Osmia: Select species diagnoses

About this resource

aglaia (CA)
albolateralis (OR)
atriventris (MI,MD)
atrocyanea (OR)
cf. caerulescens (OR)
calla (CA)
cara (CA)

cornifrons (MI)
cf. cyanella (OR)
densa (OR)
exigua (CA)
georgica (PA)

lignaria (OR,MI)
nemoris (OR)
not Osmia (OR)
pumila (MI)
sculleni (OR)
taurus (VA)
virga (PA)

Click any image for a larger magnification.

Osmia aglaia

I don't have specimens in hand, so can only evaluate what is discernible in photos; these are inadequate to get close to a diagnosis.

Evident in photos:

9mm, California;
Brilliant metallic/violaceous coloration;
Clypeus darker apically, margin straight;
Clypeal hairs dark (at least for USGS photo);
Hind tibia and femur with equal metallic color;
Scutm hairs mixed pale/dark;
Scopa dark;
T2 unpitted band moderately long.

Initial result in DL guide:

Osmia aglaia
O. bruneri
O. ednae

So, close to the correct answer? Yes, but beware confirmation bias. Problems ... DL excludes O. aglaia when when I add "unpitted rim of clypeus short, less than 2 pit diameters long." But this condition is evident (to me) in the photos. In any case, Sandhouse states: "Impunc tate band of clypeus rather narrow."

I conclude that DL cannot differentiate the three species, and I question whether the specimen is even one of these; the photos offer inadequate evidence to go further.

Images above and right, of specimens from Loren Ponisio's Lab at University of Oregon.

Images this row: USGS Bee Lab, photograph by Anders Croft. "from Yosemite National Park , where Claire Kremen's group has been looking at post burn bee communities in areas of chronic burns. "

Osmia albolateralis

Another example for which I have only standard images, from the USGS Bee Lab, and Laurence Packer. These don't provide enough to support a diagnosis, so I defer to the IDs given with the photos. I note that like for O. aglaia, DL scores O. albolateralis as having a clypeus rim with a long unpitted band; I don't see that here.

USGS Bee Lab image, Elizabeth Garcia, CA specimen/

Image above: O. albolateralis, from Bees of Canada, Packer Lab.

Above: USGS Bee lab image, Elizabeth Garcia, specimen from WY.
Below: CA specimen.

Osmia cf. atriventris

Easy calls:

8mm;

T2: unpitted band a few pit diameters wide and strongly defined;

Clypeus with long pale hairs, edge not swollen;
Dull metallic integument;
Vertex ~2 od;
Clypeus rim concave, 2 tufts of bristles;
Clypeus, scutum, and T5 hairs light, scopa black;
Mandible polygonal, ridges converging, lower ridge thicker;

Initial result in DL guide:

Osmia glauca
O. virga
O. atriventris

Specimens here vs O. virga: Unpitted band on T2 clypeus shorter (25% for O. virga); mandible polygonal (rectangular for O. virga). Specimen here vs O. glauca: all from eastern US (O. glauca western US).

Image above: Michigan specimen.
Below: O. atriventris from West Virginia, Bees of Canada, Packer Lab.

From Rightmyer key: "malus with pointed apical tip" (vs malus truncate for O. virga); Sandhouse says of O. virga: "Spine at apex of strigilis extremely short" )

Pale tergal hairs; moderately long T2 unpitted band.

Mandibular carinae converge apically; lower carina thicker.

From penultimate couplet in Rightmyer key: "Clypeus with apical margin forming two distinct carinae on either side of two apical tufts of hairs." By contrast, many other Osmia have an impunctate clypeal apex, but in this case the apex is upturned to form a carina.

Osmia atrocyanea

I start with the tentative determnination, from photos, by Molly Rightmyer. The key evidence: blunt "singed" hairs of fore basitarsus. In the DiscoverLife guide, using unambiguous traits, I get 4 alternatives. Not O. bella or O. tristella, which are smaller (8-9mm). O. bruneri and O. cobaltina probably have more distinctly brilliant integument. DL rejects O. cyanella which would have a carinate vertex posteriorially. I reject O. calla, which also has singe-haired foretarsi, as too small (8mm).

Specimens from sites near Corvallis, OR. Hairs and scopa all black, or with sparse light hairs dorsally, as in bottom image. Size 12-13mm

Osmia cf. caerulescens

This specimen is from the Willamette Valley, collected from Lupine. DiscoverLife, ID attempt: Features visible in photos: Head exceptionally large; Tergal hair bands; Pits nearly to edge on T2, T3; Clypeus edge straight; Apical edge of clypeus with pits near edge; Scutum, episternum hairs pale; Scopa black; Mandible: 1st and 2nd tooth closer than second and fourth; Upper margin of lower tooth 1.7X lower margin of second; No carina at base of cutting edge; Cutting edge not recessed; Mandibular ridges parallel; These traits yield O. nemoris and O. caerulescens. The lack of spatulate tarsal hairs would leave O. carulescens as the choice. However: This species should have clypeal bristles in "four distinct tufts - often one pair of tufts is on the outer surface of the clypeus in addition to beneath the rim of the clypeus." I don't see that here.	ID attempt in the Mitchell key: I need only specify: no malar space; no inferior mandibular tooth; mandibles simple; tergal apical fasiciae. This yields O. caerulescens, the blue mason bee. There are manyfield photos of O. caerulescens here. Text on the page states: "Females of this medium-sized mason bee are fairly distinctive with their oversized, box-shaped head (almost as big as the thorax)."	ID attempt in Rightmyer key: The first step is to assign subgenus. If I could convince myself that my specimen is Helicosmia (=Chalcosmia), that subgenus key gets me straightforwardly to O. caerulescens--the first couplet. But I have the problem that I had in DL ... Helicosmia have "hairs just beneath apical margin of clypeus arranged into four distinct tufts (two smaller, median tufts and two larger" and "mandible with dense, appressed, orange hairs on outer surface just basal to teeth" (evident in mandible photo of O. georgica, a Helicosmia species). The actual ID: I suspect that there are any number of experienced taxonomists that would look at the lateral photo and instantly recognize this bee.
I don't have a slam-dunk ID for this specimen. But I have a lot of images. Above: Oregon specimen. Huge head, hair bands. All light hairs, black scopa. Below: O. caerulescens, from Bees of Canada, Packer Lab.	Scutum, left side.	Definite hair bands. Pits to edge of T2, T3. Above - hypostoma, Below - lateral view of hypostomal carina (mandible left). Mesepisternum

Osmia calla

Another Ponisio lab specimen for which I have only photos. I assume that this IS O. calla, given the T. Griswold ID.

The outstanding feature here is the brilliantly metallic and violaceous coloration. Other traits I can give DL enter into DL:

Integument brilliantly metallic ;
Scopal and clypeal hairs dark;
Moderately long T2 band;
Vertex less than 2 ocellar diameters;
Episternal pits sparser anterodorsally than medially;
Episternal pits shallower ventrally.

Initial result in DL guide:

Osmia exigua
O. calla
O. basillissa
O. bella

The photos don't provide useful evidence to differentiatte further. The singed forebasitarsal hairs (like atrocyanea, above) would be an important clue; not enough magnification here to discern this. The bottom line: this is O. calla mainly because T. Griswold would know.

California specimen, Griswold determination.

Image above: O. calla, from Bees of Canada, Packer Lab.

Osmia cara

I don't possess the specimen in these photos (another one in Lauren Ponisio's lab at University of Oregon), so I can't examine enough traits to make a diagnosis. However I assume that this IS O. cara, given the T. Griswold ID.

What I can see with some certainty, and enter into DL:

Distance between eyes equal above and below;
Gena less than twice eye width;
Scopa, episternum, scutum hairs dark;
Mandibular ridges equally thick and parallel;
Middle tooth closer to bottom than top tooth

Initial result in DL guide:

Osmia californica
O. cara
O. gabrielis
O. ribifloris

With the traits in DL, I can't confidently separate these based on the photos (but see tergite pic at right). The Sandhouse description includes: very thick median tuncation of the clypeus, with the transverse carina in middle. I don't discern that in the photo, but the lack of this condition would rule out O. gabrielis and O. californica in DL. The bottom line: this is O. cara mainly because T. Griswold would know. Note: The Washington Bee Atlas ID'd O. cara, a rare find in the state, photo here.

California specimen, Griswold determination.

"Clypeus rim extremely swollen, similar to that of O. bucephala." I don't see this.

"T2 integument near posterior rim very dull, covered with tiny shallow pits." Not exactly how I would describe this, but a row of smaller shallow pits is evident.

Osmia cornifrons

The female is unmistakeable: yellowish hairs, and 2 extremely large, obvious horns projecting at right angles to the plane of the clypeus at the outside edge. O. cornifrons bears a medial clypeal projections, unlike the similar O. taurus (DiscoverLife). The clypeal edge separates O. cornifrons from O. tauraus - not evident in the photos here. The male specimen here has dark integument and elongate middle flagellar segments. In DL, the choices are O. taurus and O. cornifrons. O. taurus would have more pronounced orange hair color.

Osmia cf. cyanella

This specimen is from the Browder Ridge in the Oregon Cascades.

For traits noted in photo captions, the list in DL:

Osmia cyanella
O. enixa
O. grinedeliae
O. inurbana

DL cannot narrow this further. In Sandhouse, I tentatively rule out O. enixa, which would have "all creamy or yellow" scutal hairs an acutely pointed strigilis spine, and lower mandible thicker than upper. O. inurbana is a challenge, as only the male is described in Sandhouse. In the Rightmyer draft key, O. inurbana would have a medial clypeal notch, as in this USGS/BIML photo of O. urbana. This specimen does not have a distinct notch. O. grindeliae does not appear in Sandhouse or the Rightmyer key, but someone knows how to ID it; there are 160 records in the Bee Library.

Image above: O. cyanella, from Bees of Canada, Packer Lab.

Mandible of specimen at right. Polygonal; Apex 1.5X wider than narrowest width; Carinae thin and parallel; middle tooth equidistant from 1st and 4th; cutting edge short, recessed; upper margin of 1st tooth 1.3X lower margin of 2nd.

Gena 1.3X eye width;

Vertex=2.6 od; T2 pits ~2 diameters from edge; scopa, scutum, episternum hairs dark.

Could this be O. cyanella? From Sandhouse: "The female can be distinguished from others of similar size and color by its short and wide head with the posterior margin of the vertex strongly concave." The head of this specimen is indeed short and wide; the vertex might be concave from a slightly different angle, but I'll never know, having sacrificed the specimen to obtain the mandible.

The hypostomal carina is difficult to photograph, and to interpret. In Sandhouse, O. cyanella has the carina "highest at the angle."

Osmia cf. cyanella?

This specimen is from the Oregon Cascades, collected from the same site, same day as the O. cf. cyanella above. It is a visually similar Melanosmia. So it is tempting to assume it is the same species. Is it?

Differences: dark scutal hairs dark mixed with light; T2 apical area longer and border less defined; head taller. The mandible is comparable, but differs in a couple of respects: 3rd tooth incomplete, and carina between 2nd and 4th teeth is well defined.

Polygonal; Apex 1.5X wider than narrowest width; Carinae parallel; middle tooth equidistant from 1st and 4th; cutting edge short, recessed; upper margin of 1st tooth 1.6X lower margin of 2nd.

Impunctate T2 apex long, with stray pits.

A taller head, and vertex convex.

Ventral and lateral view of hypostoma.

Osmia densa

The distinctive feature here: inwardly curving hypostomal hairs. In the DL Guide, this narrows choices to O. densa and O. glauca. The basket-like hypostomal hairs of the 2 species is given as an example of parallelism between the sugenera Melanosmia (densa) and Euthosmia (glauca). The latter has all pale clypeal hairs, and the Euthosmia condition of white scopa; the specimens pictured here have dark/light clypeal hairs and dark scopa. Incidentally ... I find no diagnosis for O. glauca.

The best evidence I have is the CA specimen, with a determination by Terry Griswold, who would know. My own specimen is a match, though I can't directly compare to the CA specimen, which is in Loren Ponisio's lab at U of OR.

Specimen from Groundhog Mtn, Oregon Cascades.

Osmia exigua

I only have images, photographed in Loren Ponisio's lab at University of Oregon. There is not enough info here to diagnose, but the ID by T. Griswold is authoritative.

BTW ... Sandhouse spells it exigua. Rightmyer and DL use exiguua, which is to me unpronounceable, but probably correct.

Image below: O. exigua, from Bees of Canada, Packer Lab.

Osmia georgica (Maryland) - USGS/BIML

The orange-ish scopa narrows the choices in DL to 15; it further narrows to 9 with pale hairs on scutum, clypeus, episternum, and T5. Then to 3 if we add a long (>3 od) vertex and T2 with pits out to the edge. O. foxi and O. coloradensis are western, ,so this eastern specimen is O. georgica.

Of course the obvious feature of this species is the "Mandible with large dorsal projection extending above apical margin of clypeus" (Rightmyer key).

Osmia lignaria

Females: in Discoverlife, only 3 species match: "2 extremely large, obvious horns projecting at right angles to the plane of the clypeus at the outside edge." Add one more trait - "mesepisternal hairs dark," and you have O. lignaria.

Female O. lignaria, Willanette Valley, OR

Male O. lignaria, MI

Osmia nemoris

There is a story for this species - see Osmia out of nowhere. Linc Best of Oregon Bee Atlas ID'd the specimens imaged here. To my knowledge, O. nemoris is unique in having the posterior lobes of smaller tarsal segments expanded into spatulate lobes (DiscoverLife) (photo lower right).

Osmia ... not

The specimen certainly looked like Osmia. I could have attempted to key it out, but luckily noted the linear parapsidal line. So, a metallic Hoplitis, not Osmia.