Bees of the Genus Dufourea Lepeletier (Hymenoptera: Halictidae: Rophitinae) of Canada*
CJAI 20 May XX, 2012
doi:10.3752/cjai.2012.20

Sheila Dumesh1**, Corey S. Sheffield2

1Department of Biology, York University 4700 Keele St., Toronto, ON M3J 1P3 mexalictus@ymail.com
2Royal Saskatchewan Museum, 2445 Albert Street, Regina, SK S4P 4W7 cory.silas.sheffield@gmail.com

* This paper is contribution #13 from the Canadian Pollination Initiative. **Corresponding Author.

Abstract | Introduction | Key to Genera | Species | Acknowledgements | References | PDF | Cite this Article

Introduction
          Rophitine bees (Rophitinae) are a relatively small (214 species, as per Michener (2007); 257 species listed by Ascher and Pickering (2012)), basal subfamily of the Halictidae (Pesenko 1999) containing four tribes: the Rophitini (Old and New World members), Penapini (South America), Conanthalictini and Xeralictini (both restricted to south-western North America) (Patiny et al. 2007).  The Rophitinae are primarily Holarctic in distribution (Michener 1965; Rozen 1997; Niu et al. 2005) with about a dozen species occurring in the Southern Hemisphere: five in South America (Rozen 1997) and six or seven in Africa (Patiny and Michez 2006, 2007a, 2007b).  Rophitinae is the only subfamily of Halictidae in which all members are solitary (Pesenko and Astafurova 2006; Patiny et al. 2007; Danforth et al. 2008; Richards and Packer 2010).  Despite the paucity of species in the Southern Hemisphere, Patiny et al. (2007) suggest that the strictly South American tribe Penapini forms the sister group to the remaining Northern Hemisphere tribes, with all the Old World taxa having arisen from among the New World Rophitini.  The genus Dufourea Lepeletier in North America represents a dispersal event back from the Old World (Patiny et al. 2007).  As such, it is the only holarctic genus of Rophitinae (Michener 1965), and also the only one occurring in Canada.
Disagreements in higher level classification exist within the Rophitinae, particularly between classifications used in the Old and New World.  For instance, Niu et al. (2005) and Pesenko and Astafurova (2006) recognize 16 genera of Rophitinae, while Michener (2007) and Patiny et al. (2007) recognize 13, the latter two studies maintain Trilia Vachal as a subgenus of Dufourea, and Rhopitoides Schenck as a subgenus of Rophites Spinola, and place Flavodufourea Ebmer as a subgenus of Rophites Spinola.  Although Flavodufourea was originally described as a subgenus of Dufourea, a position supported by Patiny (2003), Michener (2007) believes its placement is still not decisive.  Michener (2007) also does not recognize subgenera within Dufourea.
Six genera of Rophitinae occur in North America (Michener 2007).  The largest genus is Dufourea (ca. 70 species), followed by Conanthalictus Cockerell (13 species), Micralictoides Timberlake (8 species), Protodufourea Timberlake (5 species), Sphecodosoma Crawford (3 species), and Xeralictus Cockerell (2 species).  Michener (1965) reviewed the Rophitinae of the Western Hemishpere; Snelling and Stage (1995) clarified the placement of the Xeralictini within the Rophitinae.
Dufourea are relatively uncommon bees in Canada, and no comprehensive account of the species has been published.  Morphologically, Dufourea is distinctive among the Canadian bee fauna, having antennae that arise low on the face, usually just above the upper margin of the clypeus.  Dufourea differs from other non-cleptoparasitic Halictidae in Canada in having the scopa restricted to the hind tibia (not present also on the hind femur as in other halictids), and in having a short clypeus which seldom is any longer than the labrum (Michener 1965).  Dufourea is also the only genus of Halictidae in Canada with two submarginal cells (the exceptions being a few species of Lasioglossum (Dialictus) and Sphecodes).  Keys in Mitchell (1960), Stephen et al. (1969); Michener et al. (1994), and Michener (2000; 2007) can be used to identify this genus in North America; Packer et al. (2007) provide an interactive web-based key for bee genera in eastern Canada.  Mitchell (1960) published keys to the four species found in the eastern Canada.
All Rophitinae, including Dufourea, nest in soil (Pesenko and Astafurova 2006), and construct a single nesting tunnel with lateral burrows which end in single cells, or a series of multiple cells (Michener 2007).  Rozen and McGinley (1976), Kukuk et al. (1985), and Rozen (1993) summarize the nesting biology of Rophitinae.  The nesting biology of three of the eight Canadian Dufourea have previously been studied: D. trochantera Bohart (Torchio et al. 1967); D. novaeangliae (Robertson) (Eickwort et al. 1983), D. holocyanea (Cockerell), including the description of the mature larvae (Rozen and Ozbek (2008).
Dufourea species are well known for their floral specialization (Lincoln 1981; Patiny et al. 2008).  Floral specialization has lead to morphological adaptations in many bees, including Dufourea; Alves-dos-Santos (2003) found that mouthparts of bees specializing on Pontederiaceae, including D. novaeangliae, are covered with hairs to remove pollen from the concealed anthers.  Each species of Dufourea in Canada specializes on a different plant family (Table 1).  Although Lincoln (1981) reported D. dilatipes Bohart on both Calochortus (Liliaceae) and Campanula (Campanulaceae) in Canada, it seems the latter floral record may actually be based on misidentification of specimens of D. maura (Cresson) as one of the two pollen samples examined was from Ontario (see Lincoln 1981), far outside the known range of D. dilatipes (Plate 1, Figure E).  Calochortus has a Canadian distribution restricted to southern AB and BC; only one species, C. apiculatus, is recorded from Waterton Lakes National Park, one of only a few known collections site of D. dilatipes in Canada (and one of the localities for the type series).  Most of the other species of Dufourea in Canada are also found in the west; D. holocyanea occurs in southern BC (Plate 3, Figure E), and D. trochantera occurs in BC and AB (Plate 8, Figure E).  Dufourea fimbriata (Cresson) has only been collected a few times in Canada, in AB (Edmonton), in NT (Yellowknife), the most northern record for this genus in North America, and in northern ON (Plate 2, Figure E).  Dufourea maura is the most widespread species, occurring from southern BC to ON (Plate 5, Figure E).  Dufourea marginata (Cresson) is also widespread in Canada, occurring in southern BC-ON.  Two species, D. monardae (Cresson) and D. novaeangliae occur in eastern Canada; D. monardae is known only from southern ON (Richards et al. 2011) (Plate 6, Figure E) and the adjacent United States (Bouseman 1976), D. novaeangliae has been collected in ON, QC (Payette 2001) and NS (Sheffield et al. 2003) (Plate 7, Figure E).
Our objectives are to provide an illustrated key to the eight species of Dufourea occurring in Canada, full species descriptions, images of male genitalia, distributional notes, and a general summary of floral relations.


Materials and Methods

Specimens examined were from the following institutions: Canada: Packer Collection York University, Toronto, ON; Canadian National Collection of Insects, Arachnids and Nematodes, Ottawa, ON; Royal British Columbia Museum, Victoria, BC; Beaty Biodiversity Museum, University of British Columbia, Vancouver, BC; Royal Alberta Museum, Edmonton, AB; E.H. Strickland Entomological Museum, University of Alberta, Edmonton, AB; Brock University, St. Catharines, ON; Wallis-Roughley Museum of Entomology (formerly J.B. Wallis Museum), University of Manitoba, Winnipeg, MB; United States: United States Department of Agriculture Bee Biology and Systematics Laboratory, Logan, Utah; KU Biodiversity Institute, University of Kansas, Lawrence, Kansas.
Terminology used for the species descriptions includes: pd (puncture diameter); MOD (median ocellar diameter); IAD (interantennal distance); AOD (antennal-ocular distance); OVD ([median] ocellar-vertexal distance); OOD (ocellar-ocular distance); IOD (inter-ocellar distance); Tx (tergum x); Sx (sternum x).
Head breadth was measured as the greatest distance between outer most margins of compound eyes; head length was measured as the distance from the apex of the clypeus to the summit of the vertexal area.  In the descriptions, head breadth to length is given as a ratio (b:l).
Images were taken using a Visionary Digital BK Plus imaging system using a Canon EOS 40D digital SLR camera and processed with Adobe Photoshop.

 

Table 1.  Floral hosts of Dufourea (Halictidae) species occurring in Canada.

Dufourea species

Floral Host Floral Host Family Reference
D. dilatipes Calochortus Liliaceae Lincoln 1981
D. fimbriata Potentilla Rosaceae Lincoln 1981
D. holocyanea Symphoricarpos Caprifoliaceae Lincoln 1981
D. maura Campanula Campanulaceae Lincoln 1981
D. marginata Helianthus Compositae Lincoln 1981
D. trochantera Phacelia Hydrophyllaceae Lincoln 1981
D. novaeangliae Pontedereria Pontederiaceae Bouseman 1986
D. monardae Monarda Labiatae Bouseman 1976