Megachilidae

1
Megachilidae

• Chunky Bees that Carry Pollen Under their
  Abdomens
• A Guide to their identification in Eastern North
  America

2
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_at_usgs.gov

3
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

4
Meg Genera

• 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

5
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

6
Anthidiellum
2 Species, small, fast, likes legumes and dry
sites
7
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

8
Anthidium
4 Species
Some common introduced species
9
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

10
Dianthidium
3 Species
Uncommon to rare
11
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

12
Paranthidium jugatorium
Uncommon, garden exception
13
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

14
Stelis
Uncommon, parasites of Hoplitis, Osmia, Heriades,
Ashmeadiella
12 Species
15
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

16
Trachusa
Uncommon, southern, 5 species
17
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

18
Hoplitis
Relatively common 8 species
19
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

20
Osmia
Common, spring, hole-nester, 28 species
21
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

22
Ashmeadiella
Rare Small 2 species
23
Chelostoma

• Rare 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

24
Chelostoma
Tiny, elongate, 3 species, 2 introduced
25
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

26
Heriades
Tiny, uncommon to locally common, 3 species
27
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

28
Megachile
Common in all open environments 40 species
29
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

30
Coelioxys
Parasite of Megachile, pointed rear, arolia, no
scopa 24 Species
31
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

32
Lithurgus
Rare, 2 cactus specialists, 1 introduced
33
Resources

• Species lists, Identification Guides, and Maps
  for genera and species are available at
• http//www.discoverlife.org/20/q?searchApoidea
• 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
• Mitchells 1960s 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?
  ScreenPRODStore_CodeKCNPProduct_CodeBGNACate
  gory_CodeBL