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Mission, Texas

Eucera wilmattae; Tetraloniella wilmattae; Copyright 2020 Paula Sharp

Tetraloniella / Eucera / Xenoglossa


​Genus Eucera or Xenoglossa

Formerly Genus Tetraloniella

Before 2018, the bees featured on this page were classified for decades as Tetraloniella, a genus coined by the American entomologist William Harris Ashmead in 1899. 

In 2001, the entomologist Walter Laberge undertook a comprehensive study of Tetraloniella.  For this work, titled "Revision of the bees of the genus Tetraloniella in the New World,” LaBerge examined 6,504 specimens of Tetraloniella, boiling them down to 35 distinct species, which he described in painstaking detail.  Among them were Tetraloniella eriocarpi, Tetraloniela wilmattae and Tetraloniella panenalbata.  

LaBerge's description of the genus Tetraloniella is still helpful today -- it accurately characterizes all of the long-horned bees featured below.


Laberge characteried Tetraloniella as follows:  They are small to moderate-sized bees that superficially resemble long-horned bees of the genus Melissodes.  The abdomens of Tetraloniella are often banded by pale hairs. Females usually have  dense, and sometimes feathery, pollen-collecting (scopal) hairs on their hind legs.  Males have long antennae, and yellow or pale markings on the mandibles.  The male's clypeus and labrum (the mouthparts situated above and between the mandibles) are also pale or yellow. Some males have toothlike projections on either side of the sixth segment (T6) of their abdomens.

Renaming of the genus Tetraloniella

In 2018, entomologists Dorchin et al. described the classification system for Eucerini as sprawling and messy, and they recommended a rehaul. Dorchin et al. proposed, among other changes, that bees occupying the genus Tetraloniella be resituated in the genus Eucera.  New World Tetraloniella like those shown on this guide page were reclassified as Eucera (Xenoglossodes). 

Since that time, more seismic upheavals in the longhorned bee universe have followed.  Scientific nomenclature for longhorn bee genera is currently in a state of flux.  A 2023 publication by Freitas et al.  proposes the reclassification of  some Eucera (Xenoglossodes) in the resurrected genus Xenoglossa.

Recommended reading: 

Dorchin A, López-Uribe MM, Praz CJ, Griswold TL, Danforth BN. 2018. Phylogeny, new generic-level classification, and historical biogeography of the Eucera complex (Hymenoptera: Apidae). Molecular Phylogenetics and Evolution 119:81–92.

Freitas FV, Branstetter MG, Franceschini-Santos VH, Dorchin A, Wright KW, López-Uribe MM, Griswold TL, Silveira FA, Almeida EAB. 2023. UCE phylogenomics, biogeography, and classification of long-horned bees (Hymenoptera: Apidae: Eucerinae), with insights on using specimens with extremely degraded DNA. Insect Systematics and Diversity 7(4), 3: 1-21.   


Eucera fasciatella; Tetraloniella fasciatella; Copyright 2022 Paula Sharp

A male Eucera fasciatella



A female Eucera paenalbata


Order:   Hymenoptera

Family:   Apidae

Subfamily:  Eucerinae

Tribe:  Eucerini

Genus:  Eucera

Subgenus:   Xenoglossodes
Species shown below:

       Eucera (Xenoglossodes) eriocarpi Tetraloniella eriocarpi -

       Eucera (Xenoglossodes) fasciatella  Tetraloniella fasciatella

       Eucera (Xenoglossodes) paenalbata Tetraloniella paenalbata -

       Eucera (Xenoglossodes) wilmattae Tetraloniella wilmattae -

Eucera (Former Tetraloniella) Species of the Lower Rio Grande Valley

Wilmatte's Long-horned Bee

Eucera (Xenoglossodes) wilmattae

Family:  Apidae

Size:  10 mm - 2/5" 

Associated  plants at NBC: 

Skeleton-leaf goldeneye
(Viguiera stenoloba)


(Gaillardia pulchella)

Hoary blackfoot

(Melampodium cinereum)

Texas palafox

(Palafoxia texana)

Mexican hat

(Ratibida columnifera)

Tiny Tim

(Thymophylla tenuiloba)

Cowpen daisy

(Verbesina encelioides)
Plant Family: Asteraceae)

When and where seen:

NBC (Hidalgo Co.)

November 2018; April-May 2019, November 2023

Dos Venadas Ranch

Rio Grande City (Starr Co.) 

April 26, 2023

Tetraloniella wilmattae or Eucera wilmattae - (c) Copyright 2018 Paula Sharp

A male Wilmatte's long-horned bee (Eucera wilmatte)

Tetraloniella wilmatte long-horned bee - (c) Copyright 2019 Paula Sharp

A female Wilmatte's long-horned bee

This species was named after Wilmatte Porter Cockerell, who first recorded it in 1917, in an article titled "Collecting Bees in Southern Texas."  Cockerell discovered a single female specimen in Port Isabel, Texas, about 80 miles from Mission, where the National Butterfly Center is located.  Cockerell noted that the  bee was feeding on a "yellow composite"  (an aster-family flower).  

More than 100  years later, Wilmatte's long-horned bees still visit yellow composites  at the National Butterfly Center. 


Wilmatte's long-horned bees are enchanting insects. Males have bright yellow faces and exceptionally long antennae, which they curl inward at the tips like the ends of a moustache.  Female bees' heads and bodies are  are clothed in golden hair; males are covered in ivory hairs.

Both males and females have opaque black eyes that look like apple seeds.  This trait is visible to the naked eye, and helps the casual naturalist distinguish this species easily from Melissodes long-horned bees of the Lower Rio Grande Valley, which have brightly-colored (usually green or blue) eyes.

Wilmatte's long-horned bees fly from April through November in the Valley.  They are found in Cameron, Hidalgo and Starr Counties.   This species' documented population is centered in South Texas.  It ranges into Mexico, as least as far south Nuevo Leon, and has been sighted as far west as new Mexico.  In the Valley, this species visits aster-family flowers nearly exclusively.

Fasciatella long-horned bee

Eucera (Xenoglossodes) fasciatella


Family:  Apidae

Size:  10.5 mm (male) 

Associated plant:
Shrubby blue salvia

(Salivia ballotiflora)

Plant family:Laminacaea

When and where seen:

May 30, 2021
Falcon State Park
Roma (Starr County

Eucera fasciatella; Tetraloniella fasciatella; Copyright 2022 Paula Sharp

A male Eucera fasciatella

Eucera fasciatella; Tetraloniella fasciatella; Copyright 2022 Paula Sharp

A male Eucera fasciatella

The shape and color of the ivory facial markings of the male Eucera fasciatella distinguish it from all other male longhorn bees of the Lower Rio Grande Valley.


In 1970, upon discovering this species, LaBerge placed the  fasciatella long-horned bee in a new genus, which he named Pectinapis.  Some females of this genus had comb-like hairs above the clypeus; all had hairy facial depressions above the clypeus .  LaBerge  speculated that  female Pectinapis used their novel facial apparatus to rake pollen from flowers.  He noted that some anthophorine (digger) bees had similar facial hairs, which they used to gather pollen.  (The most common Valley species with such clypeal hairs is Anthophora capistrata,  which collects pollen principally from salvia.) 


Michener later reclassified Pectinapis fasciatella in Bees of the World:  he felt that the bee's unusual facial characteristics did not merit the conjuring of a new genus.  He cast this species into the same genus as Wilmatte’s long-horned bees, rechristening it Tetraloniella (Pectinapis) fasciatella.  

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

Goldenweed long-horned bee

Eucera (Xenoglossodes) eriocarpi

Family:  Apidae

Size: 7-9 mm (male and female)  

Associated plants:
Texas palafoxia

(Palafoxia texana)

Arkansas dozedaisy

(Aphanostephus skirrhobasis)

Plant family:  Asteraceae

When and where seen:

April 26, 2023

Dos Venadas Ranch
Rio Grande City, TX  (Starr Co.)

Eucera eriocarpi; Tetraloniella eriocarpi; Copyright 2023 Paula Sharp

Male Eucera eriocarpi

Male Eucera eriocarpi are covered primarily with ivory hairs; on some individuals of the species, the hairs may be pale-rust or golden.  The male bee has very long antennae, which appear red to the naked eye; underneath they are yellow or orange.  The male's clypeus and labrum are yellow. 


The male Eucera eriocarpi can be confused easily in the field with Eucera  wilmattae,  shown directly above.  On the latter, the last 3 1/2 flagellar segments of the antennae are dark; the male Eucera eriocarpi lacks this trait. 

Female Eucera eriocarpi and E. wilmatte can be separated by the following traits.   (1) On the female Eucera erocarpi, the pale hair bands on the abdomen run together; on E. wilmatte, the tergal bands are more distinct and separated.  (2) On the female E. eriocarpi, the labrum is all pale; on the female E. wlmattae, the labrum is partly or entirely black.

Eucera eriocarpi ranges throughout Mexico and much of Texas and the southwestern United States.  It is found as far west as Nevada and as far north as Kansas.

Woolly-white long-horned bee

Eucera (Xenoglossodes) paenalbata

Family:  Apidae

Size:  10.5 mm (female) 

Eucera paenalbata is a small and pretty long-horned bee, with pale-blue eyes; white and light-orange thorax hairs; golden-pink tegulae; and an abdomen clothed in pale hairs. This species’ scientific name (paen- or “almost”) is a nod to Eucera albata, a similar white-and pinkish-gold bee first described by Cresson in 1872.  


LaBerge first described the woolly-white long-horned bee in 2001, christening it Tetraloniella paenalbata. Like Eucera wilmattae shown above, Eucera paenalbata exhibits the characteristics of the former genus Tetraloniella:  the female bee’s hind-leg scopal hairs are dense and plumose.  The male Eucera paenalbata has a pale clypeus and labrum, and its mandibles are pale at the base. 

This species ranges from Colorado and Kansas through Texas and Tamaulipas, and  as far south as Mazatlán.  LaBerge recorded Eucera paenalbata feeding on purple dalea (Dalea lasiathera), a pea-family plant. The female bee found here was foraging on the composite flowers Mexican hat and cowpen daisy.  

A female woolly-white long-horned bee (Eucera paenalbata)

A female woolly-white long-horned bee

Associated flora:

Mexican hat

Rabatida columniferra

Cowpen daisy

Verbesina enceloides

Family: Asteraceae

When seen: 

June 21 2021
Campos Viejos Ranch, 

Rio Grande City (Starr Co.)

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