Megaphorus guildianus (Williston),

Lavigne, Robert J. & Dennis, Steve, 2019, Robber flies (Insecta: Diptera: Asilidae) of Wyoming, USA with keys to genera and species, Zootaxa 4662 (1), pp. 1-126: 50

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Megaphorus guildianus (Williston)


Megaphorus guildianus (Williston) 

Mallophora guildiana Williston, 1885: 60  .

Recognition characters: Yellow species; length 9–13 mm; mystax straw white; thorax yellow pilose, scutellar setae yellowish white; scutellar bristles lacking; wings brownish; abdomen yellow pilose, lateral setae on first abdominal segment yellowish white; legs, femora and tibiae orange with thick yellow setae, apex of hind tibiae with majority of bristles black, reddish brown with setae yellow above tarsi.

Distribution: FREMONT: Lander, WANG, LTA, 8 Aug. 2004 ( CSU, GMAD). HOT SPRINGS: Dutch Nick Flats, Big Horn Basin, 25 July 1962 ( CK). GOSHEN: Lingle, 4 Aug. 1965 ( MHB) (specimen in NMSCA). LARA- MIE: Pine Bluffs, 29 July–2 Aug. 1967 ( WAN). NIOBRARA: Lance Creek, 5 Aug. 1995 (Wheeler-AMNH); Niobrara Co., 17 Aug. ( REP, JW), 17 Aug. 1945 ( REP) (specimen in CAS). PLATTE: Glendo, 19 Aug. 1959 (specimen in CAS), 6 July 1964 ( FRH) (specimen in NMSCA); Glendo, 5 Aug. 1959 (specimen in CAS), 5 Aug.–3 Sept. ( REP, JW). Dwyer numerous records, 6 July–3 Sept. ( RJL); Camp Guernsey, WANG, 2001b ( CSU, GMAD); Guernsey, 18 Aug. 1974 ( RJL) (specimen in MNSU, NMSCA); Guernsey, numerous records 14 July–6 Sept. ( LJS, RJL, SD); Twin Pine Ranch, 13 km W of Dwyer, 25 Aug. 1966 ( RJL, MHB); Wheatland, 5–25 Aug. 1964 ( RJL, FRH), 27 Aug. 1965 ( FRH); 37 km N of Wheatland, numerous records, 6 July–29 Aug. ( SD). SHERIDAN: Sheridan, WANG, LTA, 17 July 2006 ( CSU, GMAD); 8 km N Sheridan, 6 Aug. 1963 ( GEB, PT) (specimen in CAS). TETON: Jackson, 21 June 1961 ( VR). Recorded from Wyoming by: Cole & Pritchard, (1964) (Glendo, Lance Creek, Niobrara Co.); Dennis & Lavigne (1975) [as Mallophorina guildiana  ; as prey of Proctacanthus milbertii  (as Proctacanthus micans  )], (1976b) (pupal case; as Mallophorina guildiana  ), (1976c) (as prey of Efferia varipes  ), (2007) (as Megaphorus guildiana  ); Dennis et al. (2008) (pupal case; as Megaphorus guildiana  ); Geller-Grimm (2018); Lavigne & Holland (1969) [as Mallophorina guildiana  ; as prey of Diogmites angustipennis  , Pogonioefferia pallidula  (as Efferia pallidula  )]; Lavigne et al. (1976) [as Mallophorina guildiana  ; as prey of Pogonioefferia benedicti  (as Efferia benedicti  )], (1994).

Habitat: Sagebrush steppe and wheatgrass-needlegrass shrub steppe shrub and grassland, and grama-needlegrass-wheatgrass and grama-buffalo grass grassland vegetation types. Open range, short- to mid-grass plains in areas having a high forb density (see Dennis & Lavigne 1975, as Mallophorina guildiana  ).

Ethology: Usually forages from vegetation, and only rarely lands on the ground or a rock (e.g., when the sun is obscured by clouds) (see Dennis & Lavigne 1975).

Prey: COLEOPTERA  , DIPTERA  , HEMIPTERA  (as Heteroptera and Homoptera), HYMENOPTERA  (see Dennis & Lavigne 1975; Rogers & Lavigne 1972, both as Mallophorina guildiana  ).


Colorado State University


Forest Research Station


Desert Experiment Station of the W.I.R.


California Academy of Sciences


Scientific Research Centre


San Diego Natural History Museum














Megaphorus guildianus (Williston)

Lavigne, Robert J. & Dennis, Steve 2019

Mallophora guildiana

Williston 1885: 60