identification guide to the megachilidae genera of eastern north america

Chunky Bees that Carry Pollen Under their Abdomens:

A Guide to their identification in Eastern North America

Acknowledgements

• This presentation has been put together by a consortium of North American bee biologists

• This presentation has developed over many years and the original web picture acknowledgements were lost, if you see one of your pictures let us know and we will add your picture credit

• Correspondence can be sent to Sam Droege at sdroege@usgs.gov

Format

• Each Genus has an information page followed by a page of illustrations and a map of the distribution of Eastern North American species; western populations of Eastern species are shown, but the Western species are not mapped.

• The number of Eastern species are listed at the top of the page

Anthidiellum – 2 species

Anthidium - 4 Dianthidium - 3 Paranthidium -

1 Stelis - 12 Trachusa - 5

Hoplitis - 8 Osmia - 28

Ashmeadiella - 2

Chelostoma - 3 Heriades - 3

Coelioxys - 24 Lithurgus - 3 Megachile - 40

Anthidiellum

Quite small, less than half the size of a honeybee Fast flying, likes legumes, dry fields Front of the mesepisternum (side facing the

head) divided from the outward facing side by a sharp edge or carina

Unique in that the scutellum projects over the metanotum and propodeum as a THIN squared- off shelf, other species project a small amount but not as much and the edge is rounded over

Unique in that the sub-antennal sutures bend outwards

Similar Genera: Anthidium, Dianthidium, Paranthidium, Stelis, Trachusa

2 Species, small, fast, likes legumes and dry

sites

Anthidium 2 common introduced species, 2 rare

native species, most about the size of a honeybee or slightly smaller

Unique among genera listed below in that it has no pad or arolium between the tarsal claws at the ends of the legs

Female unique in that it has 5 or more teeth on the mandible

Similar Genera: Anthidiellum, Dianthidium, Stelis, Trachusa, Paranthidium

Some common introduced species

4 Species

Dianthidium A bit smaller than a honey bee,

uncommon to rare Has a small hollowed out area or fovea

behind the spiracle on the rear face of the propodeum about the size of the spiracle

Front of the mesepisternum (side facing the head) divided from the outward facing side by a sharp edge or carina

Similar Genera: Anthidium, Paranthidium, Stelis, Anthidiellum, Trachusa

Uncommon to rare

3 Species

Paranthidium jugatorium Rare, but known to occur abundantly in at least

one arboretum Front of the mesepisternum (side facing the the

head) NOT divided from the outer facing side by a sharp edge or carina

Front and middle tibia without a spine, the outer tip of tibia with a curved, transverse, projecting lamella, behind which the surface is shining and scoop-like

Margin of tip of mandible straight and at an oblique angle to outer margin, about half as long as mandible

Similar Genera: Anthidium, Anthidiellum, Dianthidium, Stelis, Trachusa

Uncommon, garden exception

Stelis Rare, one quarter to two-thirds the size of the

honeybee Nest parasites on Osmia, Megachile, Heriades,

and Ashmeadiella and thus have no scopa on the underside of their abdomens like most other Megachilidae species

A variety of body types from very bright and colorful like Anthidium to dark and small like Heriades, some of these groups have been assigned Genus status in the past

Similar Genera: Trachusa, Anthidium, Anthidiellum, Dianthidium, Paranthidium, Heriades, Ashmeadiella, Chelostoma

Uncommon, parasites of Hoplitis, Osmia, Heriades, Ashmeadiella

12 Species

Trachusa Uncommon to rare, about the size of a

honeybee Front edge of scutum clearly raised

above the pronotal collar Similar Genera: Stelis, Anthidium,

Anthidiellum, Paranthidium, Dianthidium

Uncommon, southern, 5 species

Hoplitis Relatively common dark brown, spring

to early summer species Parapsidial line on scutum long and

similar to most other bee species Males often have modified antennae

with hooked ends or expanded segments

Similar Genera: Osmia, Heriades, Chelostoma, Ashmeadiella

Relatively common

8 species

Osmia Common spring to early summer species,

ranging from one-third the size of a honeybee to slightly larger

The majority of species are dark blue (often appearing black in the field) with a few that are brown, black, and one rare bright green one

The parapsidial line of the scutum contracted to a line that is usually only 2-5 pit diameters long and is often difficult to find amidst the surface pitting

Differentiating males is particularly tricky as many of the best characters are on the underside of the abdomen and often hidden by retracted segments and curled abdomens

Similar Genera: Hoplitis, Ashmeadiella, Heriades, Chelostoma

Common, spring, hole-nester, 28

species

Ashmeadiella Rare, about one quarter the size of a

honeybee Front of the mesepisternum (side facing

the head) divided from the outer facing side by a sharp edge or carina

Similar Genera: Heriades, Chelostoma, Stelis, Osmia, Hoplitis

Rare

Small

2 species

ChelostomaRare to Locally Common, Small, about

one-quarter the size of a honeybee Skinnier and more elongate than the

other Megachilid genera Head unusually long 2 introduced species now spreading

slowly from New York and Ontario and pollen specialists on Campanula, 1 native species which is a specialist on Mock Orange (Philadelphus)

Similar Species: Heriades, Ashmeadiella, Osmia, Hoplitis, Stelis

Tiny, elongate, 3 species, 2 introduced

Heriades Uncommon, small, about one quarter the size of

a honeybee Has a very sculptured appearance with large

diameter pits throughout Upper surface of Propodeum is formed of a

narrow row of open square cells defined by prominent raised lines

Unique within Megachilidae in that the portion of T1 that faces the thorax is hollowed out and surrounded by a raised line or carina

Similar Genera: Ashmeadiella, Chelostoma, Hoplitis, Osmia, Stelis

Tiny, uncommon to locally common, 3 species

Megachile Moderate to large, common particularly in the

summer, from about half to 1.5 times the size of a honeybee

Most are black with thin white bands of hair on their abdomens

Males of some species have greatly expanded front tibia

Cutting edges of the mandibles often very useful in females but best seen by pulling open mandibles when specimens are fresh

Unlike genera listed below, has no arolium or pad between the tarsal claws of the legs

Similar Genera: Lithurgus, Coelioxys

Common in all open environments

40 species

Coelioxys Regular, but sparsely distributed, primarily out in

the summer and early fall, most about the size of a honeybee

Nest parasites of Megachile and thus the females have no pollen carrying hairs under their abdomens

The axillae, which normally hug the edge of the scutellum, flare outwards and the shape of their tips are often diagnostic

Females have long, pointed abdomens, the shape of which is often unique

Males have an odd cluster of pointed or flattened projections and spines at the end of their abdomen, the pattern of which is also often unique

Similar Genera: Megachile, Lithurgus

Parasite of Megachile, pointed

rear, arolia, no scopa

24 Species

Lithurgus Rare to locally common 2 native species are cactus (Opuntia) pollen

specialists The introduced species, L. chrysurus, is spreading

slowly out of central New Jersey and eastern Pennsylvania and is a knapweed (Centaurea) pollen specialist and can be abundant when found

Often overlooked as Megachile (particularly males) but has an arolium or pad between its tarsal claws

Females all have a diagnostic and very prominent projecting flange between the clypeus and the antennal bases

Both males and females have a 3-lobed tip to the mandible

Rare, 2 cactus specialists, 1 introduced

Resources

Species lists, Identification Guides, and Maps for genera and species are available at:

http://www.discoverlife.org/20/q?search=Apoidea A guide to the genera of the bees of Canada is available

at:http://www.biology.ualberta.ca/bsc/ejournal/pgs_03/pgs_03.html Mitchell’s 1960’s book on the bees of the Eastern United

States is available as a series of pdf files at:http://insectmuseum.org/easternBees.php A slightly out of date guide to the identification of the

genera of ALL of North America is available at:http://www.knoxcellars.com/Merchant5/merchant.mvc?

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