ID GUIDE TO WILD BEES
OF THE NATIONAL BUTTERFLY CENTER

Mission, Texas

TETRALONIELLA LONG-HORNED  BEES
Tetraloniella / Eucera

TETRALONIELLA  LONG-HORNED BEES

Genus Tetraloniella (before 2018)
Genus Eucera (after 2018) 

Until quite recently, the bee shown at right was known as Tetraloniella willmattae. 

Before 2018, Tetraloniella was a recognized genus of pollinators belonging to the long-horned bee tribe Eucerini.  Bees labeled Tetraloniella still appear in popular bee guides and in several prominent Internet databases, including Bug Guide, Discover Life and the Encylopedia of Life.  Nonetheless, in 2018, changes shook the entomological world, and the lovely name Tetraloniella has been cast aside and assigned to the obscurity of discontinued bee genera.

The genus Tetraloniella was first named and described by entomologist William Harris Ashmead.  Born in 1855, Ashmead served as a field entomologist for the Florida Department of Agriculture, wrote more than 250 scientific articles and worked in the last years of his life at the National Museum of Natural History in Washington, D.C.  In 1899, while employed at the museum, Ashmead coined the genus Tetraloniella, based on a description of a single female long-horned bee, which appeared in the journal Transactions of the American Entomological Society.

Prior to 2018 upheavals in the long-horned bee world, the most comprehensive attempt to tackle the genus Tetraloniella was “Revision of the bees of the genus Tetraloniella in the New World (Hymenoptera: Apidae),” published by the famed entomologist Wallace E. LaBerge in 2001. For this work, LaBerge examined 6,504 specimens of Tetraloniella, boiling them down to 35 distinct species, which he described in painstaking detail.  Among these was Tetraloniella wilmattae, featured on this guide page.

LaBerge generally described Tetraloniella as follows:  They are small to moderate-sized bees that superficially resemble long-horned bees of the genus Melissodes (shown here below right). The abdomens of Tetraloniella are often striped with bands of 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 jaws, clypeuses and labrums (the mouthparts situated above and between the jaws). Some males have toothlike projections on either side of the sixth segment of their abdomens.

LaBerge nonetheless expressed some reservations about the genus Tetraloniella.  He concluded that “current knowledge of this interesting genus is incomplete” and noted that some outliers labelled Tetraloniella were difficult to reconcile with any uniform standard for the genus, and appeared to fit just as easily into other genera.

LaBerge was joined by the prominent entomologist Charles Michener, who groused about the genus Tetraloniella in his voluminous The Bees of the World.  Michener pronounced the genus difficult to define, noting that it was geographically far-flung, comprised of subgenera living in the United States, Canada, Mexico, Central Asia, India, Europe, sub-Saharan Africa and Madagascar.

 

Michener compared Tetraloniella to the much larger long-horned bee genus, Eucera, writing that Tetraloniella long-horned bees were generally smaller than Eucera, with less protuberant clypeuses.  Michener then enumerated several exceptions to these generalizations, ultimately concluding about Tetraloniella: "This classification is anything but satisfying but represents the current stage of knowledge of this group." 

Such dissatisfactions in the entomological world led to efforts in 2018 to sink the genus Tetraloniella.

The abandonment of the genus Tetraloniella

By 2013, The Field Guide to the Common Bees of California reported that there were 117 species of Tetraloniella recognized worldwide.  In 2016, Wilson & Carril’s The Bees in Your Backyard reported 22 species of Tetraloniella within the United States alone.  Such field guides struggled valiantly to describe the genus, usually seeking refuge in vague generalizations, noting, for example, that Tetraloniella  were smaller than the typical Eucera; that Tetraloniella tended to fly in the spring, rather than the summer-fall period typical of Melissodes; that like almost all long-horned bees, Tetraloniella lived in the ground and were solitary, but at times, perhaps, communal; that they were pollen specialists but generalists as well, etc. 

Ultimately, in 2018, a group of entomologists named Dorchin, Lopez-Uribe, Praz, Griswold and Danforth published a study titled “Phylogeny, new generic-level classification, and historical biogeography of the Eucera complex (Hymenoptera: Apidae)”.  Dorchin et al. described the classification system for Eucerini as sprawling and messy, and they demanded a rehaul, based in part on a new analysis of DNA sequencing in various Eucerine groups.

The consequences of this declaration are seismic in the universe of long-horned bee names:  if you enjoy the labyrinthine annals of entomological taxonomy, you may click here for a detailed explanation of the reclassification of long-horned bees  generally and Tetraloniella specifically. 

Alternately and briefly:  Dorchin et al. proposed, among other changes, that bees occupying the genus Tetraloniella be resituated in the genus Eucera, and that the illustrious name Tetraloniella be abandoned entirely.  New World Tetraloniella like the T. wilmattae shown on this guide page were placed within a new subgenus, Xenoglossodes

 

Thus, if you subscribe to the new classification system, the new scientific name of the little bee  shown on this page is now:  Eucera (Xenoglossodes) wilmattae.

Eucera (Xenoglossodes) wilmattae

Unaware of their wholesale reclassification, Eucera wilmattae long-horned bees visit aster-family flowers during late fall at the National Butterfly Center. 

 

This species is also known by the common name Wilmatte's long-horned bee.  In November 2018, and again in April 2019, male Wilmatte's long-horned bees were frequent visitors to NBC skeleton-leaf goldeneye, a yellow-flowered aster-family plant that blooms in the Lower Rio Grande Valley through late November. 

Wilmatte's long-horned bees are enchanting insects. Males have bright yellow faces and exceptionally long antennae, which they curl inward at the tips, perhaps in an effort to keep them from snagging on flowers and leaves.  Both males and females have striking 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 male Melissodes long-horned bees at the NBC, which have brightly-colored (usually green or blue-gray) eyes. Detailed photographs of Wilmatte's long-horned bees are shown below.

This species was named after the entomologist-botanist Wilmatte Porter Cockerell, who first described 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. The bee was feeding on a yellow aster-family flower.

Cockerell did not place her long-horned bee in the genus Tetraloniella:  she located it instead in Xenoglossodes, a genus defined by Ashmead when he invented Tetraloniella.  Cockerell called her newly found species Xenoglossodes wilmattae.

 

Xenoglossodes wilmatte retained its name until 2001, when LaBerge declared that the genera Tetraloniella and Xenoglossodes were duplicative.  He dispensed with the genus Xenoglossides, and renamed Wilmatte's longhorned bee Tetraloniellla wilmattae. It retained that name until 2018, when it was rechristened, yet again, as Eucera (Xenoglossodes) wilmattae.

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

A male Wilmatte's long-horned bee (Tetraloniella wilmattate / Eucera wilmattae)

Tetraloniella wilmattae - (c) Copyright 2018 Paula Sharp

A male Wilmatte's long-horned bee:   Note the yellow clypeus and exceptionally long antennae.
 

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

A female Wilmatte's long-horned bee

Tetraloniella wilmattae female and male long-horned bees

Female and male Wilmatte's long-horned bees

Tetraloniella wilmattae - (c) Copyriht 2019 Paula Shrp

Female and male Wilmatte's long-horned bees

TAXONOMY  OF  TETRALONIELLA 
(old nomenclature)

Order:   Hymenoptera

Family:   Apidae

Subfamily:  Apinae

Tribe:  Eucerini

Genus:   Tetraloniella
Species found at NBC:
    Tetraloniella wilmattae

 

TAXONOMY  OF  EUCERA
(post 2018 nomenclature)

Order:   Hymenoptera

Family:   Apidae

Subfamily:  Apinae

Tribe:  Eucerini

Genus:  Eucera

Subgenus:   Xenoglossodes
Species shown below:
   Eucera wilmattae

CITE THIS PAGE:  Sharp, Paula and Ross Eatman. "Tetraloniella long-horned Bees."  Wild Bees of the National Butterfly Center of Mission, Texas.  15 Jan. 2019,  http://www.sharpeatmanguides.com.  Accessed [day/month/year guide accessed].   

Tetraloniella (Eucera) Species of the National Butterfly Center

Wilmatte's Long-horned Bee

Tetraloniella (Tetraloniella) wilmattae

aka Eucera (Xenoglossodes) wilmattae

Family:  Apidae

Size:  10 mm - 2/5" 

Associated  plants at NBC:  

Skeleton-leaf goldeneye
(Viguiera stenoloba)
Plant Family: Asteraceae)

November 2018; April 2019  

Species characteristics:  Look for a bee with pale hairs on its head, thorax and legs; pale bands of hair on its abdomen and opaque black eyes.  Male bees have particularly long antennae, often curled at the ends. A hallmark of males of this species is that the top 3 1/2 segments of each antenna are dark.  Male bees have bright yellow faces and jaws.  Females have shorter antennae and black faces covered with pale hairs; and a narrow pale-yellow strip on the bottom of the clypeus (just above the jaws).  The hairs on males' heads and bodies are pale; on females, the hairs are pale golden brown.

Male bee

Show more.

Female bee

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

A male Wilmatte's long-horned bee

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

A male Wilmatte's long-horned bee

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

A female Wilmatte's long-horned bee

Permissions and Copyright Information:   All images on this site are (c) Copyright 2018-2019 Paula Sharp and Ross Eatman.  All rights reserved. All photographs are protected by registered copyright.  Please contact Sharp-Eatman Nature Photography for written permission before using any of these images for any purpose. 

Last updated November 2019

 1-15-19