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Robber  Fly   -

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Family Asilidae - Robber Flies

Reference source :

Adisoemarto, S. 1967. The Asilidae (Diptera) of Alberta. Quaest. entomol. 3: 3-90.

Adisoemarto, S. and D.M. Wood. 1975. The nearctic species of Dioctria and six related genera (Diptera, Asilidae). Quaest. entomol. 11: 505-576.

Artigas, J.N. and N. Papavero. 1988. The American genera of Asilidae (Diptera): keys for identification with an atlas of female spermathecae and other morphological details. Part I. Key to subfamilies, subfamily Leptogastrinae. Gayana Zool. 52: 95- 114.

Cannings, R.A. 1989. The robber flies (Diptera: Asilidae) of a Festuca grassland in the Okanagan Valley, British Columbia. J. entomol. Soc. Brit. Columbia 86: 14-26.

Cannings, R.A. 1993. New synonomy of Rhadiurgus variabilis (Zetterstedt) (Diptera: Asilidae) with notes on morphology, natural history, and geographical variation. Can. Ent. 125: 337- 354.

Cannings, R.A. 1994. Robber Flies (Diptera: Asilidae) new to Canada, British Columbia, Yukon, and the Northwest Territories with notes on distribution and habitat. J. entomol. Soc. Brit. Columbia 91: 19-26.

Cannings, R.A. 1997. Robber Flies (Diptera: Asilidae) of the Yukon. pp. 637-662 in H.V. Danks and J.A. Downes (Eds.). Insects of the Yukon. Biological Survey of Canada (Terrestrial Arthropods), Ottawa. 1034 pp.

Cannings, R.J. and S.G. Cannings. 1996. British Columbia: a natural history. Douglas and McIntyre. Vancouver.

Cole, F.R. and J. Wilcox. 1938. The genera Lasiopogon Loew and Alexiopogon Curran in North America (Diptera - Asilidae). Ent. Amer. 18: 1-91.

Curran, C.H. 1923. Studies in Canadian Diptera. I. Revision of the asilid genus Cyrtopogon and allied genera. Can. Ent. 55: 92- 95, 116-125, 132-142, 169-174, 185-190.

Fisher, E.M. 1986. A reclassification of the robber fly tribe Andrenosomini, with a revision of the genus Dasyllis Loew (Diptera: Asilidae). Unpublished doctoral thesis. University of California, Riverside. 238 pp+illustrations.

Fisher, E.M. and J. Wilcox. 1997. Catalogue of the robber flies (Diptera: Asilidae) of the Nearctic Region. Unpublished preliminary draft.

Foxlee, H.R. 1942. A list of nineteen species od Asilidae collected at Robson, B.C. (Diptera). Proc. entomol. Soc. British Columbia (1941) 38: 14.

Hebda, R.J. 1982. Postglacial history of grasslands of southern British Columbia and adjacent regions, Pp. 157-191 in A.C. Nicholson, A. McLean and T.E. Baker (Eds.). Grassland ecology and classification symposium proceedings. British Columbia Ministry of Forests, Victoria.

Hebda, R.J. 1995. British Columbia vegetation and climate history with focus on 6ka BP. Géographie Physique et Quaternaire 49: 55- 79.

Hull, F.M. 1962. Robber flies of the world: the genera of the family Asilidae. Bull. U.S. Nat. Mus. 224: 1-907.

Knutson, L.V. 1972. Pupa of Neomochtherus angustipennis (Hine), with notes on feeding habits of robber flies and a review of publications on morphology of immature stages (Diptera: Asilidae). Proc. Biol. Soc. Wash. 85: 163-178.

McAlpine, J.F. 1979. Diptera. Pp. 389-424 in H.V. Danks (Ed.), Canada and its insect fauna. Mem. Ent. Soc. Can. 108: 1-573.

Martin, C.H. and J. Wilcox. 1965. Family Asilidae. Pp. 360-401 in Stone, et al. (Eds.), A catalogue of the Diptera of America north of Mexico. U.S. Department of Agriculture, Agriculture Research Service, Agriculture Handbook 276.

Melin, D. 1923. Contributions to the knowledge of the biology, metamorphosis and distribution of the Swedish asilids in relation to the whole family of asilids. Zool. Bidr. Upps. 8: 1-317.

Theodor, O. 1980. Diptera: Asilidae. Fauna Palestina: Insecta II. The Israel Academy of Sciences and Humanities, Jerusalem. 446 pp.

Wilcox, J. 1966. Efferia Coquillett in America north of Mexico (Diptera: Asilidae). Proc. Calif. Acad. Sci. 34: 85-234.

Wilcox, J. and C.H. Martin. 1936. A review of the genus Cyrtopogon Loew in North America (Diptera - Asilidae). Ent. Amer. 16: 1-95.

Wood, G.C. 1981. Asilidae [chapter 42]. Pp. 549-573 in McAlpine et al. (Eds.), Manual of Nearctic Diptera. Vol. 1. Agriculture Canada Monograph 27: vi + 1-674.


Feeding : Robber flies catch and eat insects. They eat anything small enough for them to handle, including flies, wasps, spiders, and moths.

More detail in photos...

Mating  : The above picture show a Robber fly mating pair. The male and female are look similar and it is difficult to differentiate which is which.  More photo details...

Robber flies have powerful piercing-sucking mouthparts. The tops of their heads behind the eyes are hollowed out. Robber flies usually have long, tapering abdomens.

They  are about 1cm long.


The Robber Flies are air hunter. They also known as an Assassin Fly and  can be found in forest, bush land and garden. They have strong legs which can catch prey on flight. They are medium to large size flies with large eyes and necked head.

They are active predators on flying insects, unselective in prey species. They even prey on web weaving spiders. Their mouthparts are the triangular proboscis  which insert into prey and suck the juice. Robber flies are active predators. They usually rest on leaf or stick about one to two meters above ground, watching if there is any prey flies pass. Robber flies will capture prey by their powerful legs in mid air and consume while on the wings.

Their mouthpart is the large pointed proboscis. Their thorax and legs are hairy. Their abdomen are long and thin. They are commonly seen in backyard garden and in the bushes.

Most Robust flies are with noticeable "beard" of setae around the face. It is believed that they serve as protection to their face from damage by their prey.

Location : Kampong Merotai, Tawau, Sabah, Malaysia

Date : Photographs on 3 different days in September 2006

Size : 1.5 cm

This Robber Fly wasn't all that concerned about me taking its photographs. It often rests on leaves and branches with a clear view of surrounding. It seizes its victim from above, pierces its body and sucks out juices, then drops the emptied prey.

From the back view this Fly is dull and nothing special. Only after viewing this Robber Fly carefully in detail then I realize this tinny fly is such a muscular handsome bug.


When I noticed from the photos the Yellow Bulbs beside the abdomen of this Robber Fly my first thought was they are yellow flower pollens attached to this bug after it visited some flowers. After checking in the internet, I came to know that some other Robber Flies also have similar BULB on the abdomen. So this yellow BULB is not pollen not fungus. But what they are ? What function to the fly ?

(I found the answer on 3 Oct 2006 from :






INDEX : Insects   January 12, 2016 03:12:55 AM