Cyrtopogon willistoni

Curran, 1922

Cyrtopogon willistoni is a of robber fly in the Asilidae, first described by Curran in 1922. The species has been studied in southwestern Montana, where it functions as an opportunistic of small insects. Males exhibit elaborate courtship involving audible airborne visual displays and possess distinctive silvery-white combs of hairs on their foretarsi. The species shows strong thermoregulatory dependence on direct sunlight for sustained .

Pronunciation

How to pronounce Cyrtopogon willistoni: /sɜːrtəˈpoʊɡɒn ˌwɪlɪˈstoʊnaɪ/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Males can be distinguished by the presence of silvery-white combs of hairs on the foretarsi, structures used during . As with other Cyrtopogon , identification to species level requires examination of male genitalia and specific chaetotaxy patterns. The species lacks the distinctive color patterns seen in some , presenting a generally dull coloration typical of the .

Habitat

Documented from southwestern Montana in open where perching substrates are available. Observations from Colorado suggest occurrence in foothill and montane environments including scrub oak and mixed conifer forest edges. The requires sunny conditions for activity, suggesting preference for open or edge habitats rather than dense forest interior.

Distribution

Recorded from southwestern Montana and Colorado (El Paso County). The appears to have a western North American distribution, though precise range boundaries remain incompletely documented. GBIF and iNaturalist records suggest broader western US occurrence, but specific locality data require verification.

Seasonality

active during summer months. Documented observations from June in Colorado and inferred summer activity period in Montana based on study timing. Peak activity likely coincides with warm, sunny conditions necessary for and .

Diet

Opportunistic of relatively small insects from at least 25 across 7 orders. Diptera comprise 44% of prey, 21%. Specific documented prey include Cicadellidae (leafhoppers), Bibionidae (March flies), and Formicidae (ants), which together constitute 44% of identified prey items.

Behavior

Males perform elaborate courtship involving audible airborne visual displays. Perching individuals exhibit lateral and basking postures for . Strong capacity is apparently limited to periods of direct sunlight availability, indicating behavioral thermoregulation. Foraging behavior involves opportunistic from perches.

Ecological Role

in terrestrial , contributing to of small flying insects including Diptera, , and Formicidae. The ' thermoregulatory constraints may influence its functional role in community dynamics relative to more thermally tolerant predators.

Similar Taxa

Cyrtopogon ruficaudaSimilar size and general ; distinguished by differences in male terminalia and absence of distinctive foretarsal hair combs in C. willistoni males
Other Cyrtopogon species members share general body plan and predatory habits; specific identification requires examination of male genitalia and tarsal structures, with C. willistoni males uniquely possessing silvery-white foretarsal combs

More Details

Thermoregulatory constraints

Unlike some larger robber flies capable of endothermic warming, C. willistoni appears dependent on behavioral and direct solar radiation for muscle function. This may limit foraging and mating activity to specific weather conditions and times of day.

Courtship morphology

The silvery-white combs of hairs on male foretarsi represent sexually dimorphic structures used in visual displays during courtship. Such elaborate male ornamentation is relatively uncommon in the Asilidae and suggests strong .