top of page

Mission, Texas

Ashmeadiella maxima


Tribe Osm
iini - Genus Ashmeadiella

Ashmeadiella belong to the tribe Osmiini of the family Megachilidae -- like the Heriades resin bees and Osmia mason bees of this guide's previous sections.  

Bees of the genus Ashmeadiella are found only in North America and Central America.  Within the United States, Ashmeadiella occur principally in western desert and semi-arid areas.  Two species are native to the Valley:  both are found in dry habitats where cactus and other xeric plants abound. 

Distinguishing traits of Ashmeadiella


Ashmeadiella are small to medium-small bees with robust builds; nonmetallic, usually black heads and bodies; and abdomens banded with pale hairs.  Some species have red or partly-red abdomens.  As with other members of the family Megachilidae, the forewings of Ashmeadiella have two submarginal cells, and females transport pollen on scopal hairs located under the sternum (the underside of hte abdomen).  The tarsal claws of  Ashmeadiella possess arolia.  The front surface of the first segment of an Ashmeadiella abdomen is widely concave and bounded with a ridge.

Ashmeadiella can be separated from similar bee genera by the following two traits.  (1) The tip of the male Ashmeadiella’s abdomen (T6) usually has four prongs.  (2) On both males and females, the mesepisternum (the middle segment of the side of the thorax) is divided by a weak ridge:  the area in front of the ridge is smooth and shiny, and the area behind it is pitted.  The second of these traits requires strong magnification to isolate, and it may be obscured under hairs.  The distinctive four-pronged abdomen of the male bee, however, is readily recognizable, even to the naked eye, and is the best means of diagnosing the genus in the field.  


Ashmeadiella are sometimes confused in the field with Heriades, but within Texas, Ashmeadiella females are generally larger and stouter; Heriades males lack the abdominal prongs; and the eyes of Ashmeadiella are a more brilliantly-colored blue or green.


All Ashmeadiella are solitary cavity nesters.  They nest in a variety of places, among them, pre-existing holes in wood, dead or decaying cactus, beetle burrows, shells or (less often) the ground.  Ashmeadiella nests usually take the form of a tunnel divided at the end into egg cells.  The cells contain one or several eggs and are separated by partitions made of chewed-up plant materials and saps. 

Ashmeadiella cactorum; Copyright 2023 Paula Sharp

A female Ashmeadiella cactorum



Order:   Hymenoptera

Family:   Megachilidae

Subfamily:   Megachilinae

Tribe:  Osmiini

Genus:  Ashmeadiella

Species shown on this page:  
    Ashmeadiella (Ashmeadiella) cactorum cactorum

    Ashmeadiella (Ashmeadiella) maxima

Ashmeadiella Species of the Lower Rio Grande Valley

Greater Ashmeadiella

Ashmeadiella (Ashmeadiella) maxima

Family:  Megachilidae

Size:  7-9 mm (females)

          8 mm  (male)      

Associated plants:
(Ziziphus obtusifolia )

Plant family: Rhamnaceae

Arkansas dozedaisy

Aphanostephus skirrhobasis

Plant family: Asteraceae

When and where seen:

May 11, 2021

Pixie Preserve (Hidalgo Co.)

May 1, 2023

Dos Venadas Ranch

Rio Grande City TX  (Starr Co.)

Ashmeadiella maxima; Photo Copyright 2023 Paula Sharp

A male Ashmeadiella maxima

Ashmeadiella maxima; Copyright 2023 Sharp-Eatman Nature Photography

The tip of the abdomen of a male Ashmeadiella maxima

Ashmeadiella maxima; Copyright 2023 Paula Sharp

A female Ashmeadiella maxima

Ashmeadiella maxima is a black bee with a robust build and an abdomen banded by pale hairs.   As its name implies, Ashmeadiella maxima is large for its genus -- its size helps to identify it in the field. 


Male Ashmeadiella species are separated in part by the characteristics of the prongs on the bees’ abdomens, and by the positioning of the ocelli on the vertex.   The male Ashmeadiella maxima also  can be recognized by its black tarsi, and the dense white hairs on its face.   The female Ashmeadiella maxima can be recognized by its size and its braod head.


Within the United States, Ashmeadiella maxima is found principally along southern border areas of Arizona, New Mexico and Texas.  This species appears in mid- through late spring in the Valley.

Cactus Ashmeadiella

Ashmeadiella (Ashmeadiella) cactorum)

Family:  Megachilidae

Size:  6-8 mm (female) 

          6 mm (male)


Associated plants:

Arkansas dozedaisy

(Aphanostephus skirrhobasis)

Plant family:  Asteraceae


Herissantia crispa)

Plant family:  Malvaceae

Texas palo verde
(Parkinsonia texana)

Plant family:  Fabaceae  

When and where seen:

May 9, 2021,  June 20, 2021

El Mesteno Ranch

Puerto Rico (Hidalgo Co.)

Rio Grande City (Starr Co.)

Ashmeadiella cactorum cactorum; native bee; Copyright 2023 Sharp-Eatman Nature Photography

A female Ashmeadiella cactorum

Ashmeadiella cactorum is a moderately small, black bee with a coarsely-punctured body; an abdomen striped by pale hair bands on T1-T5; a thorax and face sparsely covered with white hairs; and (on females) pale-blue eyes.  The bee’s tegulae are black and its wings are glassy brown with dark brown veins.  Females have yellowish-white scopal hairs under their abdomens.  Ashmeadiella cactorum is smaller than the Ashmeadiella maxima shown above, and less densely haired, and lacks its broad face. 


Ashmeadiella cactorum is found in the southwestern and western United States, and throughout Mexico.  It occurs in both Starr and Hidalgo Counties.  Despite its name, Ashmeadiella cactorum is not a cactus specialist. It is a generalist pollinator that visits plants from a broad range of families.

CITE THIS PAGE:  Sharp, Paula and Ross Eatman.  "Ashmeadiella."  Wild Bees of the National Butterfly Center of Mission, Texas. 15 Jan. 2019,  Accessed [day/month/year guide accessed].

bottom of page