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Robberfly (Efferia spp.)


Detailing the physical features, habits, territorial reach and other identifying qualities of the Robberfly.

 Updated: 8/14/2018; Authored By Staff Writer; Content ¬©www.InsectIdentification.org




One could mistake a Robberfly from the genus Efferia for some kind of strange black-and-white bee.



Robberflies are considered 'hanging thieves' becaue they use their arms to suspend themselves from twigs and branches and steal a meal from unsuspecting flying insects. A passerby like a bee, wasp or other fly don't see them as they roam. If they are spotted and within range, the Robberfly will chase the flying insect, eventually overtaking them. Once caught, the Robberfly uses its legs to hold the prey and carry it to a nearby plant. It then uses its sharp mouth to stab the victim and then suck out the victim's insides.

They make a loud whirring noise as they fly because they beat their wings so rapidly. The Efferia species male is slightly darker than the female. At the tip of the male's abdomen is black 'bulb' Females do not have this feature; instead they have long needle-like ovipositors, which they use to inject their fertilizes eggs into the soil. It may look like a stinger at first glance, but it is not a stinger. Both genders can be found hanging around in open fields, parks, meadows and other dry areas.




Taxonomic Hierarchy
Kingdom: Animalia
  Phylum: Arthropoda
    Class: Insecta
      Order: Diptera
        Family: Asilidae
          Genus: Efferia
            Species: spp.
Identifying Information
Scientific Name: Efferia spp.
Other Name(s): Robber fly
Category: Fly or Mosquito
Size (Adult; Length): 13mm to 19mm (0.51in to 0.74in)
Colorwheel Graphic Colors: white; black; gray; brown
Descriptors: flying, buzzing, noisy, fast, shiny, metallic
Territorial Map
Alaska  
Hawaii  
Prince Edward Is.  
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Territorial Reach (A-to-Z)
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
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Alberta
British Columbia
Manitoba
New Brunswick
Newfoundland and Labrador
Nova Scotia
Ontario
Prince Edward Island
Quebec
Saskatchewan
Mexican National Flag Graphic
Mexico
Note: An insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above as they are driven by environmental factors (such as climate change), available food supplies and mating patterns. Grayed-out selections indicate that the subject in question has not been reported in that particular territory. U.S. states and Canadian provinces / territories are clickable to their respective bug listings.