined by a thin line. The female Anthidium cockerelli lacks the two yellow spots on its lower face, and there are two tooth-like projections on the distil edge of its clypeus. Close-up photographs showing detailed characteristics of these species are available at the website Exotic Bee ID: Anthidium cockerelli. Anthidium palmarum. Anthidium rodriiguezi. Anthidium maculosum.
Anthidium Species of the Lower Rio Grand Valley
CITE THIS PAGE: Sharp, Paula and Ross Eatman. "Anthidium." Wild Bees of the National Butterfly Center of Mission, Texas. 15 Jan. 2019-2025, http://www.wildbeestexas.com. Accessed [day/month/year guide accessed].