top of page

This page features four bee genera belonging  to the tribe Osmiini:  Osmia, Hoplitis, Chelostoma and Heriades.  Members of these genera are commonly known as mason and resin bees.

Mason bees derive their name from their practice of mixing soil and other materials in order to build nest structures in which to lay eggs.  Resin bees gather plant saps, or resins, which they use to seal nest entrances.

Mason and resin bees are typically solitary:  they construct individual nests in hollow reeds, or in pre-existing cavities found in dead wood, plant matter, cast-off snail shells or other litter, or, less commonly, in the ground.


Female mason and resin bees carry pollen on scopal hairs located on the sternum (underside of the abdomen), a trait that helps identify them -- and which they share with other members of the Megachilidae family, such as leafcutter and carder bees.  Mason and resin bees possess other distinctive traits.  Their forewings have two submarginal cells (rather than the more common three).  The tarsal claws of mason bees' front feet also sport have pads called arolia.  These features are shown in the photo strip here.

​OSMIA MASON BEES:   The common name "mason bee" is most often used in reference to bees of the genus Osmia.  These bees are fast fliers and energetic and important crop pollinators.  Throughout North America, orchard owners use Osmia mason bees to pollinate spring-flowering fruit and nut trees. Commerical bee houses are often used to attract and house Osmia.


Osmia mason bees are small-to-medium-sized, with robust builds and relatively large heads.  In our area, Osmia  tend to fall into three subgenera:  Helicosmia (usually metallic green or blue with pale hairs, and sometimes with pale abdominal bands as well); Melanosmia (usually robustly-built and metallic green or black); and Osmia (which includes two imported species, the hornfaced bee and the bull mason bee). 


At least 25 Osmia species are native to New York.  A sampling of Osmia found in Rockfeller Park Preserve and Stone Barns Center for Food & Agriculture is shown below.  In addition to being useful fruit and nut pollinators, wild Osmia are efficient pollinators of wildflowers and garden flowers. 

HOPLITIS MASON BEES :  Hoplitis are pollinators of woodland trees and shrubs, garden flowers and berries; they also visit some varieties of commercial fruit. These members of the tribe Osmiini have slender bodies markedly different from that of the typical Osmia.   Hoplitis mason bees of our region tend to be small and black or darkly-colored, with pale abdominal hair bands.

Hoplitis use chewed leaves, dirt, pebbles or wood particles to construct walls between the brood cells of their nests.  Seven Hoplitis species are found in New York.

CHELOSTOMA MASON BEES:  The genus Chelostoma is represented in New York by s single native species, the mock orange chelostoma. This species has a singular appearance: it is an antlike bee with disproportionately long jaws. Chelotoma mix plant saps with fine pebbles to cement their nests together.

Bees of the genus Chelostoma tend to be specialist pollinators.  Thus, the mock orange Chelostoma is principally a pollinator of mock orange. Two other non-native Chelostoma species found in New York are pollinators of bellflowers. 

HERIADES RESIN  BEES:   Heriades of North America are small, dark bees with pitted heads and bodies, and abdomens banded by pale hairs.   They are generalist pollinators that use plant resins and saps to plug the entrances to the their nests.  There are four Heriades species in our area.


Osmia Mason Bees

FAMILY: Megachilidae
SUBFAMILY:  Megachilinae
TRIBE:  Osmini
GENUS:  Osmia
SPECIES SHOWN BELOW:  Osmia georgica,
O. pumila, O. bucephala, O. cornifrons, O. taurus

Hoplitis Mason Bees

FAMILY: Megachilidae
SUBFAMILY:  Megachilinae
TRIBE:  Osmini
GENUS:  Hoplitis
SUBGENUS SHOWN BELOW :  Alcidamea sensu stricto

Chelostoma Mason Bees

FAMILY: Megachilidae
SUBFAMILY:  Megachilinae
TRIBE:  Osmini
GENUS:  Chelostoma
SPECIES SHOWN BELOW :  Chelostoma philadelphi

Heriades Resin Bees

FAMILY: Megachilidae
SUBFAMILY:  Megachilinae
TRIBE:  Osmini
GENUS:  Heriades 
SPECIES SHOWN BELOW : Heriades carinata, H. variolosa/leavitti

An Osmia mason bee

Hoplitisson Bee - (c) 2016 Copyright 2015 Sharp-Eatman Photo

Hoplitis mason bee

Chelostoma philadelphi - (c) 2017 Copyright 2015 Sharp-Eatman Photo

A Chelostoma mason bee


A Heriades resin bee

Common traits of mason bees


Chelostoma philadelphi


Tribe Osmiini:  Osmia, Hoplitis, Chelostoma & Heriades

Subgenus Helicosmia

Osmia Georgica Mason Bee

Osmia georgica 

1/4" - 3/10" (small)

The beautiful Osmia georgica mason bee emerges in early to mid-May in our region and visits various woodland wildflowers, including wild geraniums, members of the aster family and the blossoms of wild berries.  Osmia georgica  are also documented pollinators of a variety of crops, among them apples, melons, squash and cucumbers.

Osmia georgica mason bees are a relatively rare sight in Westchester County. These bees appeared, however, for three consecutive springs (2015-2017) in Rockefeller State Park Preserve.  During this period, enhanced trail management at the park  resulted in increased numbers of spring wildflowers.  In late May, 2016 and 2017, the humble wildflower known as common fleabane (Erigeron philadelphicus) appeared in the park in unusual abundance along trail edges. Wherever this flower flourished, Osmia georgica seemed to follow; multiple bees often appeared on single plants in the Swan Lake area. 

Like mason bees generally, Osmia georgica are solitary.  They nest in hollow stems, in holes found in trees, in abandoned nests of other bees and in cavities found in clay banks. Female Osmia georgica are energetic pollen-gatherers that sometimes exhibit striking behavior when foraging:  when pollinating fleabane, for example, they position their heads in the center of the fleabane flower and whirl around in circles.

Osmia georgica belong to the subgenus Helicosmia.  As noted in this guide page’s introduction, mason bees of this subgenus tend to be metallic green or blue with pale hairs.  According to Charles D. Michener's The Bees of the World, female bees of this subgenus characteristically have four tufts of orange hair beneath the clypeus (the face-part above the mandibles).  All of these traits are possessed by Osmia georgica, as shown in the photos here.

Identification Information:   Osmia georgica are fairly small for mason bees.  The two female Osmia georgica shown here were between 1/4" and 3/10" long.  Viewed with the naked eye, Osmia georgica appears a dark metallic blue-green with dark wings, legs and antennae.  Viewed minutely, the bee has pale hair on its head and thorax and pale hair bands on its abdomen.  These bands may be difficult for the casual observer to see; they are most apparent when the bee is viewed from the side. The bee’s hair bands help distinguish Osmia georgica from similar metallic mason bees that lack such banding.

Female Osmia georgica are fairly easy to identify, because the scopal hairs located under their abdomens are a bright orange, a trait shared by only a handful of mason bees in our area. Most mason bees of the American northeast have either black or pale scopal hairs; notable exceptions are the imported species, hornfaced bees and bull mason bees, shown at the bottom of this guide page – but these bees are considerably larger and brown to black, rather than metallic green, and thus easy to tell apart from Osmia georgica.

Osmia georgica also have distinctive growths on their mandibles. When viewed in profile (as shown in the photostrip here), two toothlike projections can be seen protruding from the bee's face above its jaws.  According to bee expert and biologist Sam Droege, the Osmia probably use these to help carry mud to the nests, for use in nest construction.

Seen by the naked eye, Osmia georgica mason bees can be confused with small carpenter bees and dark sweat bees.  The best way to distinguish females is by their habit of transporting pollen on scopae (brushes) located under their abdomen. Mason bees of both sexes are generally hairier than sweat bees.   Small carpenter bees and club-shaped abdomens. In addition, viewed minutely, male and female Osmia have only two submarginal cells in their forewings.

Osmia georgica Mason Bee - (c) 2016 Copyright 2015 Sharp-Eatman Photo

A female Osmia georgica mason bee with orange scopal hairs

Osmia georgica Mason Bee - (c) 20016 - Copyright 2015 Sharp-Eatman Photo

Face of a female Osmia georgica

All photos (c) 2014 - 2016 Sharp-Eatman Nature Photography

Subgenus Melanosmia

Osmia (Melanosmia) Mason Bees

(Subgenus Melanosmia spp.)
approx. 1/3" - 3/5" (medium-sized)

During spring and early summer, Rockefeller State Park Preserve and Stone Barns Center for Food & Agriculture abound with metallic blue-green mason bees that belong to the subgenus Melanosmia. 


Melanosmia mason bees first become visible in the park as early as April, pollinating spring-blooming willows and woodland ephemerals such as trout lilies and claytonia.  In late spring and early summer, Melanosmia appear in the park feeding on penstamon, wild geraniums, bowman's root and wild blackberries and strawberries.  At Stone Barns, Melanosmia can be observed throughout spring, pollinating apples and blueberries. 

Feeding habits among  various New York Melanosmia differ. Some New York Melanosmia species specialize in a fairly narrow range of plants, such as the relatively uncommon Osmia inermis, which shows a preference for heather; and Osmia inspergens, which favors blueberries and members of the pea family.  Other Melanosmia, such as the Bufflehead mason bee (Osmia bucephala) and the dwarf mason bee (Osmia pumila), shown below, range on a wider array of plants.

The nesting habits of many Melanosmia species have not been fully explored through entomological research.  Known nesting habits vary considerably among species. Many Melanosmia construct their nests of chewed leaves or rootlets found in the ground abutting nesting sites.  Melanosmia   may excavate nests in the dead or fallen branches of trees and shrubs; underneath tree bark; in the ground; in stumps or dense grass tussocks; in holes burrowed by other insects into wood; or in holes drilled into human-made wood blocks. Still others, such as Osmia inermis, attach their brood cells to the undersides of rocks or discarded pottery, or ensconce them in pre-existing holes found in walls.  Although Melanosmia are characteristically solitary bees, some work cooperatively:  for instance, several female Osmia inermis may live communally, building their nests together under a single stone.

There are at least 17 species of Melanosmia in New York. (Species documented in southern New York where the preserve is located include, among others, Osmia albiventris, Osmia bucephala, Osmia collinsiae, Osmia distincta, Osmia felti, Osmia inermis, Osmia inspergens, Osmia pumila and Osmia sandhousae.)  The majority of these are somewhat smaller than honey bees, with shimmering blue-green bodies sparsely covered with pale hairs.  Females usually sport white scopal hairs under their abdomens.  Such bees may be very difficult to distinguish from one another, and species identification may require minute inspection by an expert.

A few local Melanosmia species are easier for the casual observer to identify because they have unusual or distinctive characteristics -- these include the bufflehead and dwarf mason bees shown below.  

Osmia (Malnosmia) mason bee - (c) 2017 Paula Sharp

A female Osmia (Melanosmia)

Osmia (Malnosmia) mason bee - (c) 2017 Paula Sharp

An Osmia (Melanosmia) on Bowman's Root.

Osmia (Malnosmia) mason bee - (c) 2017 Paula Sharp

An Osmia (Melanosmia) pollinating penstamon

Subgenus Melanosmia

Dwarf  Mason Bee

Osmia pumila

1/4" (males)  - 3/10" (females) (small)

​​Osmia pumila is one of several metallic blue-green mason bee species belonging to the subgenus Melanosmia.  In this group, this bee is distinctive in part because of its size. Pumila means "dwarf" in Latin:  the male of this species is among the smallest Osmia found in the Northeast; the female is only slightly bigger.

These mason bees emerge in April in the park, when they can be spied pollinating spring bulbs such as trout lilies and claytonia.  Osmia pumila linger in the park through the end of June. They are frequent visitors of wild geraniums and the orange milkweed variety known as butterfly weed.  The bee shown here was found feeding during June on wild geraniums.

Osmia pumila  favor forest and wetland habitats.  These bees build solitary nests in the dead pithy stems of plants such as elderberry and roses and in holes found in rotted wood.  Osmia pumila nests are tubular in form, with entrances and outer chambers on either end and brood cells in between.  The bees use chewed plant material such as leaf pulp to form partitions between cells and to plug the ends of their nests.

In addition to visiting many woodland wildflowers, Osmia pumila are useful pollinators of apples, blueberries, strawberries, and caneberries. These small mason bees also pollinate woodland trees and shrubs, among them willow, redbud, dogwood, sassafras, viburnum and hawthorn. 

Osmia pumila are sometimes preyed on by the cleptoparasitic bee Stelis lateralis and by the cleptoparasitic wasp Sapyga centrata.  Parasitism by such species may increase where food sources for the mason bees are in short supply.

​​​Identification Information:   Osmia pumila are usually between  3/10" and 2/5” in size; males tend to be are smaller than females.  Both are a dull metallic blue-green on close inspection, although from a distance the bees appear dark and even black when not illuminated by sunlight.  Males appear a shiny yellowish olive-green in bright light; females are a bluer green.  Osmia pumila have pale hairs on their heads, thoraxes and abdomens.  Females have white scopae on the sternum, used to transport pollen.


In the Northeastern United States, there are several  Melanosmia species that possess all of the above traits.  Differentiating among these species requires expert assistance and may hinge on such subtle differences as the width and appearance of hair bands rimming the bee’s abdominal segments.

Seen by the naked eye, Osmia pumila can be confused with small carpenter bees and dark sweat bees.  The best way to distinguish femaleis by their habit of transporting pollen on scopal hairs located under their abdomen, in the way characteristic of Osmia. Mason bees of both sexes have stout, cylindrical bodies and are generally hairier than sweat bees and small carpenter bees. In addition, viewed minutely, Osmia pumila have only two marginal cells in their wings, as shown in the photos here.

Osmia pumila mason bee - Copyright 2016 Sharp-Eatman Photo

A female Osmia pumila mason bee

All photos (c) 2014 - 2016 Sharp-Eatman Nature Photography

Subgenus Melanosmia

Bufflehead Mason Bee

Osmia bucephala 

(Subgenus Melanosmia)

1/2" - 3/5"   (medium-sized)

​Bufflehead mason bees appear in the park and at Stone Barns Center for Food & Agriculture in early April, when temperatures are still chilly and occasionally dip into the thirties; they remain in our area until mid-June.  These bees are singularly hardy in cold temperatures; Osmia bucephala are found as far north as the Yukon.

Bufflehead mason bees nest in cavities in dead wood or in the hollow dead stems of pithy plants such as elderberries. The bees construct walls between their egg cells with leaf or wood pulp scraped from the cavities’ interiors. In our experience, bufflehead mason bees tend to lurk around flowering plants at ground level, stopping to rest on bare earth.  When visiting flowers, bufflehead mason bees often pause to rest on leaves beside the blossoms, sunning themselves.

These bees are solitary, like the other mason bees on this page.  Nevertheless, Osmia bucephala may build nests close to one another.  Females have been known to establish nests beside those of other species of mason bees as well, in bee houses set out by orchard growers to accommodate commercially purchased Osmia such as blue orchard bees.  (An example of such a house is shown near the top of this guide page.) 

Osmia bucephala are pollinators of early spring wildflowers such as bluebells and trout lilies, and of native spring-blossoming trees and shrubs, among them ninebark, black chokecherry, redbud and dogwood.  Bufflehead mason bees also can be found pollinating garden azaleas, false blue indigo and lilacs. The male bee shown here was feeding on blueberry blossoms in the park during late April.  The female bee was found foraging on false indigo flowers in Stone Barns gardens during early June.

Identification information:  “Buffle,” according to the Merriam-Webster Dictionary, is short for “buffalo.”   Apparently the entomologist who named this mason bee thought that the female bee's large shaggy head made it look like a buffalo.  The most salient characteristic of this species is its robust size, unusual in mason bees of the American northeast.


Male and female bufflehead mason bees differ considerably in appearance.  ​​Females are more robust than males, and males lack the buffalo-like heads.  Males have a strong metallic blue sheen, while females appear black from a distance -- although under intense light, females' heads show metallic blue highlights.


The thoraxes of male bufflehead mason bees sport ruffs of pale hair, and their faces are covered with tufts of light hairs, as shown in the photo at top right. The first two segments of the male bee’s abdomen (T1-T2)  are metallic blue with sparse light-colored hairs, and the rest of the segments are covered with black hairs or dark hairs intermixed with pale ones. The male bee's black legs are also distinctive:   segments of the bee's tarsi (the lower leg parts) flare outward.

On first glance, the heftier female bufflehead mason bee can be mistaken for a bumble bee, because of its robust build and hairy, yellow-and-black appearance:  yellow hairs cover the top of the bee’s head and thorax and the first two segments of the bee’s abdomen; black hairs cover the remaining segments.  The scopal hairs on the underside of the bee's abdomen, which it uses to collect pollen, are black.  The large head of the female bufflehead bee has a distinctive groove across the base of the mandibles.  The bottom of the female bee’s clypeus (the face-part above the mandibles) is thickened and protuberant, as shown in the photostrip here.

A male Osmia bucephala

A male bufflehead mason bee

A male Osmia bucephala

A female bufflehead mason bee

All photos (c) 2014 - 2024 Sharp-Eatman Nature Photography

Osmia Mason Bees

Genus Osmia, Subgenus Osmia

Hornfaced Bee

Osmia cornifrons

(Subgenus Osmia)

3/10"  - 1/3"  (medium-small)

Hornfaced bees belong to the redundantly named subgenus Osmia.  In New York, only two mason bees -- the hornfaced bee and the bull mason bee shown below -- represent this subgenus, and both are invasives originating in Asia. 


In the 1960s, the United States Department of Agriculture hit on the idea of importing hornfaced bees from Japan, believing these insects might be better pollinators than honey bees. Why the USDA pursued exotic mason bees when we have a nice supply of our own remains a good question.  Over the next fifty years, hornfaced bees, as they are now commonly called, established themselves along the eastern coast of America, pollinating fruit trees with extraordinary efficiency and escaped from orchards into woodlands.  This species is now endemic to many northeastern states, among them Pennsylvania and New York.

Entomologists have expressed concern that these bees may have a negative impact on native mason bee species such as the blue orchard bee (Osmia lignaria).  In addition, 

shipments of  hornfaced bees have contained unianticipated stowaways -- the bull mason bee (shown below) and a parasitic Monodontomerus wasp. 


Nevertheless, it is notable that hornfaced bees are docile and rarely sting. And, their formal status as an exotic species notwithstanding, hornfaced bees have fulfilled their promise as pollinators. In Japan, hornfaced bees were used principally as apple pollinators at the time of their importation here. The bees have been described since by scientific teams in the United States as being 80 times more effective than honey bees in pollinating American apples. A hornfaced mason bee can visit fifteen flowers per minute and set 2,450 apples per day.  


The hornfaced bees shown here were found in woods bordering Stone Barns Center for Food and Agriculture.  Although Stone Barns cultivates many fruit tree varieties, the Center did not introduce these bees -- they arrived on their own, setting themselves up in a rotted tree trunk a few yards from a self-seeded cherry tree in a wooded area, and about one hundred yards from Stone Barns' fruit tree groves. 


These bees can be spied exiting and entering small holes in rotted tree trunks, where they nest.  Although the bees are solitary, they like to inhabit nests near one another. Males can  be observed  basking on rocks and leaf litter in early spring. They do this to warm their body temperatures and to lie in wait for mates.  Females tend to emerge 2 to 3  days after males, or slightly later, depending on weather.  Mating begins immediately after females emerge. The females then commence gathering pollen and establishing nests in holes in trees or hollows in dead plant stems. 


Identification Information:   The male Osmia cornifrons shown here has a black body covered with tan hairs.  From a distance, the bee has a furry appearance; its abdomen is encircled with sashes of light brown hair.  The bee has a wide, bulky head and a tear-shaped thorax that joins its abdomen in a narrow waist.  Osmia cornifrons hold their wings in a distinctive way, in a rough V-shape, with the wing tips angled outward at the back. Males have white hair on their faces, as shown in the photostrip at right.  The faces of female Osmia cornifrons have hornlike protrusions in front.


These bees are easy to confuse with the stowaway species, Osmia taurus, which arrived with them in the U.S. in the 1960’s.  Osmia taurus can be distinguished, because their hairs are  partly rust-colored, while those of hornfaced bees are generally tan or light brown.  Observed minutely, hornfaced bees also show some black hairs intermingled with the lighter ones, while Osmia taurus lacks black hairs. 


Osmia cornifrons appears in the woodlands bordering Stone Barns very early in spring -- in late March -- and disappears by the end of April.  This species produces only one generation each year.  Hornfaced bees are also known by the name Japanese Orchard Bee.

Hornfaced Bee - Osmia cornifrons Mason Bee - c) Copyright 2016 Sharp-Eatman Photo

A male hornfaced bee

Hornfaced Bee - Osmia cornifrons Mason Bee - c) Copyright 2016 Sharp-Eatman Photo

A male hornfaced bee

All photos (c) 2014 - 2016 Sharp-Eatman Nature Photography

Genus Osmia, Subgenus Osmia

Bull Mason Bee

Osmia taurus

(Subgenus Osmia)

3/10"  - 1/2"  (medium-sized)

As noted in the above guide entry, bull mason bees came to the United States in the 1960's as stowaways on shipments of hornfaced bees imported from Japan by the United States Department of Agriculture. Like hornfaced bees, bull mason bees are native to Asia, but have established themselves in woodlands and orchards in the American Northeast.


These bees appear in woodland areas bordering Stone Barns just as apple trees begin to flower, around the third week of April.  Osmia taurus are documented pollinators of apples and berries.  They are also known to pollinate the spring woodland bulb known as the trout lily, which blooms in the same period as apples in our area. 


Like hornfaced bees, bull mason bees produce only one generation each year in our area.  They tend to nest in cavities in trees and logs.  Since the 1970's, Osmia taurus has made its way progressively south through the Mid-Atlantic states.  Its expansion is of some ecological concern because Osmia taurus may be disruptive to other cavity-nesters and out-nest native Osmia species.


Identification Information:   The bee shown here is an Osmia taurus female.  It is the size of a typical honey bee and has a robust build.  From afar, the bee has a furry appearance; its head, thorax and abdomen are covered with hairs, and it has long scopal hairs on the sternum (underside of its abdomen).  This bee is similar in appearance to the hornfaced bee in the above entry, but the bull mason bee has distinctive rust-red hair on its legs, thorax and sternum. 


As shown in the photostrip here, the female Osmia taurus has two bullhorn-like protruberances on its face, positioned over a pair of formidible mandibles.  Males lack horns but have unusually long antennae.  Males also have white hairs on their faces.

Osmia taurus female (bufflehead mason bee)

A female bull mason bee

All photos (c) 2014 - 2016 Sharp-Eatman Nature Photography

Hoplitis Mason Bee

(Subgenus Alcidamea sensu stricto)

1/4" (small)

Like Osmia mason bees, Hoplitis belong to the tribe Osmiini of the family Megachilidae As noted in the introduction to this guide page, Hoplitis are insect-masons that construct walls between the brood cells of their nests.  Hoplitis females carry pollen on scopal hairs located under their abdomens.

​​Like all the Osmia species shown above on this page, Hoplitis are solitary. According to entomologist Charles D. Michener, the nests of Hoplitis take many forms. Some Hoplitis nest in the stems of pithy plants and make partitions between cells with plant pulp, sometimes mixed with pebbles or wood particles. Other Hoplitis construct cell walls of resin mixed with plant bits inside the pre-existing cells of abandoned wasp nets.  Still others nest in the ground and build nest partitions using  soil or clay, sometimes lining cell walls with flower petals.

There are seven species of Hoplitis in New York. Hoplitis in our area tend to be small, with narrow bodies markedly different from those of the typical Osmia. Most Hoplitis are black or dark ly-colored, with pale hair bands on their abdomens.

The Hoplitis mason bee shown at right belongs to the subgenus Alcidamea sensu strictothree New York species, nearly identical to the naked eye, belong to this subgenus (H. producta, H. pilosifrons, and H. truncata).  These bees form nests in plants with pithy stems, such as elderberry, and partition their brood cells with materials made from chewed leaves mixed with wood and soil debris. The bee shown here was found emerging from the dead branch of an elderberry shrub in early June, before the bloom season for the park's wild elderberries. 

Hoplitis (Alcidamea) forage on a vast array of native wildflowers, garden flowers and shrubs.  They are generalist pollinators that feed on such plants as sumac, dogbane, roses, cherry trees, caneberries,  blueberries, melons and squash.


Identification Information:   In New York,  Hoplitis (Alcidamea) are slender and dark with pale hairs that may form pale bands.  Females tend to have robust, three-toothed mandibles.  Male Hoplitis producta and H. pilosifrons have distinct antennae; the segment at the tip of each antennae is hooked. 

The female Hoplitis shown here is black with a long, parallel-sided body.  The bee's antennae and legs are black, and its eyes are dark olive-green. There are four bands of white hairs on its abdomen -- the fifth abdominal segment (T5)  lacks a band, and on the first two segments, the bands are interrupted in the middle.  The bee was transporting dry yellow pollen on white scopal hairs located on its sternum.

Hoplitis can sometimes be confused with small leafcutter bees.  A simple way to distinguish them is that North American leafcutter bees lack arolia (small pads) on their feet, while the tarsal claws of Hoplitis have arolia. 

Hoplitis Mason Bee - Subgenus Alcidamea sensu strictu - (c) 2016 Sharp-Eatman Photo

A female Hoplitis mason bee 

All photos (c) 2014 - 2016 Sharp-Eatman Nature Photography

Hoplitis Mason Bees

Chelostoma Mason Bees

Mock Orange Chelostoma

Chelostoma philadelphi
Subgenus Prochelostoma

females:  1/4" - 3/10" - males:  1/5"  (small to very small)

Like Osmia and Hoplitis mason bees, Chelostoma belong to the tribe Osmini of the family Megachilidae.  And like females of those genera, Chelostoma carry pollen on scopal hairs under their abdomens.  


Chelostoma are solitary and build their individual nests in hollow stems and in pre-existing holes dug by beetles and other organisms.  The bees divide their nests into series of chambers, fashioning partitions between them from a cement-hard mixture of fine pebbles and plant resins.


There are nine native species of Chelostoma in North America, and only one in New York -- Chelostoma philadelphi, shown here.  This is a small, antlike bee that specializes in pollinating mock orange (Philadelphus), a flowering plant genus that includes several varieties native to the United States.  Mock orange plants have white flowers with bright yellow stamens and leaves which, when crushed, produce a strong citrus scent. Mock orange blossoms in Westchester County in the second week of June.  At Stone Barns, mock orange chelostoma arrive in large numbers to pollinate the flowers as soon as they open.  

Despite these mason bees' preference for mock orange, they do occasionally pollinate other flowers.  One of the bees shown here was found foraging on chamomile in the Dooryard Garden of Stone Barns, not far from a mock orange bush.  Mock orange chelostoma also have been documented feeding on salvia, lilacs, caneberries, geraniums, hawthorne, holly, waterleaf and members of the mustard family.

Identification information:

"Chelostoma" means "claw mouth".  As shown in the photo strip at right, bees of this genus have spectacular long jaws with ridged, toothed mandibles. Chelostoma mason bees have only two submarginal cells in their forewings, and their front feet sport an unusual extra part called an arolium.

Chelostoma philadelphi can be mistaken easily for small flies or winged ants -- they are black, long-bodied bees with large heads.  They are also miniscule and easily escape notice.  The best way to find these bees at work in nature is to watch mock orange shrubs during their blooming cycle.  

Female mock orange chelostoma have white scopal hairs under their abdomens (on the sternum).  The bees' undersides often appear to be bright yellow -- this is because the pollen of mock orange is an intense yellow.

Similar species:  Two invasive species of Chelostoma mason bees, originally from Europe, are found in New York:  C. campanularum and C. rapunculi. Both have somewhat smaller jaws than the mock orange chelostoma but are otherwise similar in appearance.  Nevertheless the invasive species can be fairly easily distinguished because they specialize on bellflowers.

Chelostoma philadelphi

A female Chelostoma philadelphi mason bee 

Chelostoma philadelphi - (c) 2017 Sharp-Eatman Photo

A female Chelostoma philadelphi mason bee 

All photos (c) 2014 - 2017 Sharp-Eatman Nature Photography

Heriades carinata Resin Bee

Heriades carinata

1/6" to 1/4"   (small)

Heriades variolosa /  leavitti Resin Bee

Heriades variloosa / leavitti

1/5"   (small)

Heriades resin bees are equiipped with mandibles designed to scrape resin from plants.   These native bees nest in pre-existing holes in wood and hollow stems, and they use plant resin to plug entrances to their egg chambers. 


The common name "resin bee" is also applied to other bee genera – for example, resin bees of the subgenus Megachile  (Cheolostomoides) are shown on this guide’s leafcutter bee page.  Heriades tend to be smaller than resin bees of the genus Megachile.  The two Heriades resin bees shown here, for example, are a mere 1/6 to 1/4 inch in length.

​​Like the Osmia, Hoplitis and Chelostoma mason bees shown in this guide's preceding sections, Heriades carry pollen on scopal hairs under their abdomens; and the bees' forewings have only two submarginal cells.

According to entomologist Charles D. Michener, defining traits of bees of the genus Heriades include the following:  (1) A ridge runs across the front top edge of the first segment of the bee's abdomen; and (2) the front face of the bee's abdomen is concave.​

Heriades of several subgenera are found throughout the world, but a single subgenus, Neotrypetes, occurs within North America, ranging from Canada to Panama. Heriades found in the United States are black with pale hair bands on their abdomens.  Coarse Indentations pit their heads, thoraxes and abdomens.  The scopal hairs on the female's sternum are usually white and often long and conspicuous even to the naked eye, despite this species' small size. ​

Male Heriades can be recognized by their abdomens, which curl under, the tips nearly touching the front segments.  On males, only S1 and S2 (the first two segments of the sternum) are generally visible when the bee is turned over. Viewed from above, the last segment of the male bee's abdomen (T7) is hidden by the sixth segment (T6).  

Heriades  tend to be generalist pollinators that forage on a range of flora.  In our area, they are commonly found on such plants as agastache, allium, butterfly weed, coreopsis, fleabane, goldenrod, marjoram, mountain mint, sumac, swamp milkweed, spreading dogbane, wild bergamot and members of the squash family.


There are at most three or four species of Heriades resin bees in the New York area.  The female bee shown here has been identified as belonging to one of two very similar resin bee species -- Heriades leavitti or Heriades variolosa. This resin bee was found foraging on orange butterfly weed (Asclepias tuberosa) in the VIsitor Center garden of Rockefeller State Park Preserve in early July, 2017.  


The second bee at right is a Heriades carinata.   This bee  has a keel-like structure, called a carina, on its mandibles. This trait is diagnostic of the species.  Heriades carinata do not emerge until the weather grows hot. These bees appear in the vegetable and cut-flower fields of Stone Barns Center for Food and Agriculture in August.


Heriades carinata are reported to be energetic pollinators of onions and  leeks. The Heriades carinata female shown here was found feeding on fringed quickweed, a plant of Mexican origin now naturalized in the United States and belonging to the aster family.  This naturalized weed self-seeds in Stone Barns' dahlia and strawflower beds. 




Family:  Megachilidae

Tribe:  Osmiini

Genus:  Heriades

Subgenus:  Neotrypetes
Species:  Heriades carinata

Heriades leavitti / variolosa Resin Bee - (c) 2017 Sharp-Eatman Photo

A female Heriades leavitti / variolosa

Heriades carinata Resin Bee - (c) 2015 Sharp-Eatman Photo

A female Heriades carinata resin bee

All photos (c) 2014 - 2016 Sharp-Eatman Nature Photography

Heriades Resin Bees

This website's photos and text are protected by registered copyright. All photos are © 2014-2024 Paula Sharp & Ross Eatman, all rights reserved.  To inquire about possible use of photos, see Permissions. 


REFERENCES:  For a comprehensive list of references used in compiling this guide, click here:

bottom of page