The Bee Flies (Diptera: Bombyliidae) of Ontario, with a Key to the Species of Eastern Canada
CJAI 06 March 06, 2008
doi: 10.3752/cjai.2008.06

Joel H. Kits* , Stephen A. Marshall* , and Neal L. Evenhuis**

* Department of Environmental Biology, University of Guelph, 50 Stone
Rd. E., Guelph, Ontario N1G 2W1, Canada jkits@uoguelph.ca, samarsha@uoguelph.ca

** Department of Natural Sciences, Bishop Museum, 1525 Bernice Street,
Honolulu, Hawaii 96817, USA neale@bishopmuseum.org

Introduction
Significant species
Biology
Taxonomic problems
How to use the key
Acknowledgements
References

Introduction

It is astonishing that a diverse group of animals as attractive as the bee flies — fuzzy, colorful and conspicuous — should have been entirely neglected by a whole generation of Canadian entomologists, naturalists and ecologists. It is also unfortunate, for we have been almost completely ignorant of the many remarkable bombyliid species associated with habitats ranging from agro-ecosystems through to threatened dunes, grasslands and peatlands. The only possible reason for the dearth of bombyliid studies in Canada is the taxonomic impediment. Bee flies, like many arthropods, have been flying below the zoological radar screen because of the impression that they are difficult to identify. One of the main objectives of this paper is to correct that impression, or at least put it in the past tense.
The taxonomy of North American bee flies is relatively mature, with a complete recent catalog (Evenhuis and Greathead 1999) and a rich taxonomic literature. However, published keys are generally difficult to use and poorly illustrated, some being over 100 years old; it would be extremely difficult, if not impossible, to use the existing taxonomic literature to identify most Ontario bee flies without access to a good reference collection. We have combined our own recent observations with the extensive data available from regional insect collections (especially the University of Guelph Collection) to review the fauna and develop a list of bee flies occurring in or near Ontario. We have also used this material to generate photographs showing general appearance and all key characters of 73 species now known from Ontario or nearby areas. These photographs allowed the development of the first user-friendly key to eastern Canadian bee flies, and the collection-based review led to the discovery of an unexpectedly rich fauna. Prior to this review the majority of Ontario’s bee fly species were not even recognized as occurring in the province. Evenhuis and Greathead (1999) recorded 13 genera and 29 species from Ontario; we now have records of 24 genera and 61 species from Ontario. Included in these unrecognized records are 5 genera and 25 species we first record here for Ontario, of which 3 genera and 20 species are also new for Canada (see checklist below).

Significant species

We have given brief notes on the Ontario distribution in each species treatment; however, some species are especially significant because of their apparent rarity or habitat-restriction. Two species (Toxophora amphitea Walker and Poecilanthrax bicellata (Macquart)) are known only from one or two southern Ontario grasslands (Ojibway Prairie and Walpole Island), and another (Paravilla separata (Walker)) is known only from Walpole Island, Pinery Provincial Park and St. Joseph Island. Others (Dipalta banksi Johnson, Chrysanthrax dispar (Coquillett), Bombylius fraudulentus Johnson, and the Ontario species of Geron (Geron) Meigen and Tmemophlebia Evenhuis) are dune grassland associates; except for D. banksi, these are all known from very few sites. Villa fumicosta Painter is known from only two Ontario sites, both peatlands. Other very rarely collected species in Ontario without the apparent habitat restrictions of the dune, grassland and peatland species include Apolysis sigma (Coquillett), Anastoechus barbatus Osten Sacken, Bombylius atriceps Loew, Aldrichia ehrmanii Coquillett, Metacosmus mancipennis Coquillett, Anthrax argryopygus Wiedemann, Anthrax pauper (Loew), and Anthrax pluto Wiedemann.Some of these species may be more common than collecting records suggest. For example, Anthrax argyropygus and Anthrax pauper are both known in Ontario only from historical (1919) specimens labeled “Jordan, Ontario”. We have relatively few recent specimens from the Niagara region of Ontario so it is possible that this apparent rarity/disappearance is a collecting artifact. Anastoechus barbatus is known to occur both in western Canada and the James Bay region of Quebec, and probably occurs across boreal Ontario; the lack of records may be due in part to the limited collecting effort in that range. Both Apolysis sigma and Metacosmus mancipennis are small and easily mistaken for other families (Empididae and Pipunculidae, respectively), which may cause general collectors to bypass them. For the most part, the habitat and host requirements of these rarely collected species are unknown, and may in some cases be limiting factors in their abundance.

Biology

Most bee flies are ectoparasitoids, with active first instar triungulin larvae that attach themselves to hosts, usually insect larvae, in concealed places such as burrows or nests. Although hosts remain unknown for the majority of Canadian species, most of the species with known hosts are ectoparasitoids of solitary bees and wasps and are thus most likely to be encountered in the kinds of open, dry habitats that support the greatest diversity of aculeate Hymenoptera. Some of the bee flies found seeking hosts over open, sandy ground attack hosts other than bee and wasp larvae, including grasshopper egg pods (Anastoechus Osten Sacken, Systoechus Loew), tiger beetle larvae (some Anthrax Scopoli), or antlions (Dipalta Osten Sacken). Several groups, including Villa Lioy, Exoprosopa Macquart, Systropus Wiedemann and the Phthiriini, are parasitoids (usually endoparasitoids) of moth larvae and pupae. Some, such as Hemipenthes Loew, have been recorded as hyperparasitoids of other parasitoids that attack caterpillar and sawfly hosts (Hemipenthes species also attack the caterpillar and sawfly hosts). Host use in the Bombyliidae has been comprehensively reviewed, most recently by Yeates and Greathead (1997). Little work has been done specifically on host use in eastern Canada, although Packer (1988) found Bombylius pulchellus Loew to be a major cause of brood mortality in the halictid bee Halictus ligatus Say in Ontario.
Host and habitat data, where known, are given under each genus or species below, generally derived from Hull (1973) and Yeates and Greathead (1997).

Taxonomic problems

Although bee flies are relatively well known taxonomically, there are some remaining taxonomic issues that need to be resolved. Problems in some genera include difficulties both in assigning the correct names to Ontario taxa and in evaluating the distinctiveness of closely related forms. Of the taxa occurring in Ontario, the most problematic is the genus Villa. This is the largest genus in Ontario, but the most comprehensive key dates to the 19th century (Coquillett 1892b). Little has been published on Villa since then, and a thorough revision is required. Recent revisions of the Nearctic fauna are also lacking for several related genera, including Hemipenthes, Chrysanthrax Osten Sacken, and Exoprosopa, although Ontario has only a few species in each of these genera. The subgenus Geron (Geron) was recently revised (Hall and Evenhuis 2003), but species of this subgenus remain difficult to identify since the key relies on dissection and it is necessary to compare genitalia to published figures or reference specimens.
Some apparent pairs of very similar species currently treated as distinct require further study, as some might turn out to be single, variable species. Painter and Painter (1962) suggested that this might be the case for Lepidophora lutea Painter and the southeastern L. lepidocera (Wiedemann), and Hall and Evenhuis (1981) suggested the same for Systoechus vulgaris Loew and S. candidulus Loew. Dipalta banksi and the widespread D. serpentina (Osten Sacken), like some pairs of very similar Villa species, also need to be critically compared in the context of thorough taxonomic revisions.

How to use the key

The majority of species will be identifiable by reference to the species plates, but if in doubt it is best to begin with the dichotomous keys. There is considerable variation in some bee fly species: sexual dimorphism is frequent, and body size and colour often vary between specimens of the same species. Individuals occasionally show aberrant wing venation, sometimes with extra or missing crossveins. Hairs are easily rubbed off specimens; although many rubbed specimens can be identified by comparison with intact individuals, some can become impossible to identify when heavily denuded (particularly Villa species).
Non-technical terms have been used whenever possible in the keys, and where technical terms are used for brevity or clarity they are explained where they first appear in the key. An exception to this is the use of terms referring to the setae or hairs that typically cover bee flies’ bodies. These setae are separated into pile, referring to long, thin, and usually erect setae, and tomentum, referring to thicker, curly or flattened setae pressed against the body surface. Other terms are occasionally used when particular groups of setae do not fit these broad categories, and the term scales has been used to refer to either flattened hairs on appendages or to the long, erect, flattened hairs on the abdomen of some Lepidophora and Villa species. Measurements given in the key and species notes refer to body length excluding the antennae and proboscis, and are derived from Ontario specimens when possible. There is considerable variation in body size in most Bombyliidae, and some specimens may fall outside of the ranges recorded here.
This key is focused on the fauna of Ontario, and we have restricted distribution notes to this province due to the paucity of records from the other eastern provinces. However, the key covers all species we know or expect to occur in eastern Canada, including apparently coastal species (such as Bombylius incanus Johnson and Villa shawii (Johnson)) which probably do not occur in Ontario. The key also covers the majority of species occurring in the northeastern United States. Bee fly diversity increases dramatically to the south and west, and less than 8% of the Nearctic species listed by Evenhuis and Greathead (1999) are included in this key.

Acknowledgements

We thank J. M. Cumming and J. Skevington (CNCI, Ottawa), B. Hubley (ROME, Toronto), R. Roughley (JBWM, Winnipeg), and Nigel Wyatt (BMNH, London) for giving us access to specimens under their care. C. Lambkin and an anonymous reviewer provided many helpful comments that greatly improved the quality of this key. We also acknowledge Dave Cheung for help with graphics and all personnel in the University of Guelph Insect Systematics laboratory for providing much of the material used in this study. Danielle Fife and Nick Moore assisted with testing the keys.
This work was funded in part by an NSERC discovery grant to the second author.

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