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robber flies

Family Asilidae

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Overview • Description • Distribution • Taxonomy

Overview

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 moustache (mystax) and a beard. 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
			Sources 7, 24, 27, 29, 30, 82.
	6/25/2022


	Taxonomy
	Order	Diptera (flies)
	Suborder	Brachycera
	Infraorder	Asilomorpha (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

	Orthorrhapha was historically one of two infraorders of Brachycera, a suborder of Diptera. However, Brachycera did not contain all of the descendants of the last common ancestor (paraphyletic). It was split into five extant (still existing) and one extinct infraorder. Orthorrhapha is now considered obsolete and has not been used in decades, but it persists in printed literature and on some online sources. A recent revision of the order Diptera (Pope, et al., 2011) revived the name Orthorrhapha, but this has not been widely accepted.

	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

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	Katie P

	Resting on my patio; was able to approach for photos without startling it. Teaspoon in pic for scale.



	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.


	Pheasantpete

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


	Jeff Schneider

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


	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

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


	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.





	MinnesotaSeasons.com Photos

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	Slideshows


	Robber Flies Andree Reno Sanborn

	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


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Visitor Sightings

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Katie P 6/23/2022	Location: Ely, MN Resting on my patio; was able to approach for photos without startling it. Teaspoon in pic for scale.



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.



Pheasantpete 7/31/2021	Location: Winona County Stream I believe this is a robber fly but I am open to comments if misidentified.



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.



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



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.



Bill Reynolds 8/22/2003	Location: St. Louis Co. It looks like it has caught a Crane fly for dinner.



MinnesotaSeasons.com Sightings