ID GUIDE TO WILD BEES
OF THE NATIONAL BUTTERFLY CENTER

Mission, Texas

MASKED BEES
Hylaeus

Masked Bees
Genus Hylaeus

Masked bees, sometimes called "yellow-faced bees,"  comprise the genus Hylaeus, and belong to the same bee family -- Colletidae -- as the cellophane bees shown on the previous page of this guide.  

 

Masked bees are easy to overlook -- they're small and slender.  To the casual naturalist, masked bees may look like black ants.

 

Typically, masked bees have yellow designs or "masks" on their faces; parti-colored yellow-and-black legs; and yellow markings on their thoraxes. The bees' abdomens are usually entirely black, without yellow markings, a trait that helps distinguish them from wasps, which often have striped abdomens.

Unusual pollination practices of masked bees

 

Female masked bees do not carry pollen on scopal hairs located on their hind legs or undersides, like most bees.  Instead, female masked bees carry pollen internally, in stomach-like organs. 

 

Female masked bees build nests in the stems of pithy-stemmed plants. The bees secrete a substance said to have a texture similar to polyester, with which they coat the brood cells in which they deposit their eggs. Because of their preference for woody nesting materials, bees of the genus Hylaeus (Latin for  "of the woods")  often abound near woodland habitats.

 

Masked bees have short tongues, but according to the Xerces Society's Guide to Attracting Native Pollinators, the bees' small size allows them to enter into deep-throated flowers to harvest pollen and nectar, unlike large short-tongued bees. 

 

Masked bees  at the National Butterfly Center show a strong preference for small-flowered plants such as goldenrod, Palafoxia and fleabane.  The bees' diminutive size may give them an advantage over larger bees, which may find balancing on small blossoms to too difficult.

Identification Information:   There are more than a dozen species of masked bees in Texas.  All are around ant-sized and easily mistaken for ants. Most are between 4  to 6 mm.  In most species, males are also smaller than their female counterparts. Differentiation among species is difficult to undertake with the naked eye, because the bees are so small and nuances in their appearance minute.  Species identification usually requires the aid of a macro lens or other magnifier.

 

One trait  that helps to distinguish masked bee species from one another is the nature and size of the yellow or white "masks" or markings on the bees' faces.  These vary from one species to another.   Some examples are shown at right.

 

Facial markings also differ in male and female masked bees:  markings of males tend to cover a large area of the face, while on females, the markings are smaller and often restricted to two bands or to two roughly triangular shapes on either side of the bee's face.

Other markings on the bees' bodies are also used to differentiate species.  For example, masks bees often have yellow or pale marks on the tegulae (where the wing joins the body); near the tegulae; and on their legs.  Many masked bees have a collar of yellow lining the front of the thorax (the pronotum).  The size and placement of such markings differs from species to species.

A handful of Hylaeus species, particularly those that inhabit the southernmost arreas of the United States, have exotic coloring on their faces.  For example, the Panamanian masked bee featured below and found at the National Butterfly Center has a partly-orange clypeus (the face part above the jaws).

A female Panamanian masked bee (Hylaeus panamensis)

Comparison of facial markings of six Texas masked bees:  (from left to right) a female affiliated masked bee (top left); a female Panamanian masked bee; a male modest masked bee; a female modest masked bee (bottom left) ; a female Cresson's masked bee; and a male slender-faced bee.   Male bees tend to have masks that cover their entire faces, while females have a pair of roughly-triangular markings that rim their compound eyes.  Masks tend to be pale yellow or white.  On some species such as the Panamanian masked bee, the clypeus (the face part above the bee's jaws) may be orange or yellow.  Differences in facial markings are used to identify Hylaeus species, although in some cases -- such as the female affiliated and female modest masked bee, differences in facial patterns may be negligible.

TAXONOMY OF HYLAEUS BEES

Order:   Hymenoptera 

Family:   Colletidae (plasterer and masked bees)

Genus:   Hylaeus (masked bees)
Subgenus:   Prosopis 

Species found at the NBC: 
      Hylaeus
affinis (Affiliated masked bee) 

      Hylaeus modestus (Modest masked bee)

          

Subgenus:   Hylaeana

Species found at the NBC: 

       Hylaeus panamensis  (Panamanian masked bee)

Masked Bee Species of the National Butterfly Center

Affiliated masked bees (Hylaeus affinis) and the modest masked bee shown below (H. modestus) are very similar and exemplify the difficulty in parsing out different Hylaeus bees into separate species.  Female affiliated and  modest masked bees are similar in size and have nearly identical facial masks; yellow pronotal collars (at the front of the thorax); and pale markings on their legs.  Both species visit a wide range of plants and are found throughout the United States

 

One minute trait that sometimes helps distinguish female Hylaeus affinis from Hylaeus modestus females is that on  H. affinis,  there are pale markings on the female bee's tegulae (the nodes where the wings join the body), and on the smaller, tegula-like structures partly hidden under the tegulae.   These are shown in the photo strip above left.  Hylaeus modestus lacks yellow markings on these body parts.

Panamanian Masked Bee

Hylaeus (Hylaeana) panamensis

Family:  Colletidae

Size:      4.5 mm (female)

Associated plants at NBC:  

Texas palafox

(Palafoxia texana)   
Plant Family: Asteraceae

 

When Seen:

November 2019

Hylaeus panamensis masked bee - Copyright 2019 Paula Sharp

A female Panamanian masked bee

Show more.
Hylaeus panamensis masked bee - Copyright 2019 Paula Sharp

Face of a female Panamanian masked bee

Masked bees of the subgenus Hylaeana are small (3.5 – 4.5 mm) and have pitted thoraxes; and abdomens with unpitted, smooth surfaces on the first two segments. 

 

The orange clypeus of the female bee shown here is an unusual trait in masked bees.  Only a handful of North American masked bees have partly or mostly orange-yellow clypeuses.  (Among these are Hylaeus flammipes, H. formosus, H. rudbecki and H. volusiensis) Hylaeus formosus belongs to the same subgenus (Hylaeana) as the Panamanian masked bee, but within the United States is found only in Florida. and its first abdominal segment is reddish orange.  The Panamanian masked bee, by contrast, has an entirely black abdomen.

 

The Panamanian masked bee is considered a neotropical species, and is found from Panama through the southwestern United States.  Jack Neff, President of the Central Texas Melittological Institute, has noted that within Texas, this species occurs near the border, principally in Hidalgo and Cameron Counties; he has seen one specimen from Edwards County.

Hylaeus affinis masked bee - Copyright 2019 Paula Sharp

A female Hylaeus affinis masked bee

Hylaeus affinis masked bee - (c) Copyrigth 2019 Paula Sharp

Face of a  female Hylaeus affinis masked bee

Affiliated masked bees (Hylaeus affinis) and the modest masked bee shown below (H. modestus) are very similar and exemplify the difficulty in parsing out different Hylaeus bees into separate species.  Female affiliated and  modest masked bees are similar in size and have nearly identical facial masks; yellow pronotal collars (at the front of the thorax); and pale markings on their legs.  Both species visit a wide range of plants and are found throughout the United States

 

One minute trait that sometimes helps distinguish female Hylaeus affinis from Hylaeus modestus females is that on  H. affinis,  there are pale markings on the female bee's tegulae (the nodes where the wings join the body), and on the smaller, tegula-like structures partly hidden under the tegulae.   These are shown in the photo strip above left.  Hylaeus modestus lacks yellow markings on these body parts.

Modest Masked Bee
Hylaeus  (Propsopis) modestus

Family:  Colletidae
Size:  5-7 mm (male)

          4.5-7 mm (male)

Food plants at NBC:  
 

(Croton humilis)
Plant Family:  Euphorbiaceae

When seen:

November 2018  

Masked bee - Hylaeus modestus - (c) Copyright 2019 Paula Sharp

A male modest masked bee

Hylaeus modestus - modest masked bee - (c) Copyright 2019 Paula Sharp

A male modest masked bee

Hylaeus modestus modest mske bee - (C) Copyrght 2019 Paula Shap

A female modest masked bee

As noted in the entry above, Affiliated masked bees (Hylaeus affinis) and the modest masked bee (Hylaeus modestus) shown are very similar.

Male modest masked bees can be told from male Hylaeus affinis by examining the antenna scapes (the bottom antennal segments).   The scapes of Hylaeus modestus males are black, while those of  H. affinis males have yellow markings on them.

Generally, the face of the male H. modestus has a yellow facial mask whose outer edges generally follow the inner edge of the bee’s compound eyes, from the lowermost to the tip of each mark.  Although the male bee’s antennal scapes are black, the rest of each antennae is dark above and golden brown below.  Most, but not all male H. modestus have a yellow pronotal collar (at the front of the thorax.) On some male modest masked bees (but not the females), there is a yellow mark on each tegula (the node where the bee’s wing meets its body) and on the smaller tegula-like plate partly hidden underneath it. 

Affiliated Masked Bee

Hylaeus (Prosopis) affinis

Family:  Colletidae

Size:      6.5 mm (female)

Associated plants at NBC:  

Texan palafox

(Palafoxia texana)   
Plant Family: Asteraceae

 

When Seen:

November 2019

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