The 24 described and two undescribed species of Laphria Meigen (Diptera: Asilidae) currently known from eastern Canada (defined here as Manitoba eastward) and the adjacent United States are reviewed and keyed, with an emphasis on the Ontario fauna. Species in the related genera Dasylechia Williston and Lampria Macquart found in the same region are also keyed. Laphria cinerea (Back) and Laphria canis disparella Banks are recorded from Ontario for the first time. The female of Laphria sicula McAtee is included in a key for the first time.

Laphria posticata Say (photo by Stephen A. Marshall)

Laphria, broadly defined, is among the most easily recognized genera of flies in northeastern North America. Although they range in body length from 7.7 to 40.0 mm, most Laphria species are relatively robust and distinctively coloured bee-like or wasp-like flies. Laphria and the related genus Lampria can be further distinguished from other northeastern robber flies by the blade-like, laterally compressed proboscis that characterizes all North American members of the tribe Laphriini (as defined by Bullington 2016). Dasylechia belongs to the tribe Dasylechiini (Fisher and Wilcox, 1997), but was included in the key as it is superficially similar to Laphria species. As discussed below, we treat all eastern Canadian Laphriini other than Lampria bicolor (Wiedemann) as part of the genus Laphria. Further traits that characterize Laphria include a hind femur without tubercles, an abdomen with segments 1-7 unmodified and the 8th segment reduced, a gibbous face, a relatively unmodified third antennal segment and a cylindrical 2-segmented palpus (Hull, 1962; Baker and Fischer, 1975).Laphria species are often called bee-like robber flies as many are mimics of bees, especially Bombus spp., and a few resemble wasps. Adults are generalist ambush predators that prey on a wide array of insects and arthropods (Lavigne et al. 1978). There are 63 described species of Laphria in North America, 24 of which occur in eastern Canada and the bordering northern United States (Fisher and Wilcox, 1997). The remaining two eastern Canadian Laphria species are undescribed.

Most of the relatively few works dealing with the Nearctic species have been taxonomic surveys. McAtee (1918) provides a key to the Nearctic species, Bromley (1934) provides a key to the North American species, Baker and Fischer (1975) provide a key to the Laphria of Michigan, and Bullington (2016) provides a key to one subgroup (Laphria s. str.) in eastern North America. These sparsely illustrated keys are either outdated or relatively difficult for non-specialists to use; they are also missing several species of eastern Canadian robber flies here treated as part of the genus Laphria. We here provide the first complete key to the Laphria of eastern Canada.

Systematics

Laphria was previously (and is occasionally still) diagnosed primarily on hair coloration and patterns, which we now know can vary greatly within species; this has resulted in confusion around species limits within the group. It has also led to Laphria species being historically misplaced, as many were reassigned to the genus Bombomima Enderleinonly to be later placed back into Laphria (Bullington, 1986). Similarly, some species of Dasyllis were at one time treated as Laphria due to their bee-like appearance (Bullington, 1986).Bullington (2016) includes three described North American genera in the tribe Laphriini: Laphria Meigen (Laphria sensu stricto), Choerades Walker, and Lampria Macquart. Lampria is a mostly Neotropical group represented in eastern Canada only by Lampria bicolor, which is included in our key because of its similarity to Laphria. Choerades is a mostly Old World group that has been treated either as part of Laphria (Baker and Fischer, 1975) or as a separate genus including several species originally described as Laphria (Hull, 1962; Nagatomi, 1964; Bullington, 1986; Lehr, 1992). Laphria including Choerades is an easily recognizable group in North America, but Laphria without Choerades is difficult to diagnose or define.In an unpublished thesis, Bullington (1986) groups the North American species here treated as Laphria (Laphria sensu lato) into four genera, placing some species (L. gilva, L. sicula and L. sadales) in the genus Choerades and reassigning several further species to two new genera. Recognition of these genera is based primarily or entirely on features of the male genitalia. Until such time as this classification is published and supported by strong data showing that the newly recognized genera are monophyletic we prefer to retain the conservative and pragmatic approach of using one name, Laphria, for all eastern Canadian members of the easily recognized and charismatic group of flies traditionally treated under that name.

Biology

Adult Laphria are opportunistic predators that are often found perching in sunlit areas waiting to catch prey on the wing. Like other Asilidae, they paralyze and digest prey using neurotoxins and proteolytic enzymes injected through the blade-like hypopharynx, a structure sheathed by the proboscis (Wood, 1981). The laterally compressed proboscis apparently facilitates the piercing of flying beetles between the elytra before they can be closed. Laphria are most often seen perched on the trunks and branches of trees, fallen logs or foliage; they also sometimes perch on rock surfaces (Bullington, 1986). They often perch adjacent to streams, paths and forest edges. Most species have preferences for perch type and height (Wood, 1981). The larvae of Laphria are predaceous, developing in plant roots or decaying wood where they prey on wood-boring or soil-dwelling insects (Lavigne et al. 1978).

Specimen data were obtained for the University of Guelph Insect Collection (DEBU), the Royal Ontario Museum (ROM) and the Canadian National Collection of Insects, Arachnids and Nematodes (CNC).

Terminology used in the key follows the Manual of Nearctic Diptera (McAlpine et al., 1981) and is depicted in Figures 1–5. The use of the word “tergite” refers to abdominal tergites. Diagnoses for species are based on specimens from the University of Guelph Insect Collection where possible, but in some cases photos of type specimens were used instead. When only one specimen of a species was available, photos from BugGuide (https://bugguide.net/node/view/ 15740) were used to indicate variation within species. Diagnoses were checked against the original descriptions, Bullington (1986), and Baker and Fischer (1975). Body length data were supplemented from the literature. Flight ranges were determined using label data from DEBU and CNC. Distribution maps were created using the online software SimpleMappr (Shorthouse 2010). Locations were obtained from specimen data labels and were converted to GPS coordinates using Google Maps GPS Coordinates (https://www.gps-coordinates.net). Non-Ontario distributions were mapped using whole provinces, territories or states to indicate the presence of Laphria within these jurisdictions. Specimen photographs were taken using a Canon DSLR mounted on a Stackshot rail, and then stacked using Helicon Focus. All photographs of living flies were taken by the second author unless otherwise indicated.

Table 1. Checklist of eastern Canadian Laphria. ON, Ontario; QC, Quebec; NB, New Brunswick; NS, Nova Scotia; PEI, Prince Edward Island; LB, Labrador; NF, Newfoundland. *Record is not verified.