Canadian Journal of Arthropod Identification

Cleptoparasitic Bees of the Genus Epeolus Latreille (Hymenoptera: Apidae) in Canada

CJAI 30 -- March 30, 2017

Thomas M. Onuferko

| Abstract | Introduction | Methods | Taxonomy & Biology | Checklist | Keys to species | Acknowledgments | References | PDF | Cite |


As the sexes in this genus are for the most part monomorphic (other than for typical sexually dimorphic characters), a single identification key for adult Epeolus species in Canada is presented. The identification key is based on external morphological differences that should be visible in dry, pinned specimens. In addition, species redescriptions of the sex opposite that of the primary type include only the key differences between females and males.

To clarify species limits and to give additional support for new synonymies reported here, the divergence levels in a 658 bp segment of the COI mitochondrial gene (DNA barcode) (Hebert et al. 2003a, b) were used in conjunction with morphology. Barcoding entailed the removal of a leg (the source of genetic material) from a bee for DNA extraction and gene amplification and sequencing at the Canadian Centre for DNA Barcoding (CCDB) in Guelph, Ontario, Canada. Barcode Index Numbers (BINs – automated code numbers given to unique barcode clusters) were assigned to sequences as short as >300 bp, although formal recognition of barcode compliant sequences requires a minimum length of 500 bp (Ratnasingham and Hebert 2007, 2013). To validate species designations of specimens and to check for contamination errors, sequences with unique BINs were compared to one another and to short, non-compliant sequences that clustered with compliant ones in a neighbour-joining (NJ) tree, based on Kimura's two-parameter distance model (Kimura 1980). Cases involving change in taxonomic status always prioritized morphological evidence over DNA barcoding, and barcoding merely confirmed what was already suspected to be continuous intraspecific variation in morphology. BINs are available for all species recorded in Canada except E. ilicis and are provided in the taxonomic treatment for each species. Sequences for “barcoded” specimens are published in BOLD ( in the “Epeolus of North America” project, and will be made available on GenBank ( following a revision of all Nearctic Epeolus species north of Mexico.

Anatomical and taxonomic terms used generally follow Michener (2007), except I use the terms frontal and vertexal areas instead of frons and vertex, respectively, following Prentice (1998) and Dumesh and Packer (2013), as these are not clearly delimited structural features. Puncture density is quantified as the interspace (i) relative to the puncture diameter (d). MOD is an acronym for median ocellar diameter, used as a comparative measure for indicating the dimensions of smaller features, especially hair length. F with a number corresponds to one of 10 (for female) or 11 (for male) flagellomeres of the antenna. T with a number corresponds to one of six (for female) or seven (for male) exposed metasomal terga. S with a number corresponds to one of six (for female) or eight (for male) metasomal sterna. I use the term ferruginous to distinguish black or nearly black integument from that which is any of the following colours: light brown, mahogany, reddish brown, red, and rusty orange. All measurements comparing lengths and widths are based on the longest and widest margins of an anatomical feature of a specimen at the highest magnification that would allow measurement in eyepiece micrometer units. I use the term length to describe any measurement along the longitudinal axis of a bee, and width to describe any measurement along the lateral axis, except in reference to the longitudinal extent of the transverse metasomal fasciae, for which I use the term breadth. Measurements of the scape were made excluding the radicle. Rightmyer (2008) proposed several terms specific to epeoline/nomadine bees, which I have adopted (with exceptions) and redefine here for clarity. Paramedian bands are the two longitudinal anterior lines of pale tomentum (pubescence composed of short, matted hairs) on the mesoscutum (extending posteriorly from the anterior margin of the mesoscutum but not attaining its apex) found in most Epeolus species. In E. canadensis and E. compactus I do not consider as paramedian bands the anteromedial patch of pale tomentum barely separated by the admedian line. The transverse bands of Rightmyer (2008) I refer to as the basal and apical metasomal fasciae. The fasciae of T1 may be connected laterally by a longitudinal band of varying width. Discal patch refers to the dark medial region of T1 covered in brown to black tomentum that may be sparser than the off-white or yellow tomentum forming the basal and apical (when present) fasciae.

Redescriptions are based on primary type specimens, although other specimens (usually non-type sequenced) were referenced for comparison and to fill in information gaps. The description of the sex opposite that of the primary type was based on the allotype or lectoallotype specimen (if available), paratypes, or non-type specimens. Specimens for study were provided by entomological institutions, museums, and university collections across Canada and the United States of America (USA), and are indicated with the following acronyms, with full names provided in parentheses: AMNH (American Museum of Natural History, New York, NY), ANSP (Academy of Natural Sciences of Drexel University, Philadelphia, PA), BBSL (Utah State University USDA Bee Biology and Systematics Laboratory, Logan, UT), BIML (Patuxent Wildlife Research Center USGS Native Bee Inventory and Monitoring Lab, Laurel, MD), CAS (California Academy of Sciences, San Francisco, CA), CNC (Canadian National Collection of Insects, Arachnids and Nematodes, Ottawa, ON), CTMI (Central Texas Melittological Institute, Austin, TX), CUIC (Cornell University Insect Collection, Ithaca, NY), DEBU (University of Guelph Insect Collection, Guelph, ON), EMEC (University of California Essig Museum of Entomology, Berkeley, CA), FMNH (Field Museum of Natural History, Chicago, IL), FSCA (Florida State Collection of Arthropods, Gainesville, FL), INHS (Illinois Natural History Survey, Champaign, IL), KUNHM (University of Kansas Biodiversity Institute and Natural History Museum, Lawrence, KS), NCSU (North Carolina State University Insect Museum, Raleigh, NC), PCYU (Packer Collection at York University, Toronto, ON), ROM (Royal Ontario Museum, Toronto, ON), RSKM (Royal Saskatchewan Museum, Regina, SK), UCR (University of California Entomology Research Museum, Riverside, CA), and USNM (U.S. National Entomological Collection, National Museum of Natural History, Washington, D.C.).

In lists of specimens examined, the records from different localities are always separated with a semi-colon. A comma between records denotes that the collection locality is the same but at least one of the following is different: date, collector, and entomological institution. With regard to specimen occurrence records, there were instances in which locality data were rather vague, particularly true of older records, and localities straddled county lines. In such cases, I omitted the county name and indicated the contents of the specimen labels. The same was true if I was unable to pinpoint an indicated locality on a Google map.

The key and redescriptions are accompanied by images taken with a Canon EOS 40D digital SLR camera using the Visionary Digital BK Plus imaging system, focus stacked in Helicon Focus, and edited in PaintShop Pro. In preparation for study and imaging, terminalia were excised, cleared in KOH for up to six hours, and ultimately stored in glycerine, later transferred to genitalia vials pinned under the associated specimens.

Range maps were constructed in RStudio (version 0.97.248) using the following packages installed in R (version 2.15.0): maptools (Bivand and Lewin-Koh 2014), raster (Hijmans 2014), rgdal (Bivand et al. 2014), and rgeos (Bivand and Rundel 2014). Maps of Canada and the USA were plotted using projected shapefiles obtained from Statistics Canada (2015) and the U.S. Census Bureau (2015). Points of occurrence for a particular species are based on GPS coordinates accurate to at least two decimal degrees. Using customized functions in R, continuous ranges were estimated by forming a splined convex hull polygon, a method also used for preparing distribution maps for the International Union for Conservation of Nature (IUCN 2012), of georeferenced occurrence records (from the literature and observed voucher specimens).