Robert A. Cannings. 1998. Robber Flies (Insecta: Diptera: Asilidae) in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

ROBBER FLIES
(INSECTA: DIPTERA: ASILIDAE)

Robert A. Cannings

RECOMMENDATIONS FOR FUTURE INVENTORY, RESEARCH AND MONITORING

There has never been any significant systematic inventory of asilid flies in the Montane Cordillera. Knowledge of the distribution and status of the species on the list in Appendix 1 has come from sporadic collecting over many years and analysis of specimens in the Royal B.C. Museum, Victoria; Spencer Entomological Museum, University of B.C., Vancouver; and the Canadian National Collection, Agriculture and Agrifood Canada, Ottawa. The only detailed study of the fauna of one locality was by Cannings (1989), who published an annotated list and biogeographic outline of the species collected in a Festuca grassland at Penticton over several years. Even in the southern valleys, much more work is necessary.

Outside the Okanagan drainage no formal inventories have been made anywhere in the zone. High priorities for future inventories are the species-rich, lowland valleys of the Kootenay and Thompson regions and the grasslands and dry forests of the Chilcotin Plateau. For clarifying the ranges of northern species, intensive work in the Cariboo, Omineca and Rocky Mountains; the Bulkley Valley, and the Babine Upland is required.

Increased inventory efforts would especially improve our knowledge of the species that might range widely across the zone but are known from few localities: for example, Leptogaster arida, Laphria index, L. milvina, L. scorpio, Callinicus pollinosus, Cyrtopogon lineotarsus, Eucyrtopogon punctipennis, E. comantis, Willistonina bilineata, Dioctria pusio, Machimus callidus, M. erythocnemius and Neoitamus brevicomus. Cyrtopogon falto Walker, one of the most common robber flies in eastern North America, ranges west sparsely in the transition forests of the Great Plains and appears again in the Skeena Valley of west- central British Columbia. It probably occurs across the northern part of the Montane Cordillera, but has never been recorded in the zone; further inventory in the north would answer this and other distributional questions.

Other species are apparently truly rare and their status needs to be elucidated. Among these are the grassland/dry forest species Leptogaster fornicata, Nicocles utahensis, Dicolonus nigricentrum, Dioctria henshawi, Ospriocerus aeacus, and Willistonina bilineata. Megaphorus willistoni and Stichopogon fragilis, each known only from one specimen in the arid grasslands of the South Okanagan/Similkameen, require study to assess their potentially threatened status.

Taxonomic work is required to clarify the identity and presence of species in a number of genera in the region. Leptogaster, Lestomyia, Nicocles, Eucyrtopogon, and Machimus especially are in need of revision. There are undescribed species in all these genera. A detailed examination of some of the larger genera in the Ecozone, such as Cyrtopogon and Laphria, will likely also result in new species.

No studies examining the effects of human activity on robber flies (e.g. the effects of overgrazing; the removal of coarse woody debris in logging operations) have been done in the ecozone, and no long-term monitoring studies are in place that could detect changes in species composition and abundance of asilid populations. Our knowledge of the habitat requirements of most species is nonexistent and more autecological studies would be helpful.