robber fly

Family Asilidae

Overview
robber fly (Family Asilidae)
Photo by Kirk Nelson
 

Asilidae is a large family of predatory flies known as robber flies. There are more than 7,500 described species worldwide, about 1,400 species in North America north of Mexico, and at least 47 species in Minnesota. They are found in a variety of habitats but mostly in open, sunny, dry locations. Larvae live in the soil, rotting wood, or decaying organic material on the ground. Some prey on the larvae of other insects. Adults prey mostly on winged insects, often larger than themselves, but also on other insects and spiders. If handled they can deliver a painful bite.

     
           
 
Description
 
 

Robber flies are powerfully built. The legs and thorax are relatively large. Most have a long, tapering abdomen. Some are robust, resembling a bumble bee. Some have a very long and slender abdomen, resembling a damselfly. They range from bare to very hairy, but most have a beard (mystax). There are two large compound eyes on the side of the head and three small simple eyes (ocelli) in a triangle on top of the head. The top of the head is depressed (“hollowed out”) between the compound eyes. The ocelli are on a prominent rounded projection (tubercle) between the compound eyes. The mouthparts are modified for piercing and injecting saliva which paralyzes the prey. The antennae have 3 segments. The third segment is elongated and sometimes has a short bristle-like process (style) at the end.

 
     
 
Distribution
 
 

Distribution Map

 

Sources

7, 24, 27, 29, 30, 82.

 
  8/27/2021      
         
 
Taxonomy
 
 

Order

Diptera (gnats, mosquitoes, true flies)  
 

Suborder

Brachycera (circular-seamed flies, muscoid flies, short-horned flies)  
 

Infraorder

Orthorrhapha  
 

Superfamily

Asiloidea  
       
 

Subordinate Taxa

 
 

Subfamily Asilinae

Subfamily Bathypogoninae

Subfamily Brachyrhopalinae

Subfamily Dasypogoninae

Subfamily Dioctriinae

Subfamily Laphriinae

Subfamily Laphystiinae (?)

Subfamily Leptogastrinae

Subfamily Ommatiinae

Subfamily Phellinae

Subfamily Stenopogoninae

Subfamily Stichopogoninae

Subfamily Tillobromatinae

Subfamily Trigonomiminae

Subfamily Willistonininae

 
       
 

Synonyms

 
 

 

 
       
 

Common Names

 
 

robber flies

 
       

 

 

 

 

 

 

Glossary

Mystax

On flies, especially in the family Asilidae, a patch of bristles or hairs (mustache) immediately above the mouth.

 

Ocellus

Simple eye; an eye with a single lens. Plural: ocelli.

 

 

 
 
Visitor Photos
 
           
 

Share your photo of this insect.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Attach one or more photos and, if you like, a caption.
 
 

Dan W. Andree

 
 

Robber Fly with lunch...

Seen it land so went to see what it was and this is it. I filmed it in 4k and it stayed perched with its prey for some time occasionally flying up in air a foot or so and landing on the same spot. Looks like it had one of those yellow jackets/wasps.

I had seen robber flies before but not one with anything it caught. A prairie preserve in Norman Co. Mn. is where I came across it.

  robber fly (Asilidae)  
 

Pheasantpete

 
  I believe this is a robber fly but I am open to comments if misidentified.   robber fly (Asilidae)  
 

Jeff Schneider

 
  it landed on the edge of our boat on Little Pine Lake, near Parham MN.   robber fly (Asilidae)  
 

Bill Reynolds

 
 

Hunting flies.

Image cropped to give some idea of size. The screw is a typical dry wall screw of an 1.5 inch

  robber fly (Asilidae)  
           
 

Machimus sp. female

It looks like it has caught a Crane fly for dinner.

  robber fly (Machimus sp.)  
 

Kirk Nelson

 
  I had taken a photo of an interesting insect, and when I looked more closely, I could see it had captured another insect.   robber fly (Asilidae)  
         
      robber fly (Asilidae)  
           
 
MinnesotaSeasons.com Photos
 
 

 

 
           
           

 

Camera

     
 
Slideshows
 
Robber Flies
Andree Reno Sanborn
  Robber Flies  
 
About

Family Asilidae

In North America, 883 species(1)

About 530 general and 7,000 described species worldwide (Asilidae Home Page)

Medium-sized to large predatory flies, often perch in exposed location and make short flies after prey. Typical family characteristics:

top of head hollowed out between eyes, with three ocelli in this depression (diagnostic character)

body from very hairy to nearly bare

typical body form elongated, with tapered abdomen, but other forms as well

some groups mimics of hymenoptera

face usually "bearded", with prominent mystax

mouthparts modified to inject saliva into prey--saliva contains potent neurotoxic and proteolytic enzymes

mouthparts similar in both sexes, unlike typical blood-sucking flies, such as Tabanidae

antennae with three segments, third segment elongate and often with terminal style

source: bugguide.net

bugguide.net/node/view/151

 
     

 

slideshow

       
 
Visitor Videos
 
       
 

Share your video of this insect.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Attach a video, a YouTube link, or a cloud storage link.
 
 

 

 
     
     
       
       
       
 
Other Videos
 
     
     
     
       

 

Camcorder

 
 
Visitor Sightings
 
           
 

Report a sighting of this insect.

 
  This button not working for you?
Simply email us at info@MinnesotaSeasons.com.
Be sure to include a location.
 
  Dan W. Andree
8/23/2021

Location: A prairie preserve in Norman Co., Mn.

Seen it land so went to see what it was and this is it. I filmed it in 4k and it stayed perched with its prey for some time occasionally flying up in air a foot or so and landing on the same spot. Looks like it had one of those yellow jackets/wasps.

I had seen robber flies before but not one with anything it caught. A prairie preserve in Norman Co. Mn. is where I came across it.

robber fly (Asilidae)  
  Pheasantpete
7/31/2021

Location: Winona County Stream

I believe this is a robber fly but I am open to comments if misidentified.

robber fly (Asilidae)  
  Bill
8/8/2020

Location: Carver County, Dahlgren Township

Landed on my windshield with a grasshopper in it clutches.  Sat for a few minutes then flew away on a beeline to the woods.

 
  Lindsay Freeland
7/27/2020

Location: New London, MN

the kids found it. Appeared to have an injured wing.

   
  Steph
9/3/2017

Location: Oylen, MN 

   
  Jeff Schneider
7/28/2017

Location: Otter Tail County

it landed on the edge of our boat on Little Pine Lake, near Parham MN.

robber fly (Asilidae)  
  Bill Reynolds
8/22/2003

Location: Numedal Township, Pennington Co., Minnesota

Hunting flies. Image cropped to give some idea of size. The screw is a typical dry wall screw of an 1.5 inch

robber fly (Asilidae)  
  Kirk Nelson
8/18/2013

Location: Upper Sioux Agency State Park

I had taken a photo of an interesting insect, and when I looked more closely, I could see it had captured another insect.

robber fly (Asilidae)  
  Bill Reynolds
8/22/2003

Location: St. Louis Co.

It looks like it has caught a Crane fly for dinner.

robber fly  
           
 
MinnesotaSeasons.com Sightings
 
 

 

 

 

 

Binoculars


Last Updated:

About Us | Privacy Policy | Contact Us | © 2021 MinnesotaSeasons.com. All rights reserved.