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Mission, Texas

Dieunomia nevadensis bakeri; Copyright 2021 Paula Sharp

Nomia & Dieunomia


Nomia & Dieunomia

Nomia and Dieunomia are two genera of ground-nesting bees that belong to the subfamily Nomiinae, within the  sweat bee family Halictidae.  Sometimes called "large sweat bees,"  Nomia and Dieunomia tend to run bigger than the Augochlorini and Halictini sweat bees shown in the preceding sections of this guide. 


Nomia inhabit North America, Africa, Australia and Asia.  Nomia of North America are dark-bodied, with abdomens that are relatively hairless and often girded by striking pearlescent  bands.  Males often have enlarged tibiae, used to subdue females during mating.

The faces of Nomia are distinctive:  they are somewhat round and a little eerie, with eyes that converge downward, seeming to join seamlessly with the lower face.  The typical Texan Nomia is a medium-sized bee, i. e., around the size of a honey bee or slightly smaller.

​Species Identification of Nomia

North American Nomia species are differentiated by such traits as the presence and completeness of iridescent bands on the bees' abdomens; the absence or presence of such bands on the first abdominal segment in particular; the pitting on the bees' faces, thoraxes and abdominal segments; and (in males) the color of the bees' antennae. 


Males are often identified in part by leg traits.  Males' legs differ in the degree to which their hind-leg tibiae are enlarged, and by their color.  The hind-leg tibiae of male Nomia tetrazonata, for example, have pale-gold areas that expand above the leg spurs in a roughly triangular shape, as shown in the photographs below.  One Texas species, Nomia nortoni, has grossly dilated tibiae clearly visible to the naked eye.



Dieunomia are found only in the New World.  They range greatly in size, from as large as 23 mm, to as small as 7 mm. There are at least nine species of Dieunomia in the Americas, and these divide into two subgenera, differentiated roughly by size:  larger bees fall into the subgenus Dieunomia, and smaller ones into Epinomia. The Baker's dieunomia shown on this page is a member of the subgenus Epinomia. 


Dieunomia are solitary bees, with each female building its own individual nest.  Nonetheless, Dieunomia sometimes nest in large aggregations in sandy soil or farmland.  Because their nests are deep, they can survive plowing.  Dieunomia are pollen specialists of the plant family Asteraceae.


Distinguishing traits of Dieunomia


In The Bees of the World, Charles D. Michener noted these two distinctive traits of Dieunomia:  the first segment of the Dieunomia’s abdomen is V-shaped, and it has a concave depression in the middle.  Michener also wrote that Dieunomia can be distinguished from Nomia by the fact that Dieunomia have bands of hair on the second through fourth segments of their abdomens, while on Nomia those segments are relatively hairless and have an enamel-like appearance.  In addition, on Dieunomia, the same segments tend to have some kind of pitting, while on Nomia, the segments usually lack pits. 

Female Dieunomia, in addition to scopal hairs on their hind-leg tibiae, have long scopal hairs under their abdomens (on the second through fifth sternal segments), often clearly visible from the sides as well as from below.  Male Dieunomia often have enlarged hind legs; their middle legs may be partly enlarged as well.  The faces of Dieunomia are generally similar to those of Nomia -  somewhat round, with convergent eyes.

Nomia tetrazonata; Copyright 2021 Paula Sharp

A male four-banded Nomia on Berlandier's fiddlewood 



Order:   Hymenoptera

Family:   Halictidae

Subfamily:   Nomiinae

Tribe:  Nomiini

Genus:   Nomia

Subgenus:  Acunomia
Species found at NBC:
    Nomia tetrazonata uvaldensis


Order:   Hymenoptera

Family:   Halictidae

Subfamily:   Nomiinae

Tribe:  Nomiini

Genus:   Dieuomia

Subgenus: Epinomia
Species found at NBC:
    Dieunomia nevadensis bakeri

Four-banded Nomia Bee
aka Pearly-banded Bee

Nomia tetrazonata uvaldensis


Family:  Halictidae

Size:  9 mm - 10 mm (males and females)

Associated flora:  

Berlandier's fiddlewood
(Citharexylum berlandieri)

Plant family:   Verbenaceae


(Condalia hookeri)



(Karwinskia humboldtiana)


(Eysenhardtia texana)


(Zizyphus obtusifolia)

Texas hogplum

(Colubrina texensis)

Family:  Rhamnaceae


(Guaiacum angustifolium)

Family:  Zygophyllaceae


(Leucophyllum frutescens)

Family:  Scrophulariaceae


(Sideroxylon celastrinum)

Family:  Sapotaceae

When and where seen:  

NBC:  March - May 201

Puerto Rico, TX:  May, 2021

Rio Grande City, TX:  June, 2021

La Puerta Land Tract:  May 2021

Falcon State Park:  April 2023

Nomia tetrazonata; Copyright 2023 Paula Sharp

A male four-banded nomia (Nomia tetrazonata)

Nomia tetrazonata; Copyright 2023 Paula Sharp

A female four-banded nomia


Male four-banded nomia on Kidneywood

Also known as the pearly-banded bee, the four-banded Nomia (Nomia tetrazonata) is a medium-sized black bee with an abdomen striped by opalescent bands that shimmer blue or yellow-orange in sunlight.  Female bees have three pearlescent bands on the abdomen and males four.  The lower hind legs of males are enlarged and partly yellowish-brown.


In the Lower Rio Grande Valley, male Nomia tetrazonata uvaldensis appear in April.  They often emerge in large groups all at once.  This website's authors have encountered April aggregations of male Nomia tetrazonata,  numbering in the hundreds, on small-flowered shrubs such as Berlandier's fiddlewood, coma, coyotillo, guayacan,  kidneywood,  lotebush and Texas hogplum.


Bee Behavior:  Entomologist William T. Wcislo has authored and co-authored several studies of this species.  According to Wcislo, four-banded nomia males sleep on vegetation near areas where females are nesting; during waking hours, males patrol nesting sites, waiting to pounce on females as they emerge from their ground holes.  As shown in the accompanying photographs, males of this species have enlarged leg segments fringed with long hairs, attributes used to subdue females during mating.

All known North American Nomia bees nest in soil, usually in flat ground.  Nomia females coat the linings of their egg cells with a waterproof wax-like material. The burrow entrances of some Nomia species are marked with a “tumulus” or turret.  

Many Nomia species are solitary.  Nomia tetrazonata, however, are known to live communally, with up to 20  bees sharing a single nest.  Four-banded nomia nests lack tumuli and turrets at their entrances, but may be impressively deep, running as far beneath the soil as 20 inches (50 cm).  The nests of four-banded nomia are sometimes invaded by the cuckoo bee species Triepeolus verbesinae.

Nomia & Dieunomia Species of the National Butterfly Center

Dieunomia nevadensis bakeri is a small, black bee with red legs and tegulae, a dark abdomen banded by pale hairs, and smoky wings that darken toward the outer edges  The thoraxes of both females and males are covered with pale hairs, and the bees have a generally hairy appearance.

Dieunomia nevadensis bakeri can be differentiated from similar Dieunomia species in part by size – Baker’s dieunomia are small even for bees of the subgenus Epinomia.  The hind tibiae of Baker’s dieunomia are also distinctive.  The male’s hind tibiae each have a bump in the middle and a spike on the lower end.


Dieunomia nevadensis bakeri ranges eastward from Texas to Florida and North Carolina, westward as far as Colorado and Wyoming, and northward as far as Illinois.  Cockerell and Cresson identified five subspecies of Dieunomia nevadensis, differentiated in part by geography and the colors of their abdomens.  The subspecies Dieunomia nevadensis arizonensis occurs in the southwestern and western United States and Mexico, and its range overlaps somewhat with that of Dieunomia nevadesis bakeri.  The former is easily distinguished by its extensively red abdomen.

Baker's Dieunomia

Dieunomia nevadensis bakeri

Family:  Halictidae 

Size: 9-10 mm  (female & male)

Associated flora:

Hoary black-foot daisy

(Melampodium cinereum)

Seaside goldenrod

(Solidago sempervirens)
Family: Asteraceae

Where and when seen:  

NBC: October 2019, NBC

Roma, TX: June 12, 2021

Dieunomia nevadensis bakeri; Copyright 2021 Paula Sharp

A female Baker's dieunomia (Dieunomia nevadenis bakeri)

Dieunomia nevadensis bakeri;  (c) Copyright 2019 Paula Sharp

A male Baker's dieunomia (Dieunomia nevadensis bakeri)

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

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