Robber Fly Life Cycle: A Fascinating Journey Explained

Robber flies, belonging to the family Asilidae, are often considered fascinating and formidable predators in the insect world. As medium-sized to large, bristly or hairy flies, there are over 1,000 species of robber flies found in North America, with nearly 100 species recorded in the Upper Midwest alone Wisconsin Horticulture. These distinctive creatures derive their common name from their aggressive hunting behavior, as they are known for ferociously pouncing from the air on their prey.

The life cycle of a robber fly entails three basic stages: egg, larva, and adult. The specifics of their life cycle may vary depending on the species and their habitat preferences. As a general guideline, those robber flies that hunt on the ground will lay their eggs on or in the soil, while those that hunt from plants deposit eggs into the plant tissues MDC Teacher Portal.

Robber Fly Identification and Characteristics

Physical Features

Robber flies are distinctive and unique insects. Their most prominent features are:

  • Large compound eyes
  • Three simple eyes (ocelli) on the top of their head
  • A dense hair covering their face, called a mystax
  • Long, strong legs for grasping prey

Robber flies belong to the order Diptera, which also includes house flies, mosquitoes, and other familiar insects. They are in the suborder Brachycera and are part of the superfamily Asiloidea.

Family Asilidae and Order Diptera

Robber flies are part of the family Asilidae and the order Diptera. Key characteristics include:

  • Two wings for flying (typical for Diptera)
  • A short, strong proboscis for piercing and sucking prey

These features set them apart from other insects and make them efficient predators.

Subfamilies and Species

Robber flies are a diverse group with over 1,000 species found in North America alone. There are several subfamilies, each with unique features. For example, subfamily Laphriinae is known for its striking color patterns and wasp-like appearance.

Torsten Dikow, a prominent researcher on robber flies, has contributed extensively to the understanding of their classification within the Asilidae family.

Life Cycle and Development

Eggs

Robber flies lay eggs in different environments such as the soil or in plants. Adults deposit their eggs in clusters with each egg being small and cream-colored.

Larvae

After hatching, robber fly larvae are legless, slender, and shiny white in appearance. These larvae are predatory, feeding on eggs, larvae, or other soft-bodied insects, and go through several developmental stages. They usually reside in soil or decaying organic materials, depending on the species.

Pupa

When it is time to pupate, robber flies do so in the soil, where they overwinter. Some species take up to three years to develop from egg to adult, undergoing a series of molts and changes in appearance throughout the process.

Adults

Adult robber flies are characterized by their:

  • Two wings
  • Prominent spikes on their legs
  • Stout hairs on the body
  • Sharp, tube-like proboscis
  • Large, widely-spaced compound eyes

These features make adult robber flies well-adapted predators, capable of capturing and feeding on various flying insects. Moreover, some robber flies are known to mimic the appearance of bees and wasps to deter potential predators.

Habitat and Distribution

Robber flies are found in various habitats across the globe, from North America to tropical regions, adapting to various environments like desert climates and woodland areas.

North America

In North America, over 1,000 species of robber flies can be found. These predators are often confused with horseflies due to their large size and loud buzzing when flying. They are most active in open habitats, woody edges, and forest glades.

Neotropical Region

Robber flies are diverse and can adapt to various environments, including the Neotropical region. While specific numbers aren’t available for this region, their strong adaptability likely results in a substantial presence.

Desert Climates

  • Resilient: Robber flies are known for their adaptability, making them capable of surviving in harsh desert climates.
  • Sun-loving: Robber flies prefer sunlit areas, allowing them to thrive in deserts where sunlight is abundant.

Woodland Areas

Robber flies can also be found in woodland areas. These sun-loving predators inhabit forest glades and edges, which provide ample opportunities for prey.

Comparison Table

Habitat North American Species Survival Features
North America Over 1,000 species Diverse habitats
Neotropical Unknown Adaptability
Desert Climates Unknown Sun-loving
Woodland Areas Unknown Forest glades

Predatory Behavior and Prey

Types of Prey

Robber flies are known to prey on a variety of arthropods, including:

  • Grasshoppers: A common prey item for robber flies due to their abundance and size.
  • Bees: These insects are targeted by robber flies due to their nutritional value.
  • Spiders: Although not as common, some robber flies will occasionally capture spiders.
  • Dragonflies: A more challenging prey, but still possible for robber flies.
  • Ants: Small insects like ants are often captured by robber flies.
  • Hymenoptera: This order of insects, which includes bees and wasps, is often targeted by robber flies.
  • Beetles: A diverse group of insects, beetles can also fall victim to robber flies.

Hunting Techniques

Robber flies use several strategies when hunting their prey:

  1. Aerial attacks: They catch their prey in mid-air, often using their powerful legs to snatch the insect.
  2. Ambush: Waiting on a perch until an unsuspecting prey passes by, the robber fly swiftly strikes.

Their predatory habits involve injecting their prey with neurotoxins and proteolytic enzymes, which paralyze and digest the prey, before the robber fly consumes them.

Predatory Impact on Insect Populations

The predatory activities of robber flies can have both positive and negative impacts on insect populations.

Pros:

  • Helps control populations of pest insects, such as grasshoppers or beetles.
  • Contributes to maintaining a balanced ecosystem by keeping prey populations in check.

Cons:

  • Can negatively affect populations of beneficial insects, like bees and other pollinators.
  • Possible disruption of food sources for other predatory species like birds, if robber flies consume too many insects.
Robber Flies’ Predatory Impact Pros Cons
Effects on Insect Populations Controls pest insects Negatively affects beneficial insect populations
Maintains balanced ecosystems Disrupts food sources for other predators

Mimicry and Defense Mechanisms

Mimics of Other Insects

Robber flies are known for their ability to mimic other insects. For example, some species of the genus Laphria mimic bumblebees by having similar patterns and colorations on their abdomens. They may also imitate other insects like butterflies and moths in order to deter predators.

  • Some examples of mimicked insects:
    • Bumblebees
    • Butterflies
    • Moths

Morphological Adaptations

Morphological adaptations in robber flies include features on their abdomen and legs that help them with predation and escaping predators.

  • Adaptations in legs:

    • Spines for capturing prey
    • Strong grip for holding onto potential predators
  • Adaptations in abdomen:

    • Tapered shape for better agility
    • Sexual dimorphisms in some species for easier identification

Comparison table of morphological adaptations:

robber flies butterflies & moths
Legs spines, strong grip slender, delicate
Abdomen tapered, agile wide, often colorful

In summary, robber flies rely on mimicking other insects and their morphological adaptations to avoid predators and capture prey. Their legs and abdomen play a crucial role in these defense mechanisms.

Reproduction and Mating

Mating Behavior

Robber flies exhibit minimal courtship behavior. Males pounce on females, resembling prey acquisition. Copulation occurs tail-to-tail, with the male and female genitalia connecting together.

Sexual Selection

Environmental conditions play a role in sexual selection for robber flies. Here are some brief characteristics:

  • Predators: All species prey on insects
  • Wings: Two wings per fly
  • Legs: Prominent spikes on legs
  • Body: Stout hairs on the body
  • Proboscis: Fashioned into a sharp tube or beak
  • Eyes: Large, widely-spaced compound eyes

These features enhance their predatory and mating capabilities, making them successful not only in hunting but also in finding a suitable mate.

Advantages Disadvantages
Mating * Quick mating process * Lack of elaborate courtship
Environmental * Adaptability to different environments * Predatory behavior sometimes limits mating time

Conservation and Biodiversity

Impact of Environmental Factors

Robber flies, belonging to the family Asilidae, are opportunistic predators that play a crucial role in maintaining biodiversity. Their population and behavior are affected by various environmental factors such as prey availability and habitat conditions. For instance:

  • In areas with higher prey availability, Florida Asilidae populations tend to thrive.
  • Habitat loss and fragmentation can negatively impact robber fly populations and their prey base.

Efforts in Conservation and Research

Several efforts focus on preserving and understanding robber fly biodiversity. Here are some examples:

  • Research: Ongoing studies aim to better comprehend robber fly biology and their role in maintaining ecosystem balance.
  • Habitat conservation: Initiatives that promote habitat preservation help sustain robber fly populations and support biodiversity.

Pros and Cons of Robber Fly Conservation

Pros Cons
Supports overall biodiversity May require resource allocation
Helps control pest populations Mitigation of potential drawbacks
Enhances ecosystem stability

In summary, the conservation of robber flies is essential for maintaining biodiversity and ensuring ecological balance. Through research and habitat conservation efforts, the preservation of these important predators can be supported.

Resources, Literature, and Identification Tools

Technology and Citizen Science

The identification of robber flies has become easier with the help of technology and citizen science initiatives. One useful resource is BugGuide, a website dedicated to insect identification from the Order Diptera and other orders. By uploading photographs of insects, users can obtain help from experts and other enthusiasts in identifying their finds.

Pros of using BugGuide:

  • Access to expert knowledge
  • Feedback from a community of enthusiasts

Cons of using BugGuide:

  • Might not always provide immediate results

Another helpful tool is the iNaturalist app, which uses AI technology to identify species within seconds, while simultaneously allowing users to contribute to global biodiversity databases.

Pros of iNaturalist app:

  • Instant identification using AI technology
  • Contribution to global biodiversity data

Cons of iNaturalist app:

  • Might not be as accurate as expert identification

Recommended Reading

For those interested in learning more about robber flies and their life cycle, the following resources are recommended:

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Dinner can be an Aphrodesiac for Robber Flies

 

Please tell me what this bug is
feel free to use this one too. It appears the female doesn’t really have her heart into what else is going on while she dines.
Ted

Hi Ted,
We can come up with several scenarios for this Robber Fly courtship. Perhaps he brought her a tidbit to keep her still, or maybe he moved in while she was dining. At any rate, there are future Robber Flies on the horizon which is good since they are lethal predators.

Letter 2 – Mating Robber Flies

 

Hi Daniel and Lisa Anne!
Hi Bugman!
AWESOME SITE AGAIN!!!!
I just can’t seem to stop looking at all of the beautiful pictures and excellent information!!!! Here are two Robber Flies engaging in Bug Love on my pepper tree. Enjoy!
Cathy

Hi Cathy,
We will proudly post your image on our Bug Love page.

Letter 3 – Mating Robber Flies

 

a couple of photos and a moth ID
Hello
I wanted to let you know I love the site, and have used it for many identification forays since we moved out to the country here in south central Kansas. I also wanted send you to the url for three of my recent photos. (they are larger than I like to send through E-mail) One is of a mating pair of robber flies, it was interesting to watch as the male will vibrate his wings while wiggling the females head with his front legs. One is a photo of a green moth I found on the front deck this last night and I would appreciate any help with the ID you could give me. The last if of a green grasshopper. I do not know the species, but considering the number of them again this year, the chickens will be getting quite fat.
Thanks again,
William Tong

Hi William,
Thank you so much for the great letter and photos. We are also very happy that you have used the site in the past. Quite frankly, we are getting a little tired of responding to desperate housewives with pantry beetles. Your green moth is a Virginia Creeper Sphinx, Darapsa myron. If you go to this USGS site, you might find it is not yet reported in your county. Perhaps you could report the siting. We are thrilled to have your Mating Robber Fly image for our brand new Love Among the Bugs page. Your grasshopper is immature and we do not recognize it.

Letter 4 – Mating Robber Flies

 

Robber flies
Dear Bugman:
Can you identify this pair of mating Asilids? Can you tell which is the female? I would assume the female is the one hanging suspended, since craneflies mate that way; also, with dragonflies it is always the male that holds fast to a perch, unless they’re doing it in flight. I am also attaching a photo of a single individual of the same species. The shots were made in early fall in a field of exotic grasses and thistle near a pond in the San Francisco Bay area. We have another larger Asilid at that pond that preys on damselflies, but I have not seen this species with a prey item.
Thanks very much.
Odophile

Hi Odophile,
We need to defer to Eric Eaton on anything more general than Robber Fly on this, though we agree the female is the suspended member of the pair.

Letter 5 – Mating Mantids and Mating Robber Flies

 

Bug Love submissions
I ran across your site as I was attempting to identify a fierce looking flying insect that I hadn’t seen before. Thanks to your site, I’ve identified him, and his 10,000 friends as “Robber Flies”. As I was taking a picture to submit, a couple of the rascals saw the camera and thought they would try out for “Bug Love”. I thought it was a little unusual, because all the other pictures I’ve seen of them mating was tail-to-tail, unlike these two exhibitionists. I’ve also included a shot I took last year of a couple of Mantids. I had about 3 of them which I kept as “free range” pets. I guess they liked it here, because they stayed all season. Enjoy!
Jeff King
Krum, TX

Hi Jeff,
What wonderful images you have provided for our readers.

Letter 6 – Mating Robber Flies

 

What in the World!!! Please Help!
Dear Bugman,
I found your site about two months ago after being pinched by a beetle. Great photos, and descriptions=hours of fun. Anyway, these guys were flying around having a good time scarring my niece. I haven’t seen any like this before (we live in Central Illinois). I looked through your pages on bees, wasps and dragonflies, but couldn’t find a match. Any help would be much appreciated (and also end a family discussion on the bugs identity)! Thank you, keep up the great work and have a great day!!!!
Kim B.

Hi Kim,
Your mating insects are Robber Flies in the family Asilidae, possibly Giant Robber Flies in the genus Promachus.

Letter 7 – Robber Fly

 

beetle bug
My brother sent me this photo a couple years ago to ask if I knew what it was. I had no idea at the time that there was a website (yours) that I could consult. Now I know. He lives in London, Ontario, and the subject was photographed on a paper plate. I don’t see any antennae but there are 6 legs. And then there is a long component extending from the rear end. I have seen subjects with ovipositers on your site – is that was this is or does it have something to do with wings? I don’t remember if he said anything about flying. Can you tell me what it is?
Paula
PS I have already spent hours going through your website looking for this subject and have not seen everything – nevermind reading all the emails!

Hi Paula,
This is a Robber Fly and we actually have an entire page devoted to them. We usually get photos in the summer and that is a good time to see them on our home page. We also have many images of them mating. That is the abdomen extending beyond the wings.

Letter 8 – Robber Fly

 

Hi, can you help me identify this fly?
Hi, My name is Cary and I found a fly that I cannot identify. I live in the Orange County area of Calfornia. As I began walking to my car to leave the beach, I noticed a fly on the wall. It was about 1.5" long and at first glace, it looked like a dragonfly because of the large hump on the back of the head and the long abdomen but the wings were not perpendicular to the body; they were laid back like a regular fly. To my surprise, I put my finger in front of it and it held on so i walked to my car with this fly on my finger and managed to drive all the way back home so that i would be able to take pictures of it. I hope that these pictures are good enough for identification. If you would like, I can also send a short video if it as well.
Thanks,
Cary

Hi Cary,
You have sent in a photo of a Robber Fly from the Family Asilidae. They are swift flying predators that pounce on resting insects from above. We would have loved to see the photo of the Robber Fly on your finger. They have keen eyesight and are very difficult to approach since they are quick to take flight.

Thanks for your help and quick reply! I was reading around about the robber fly and I learned that it has a proboscis which could inject a toxin into its prey, which then dissolves the meal internally, which then gets sucked up by the big fly. Sounds as if it were a flying spider! The experience really makes me think about how many oppertunities it had to sting me but didn’t. Very cool!
Thanks again,
Cary

Letter 9 – Robber Fly

 

BugMan,
I am hoping you can help me identify this bug. I have had several of them flying in my house and one has stung me (At least I think it was one like this, got me on the back of the neck, and since I did not see it and this is the only flying bug I have seen in my house I have given it the blame.) I know this is a picture of a dead bug and I really strive not to kill bugs but it was flying around in my daughters room and she would not calm down (4 years old would not stop crying) until it was dead and she could see it. So needless to say I was forced to kill it so I could sleep (Does this make me a bad person?). I live in Essex, MD, it was about an inch and a half long, 6 legs, long slender tail, big bug eyes, and 2 small antenna on its head (1mm maybe 2mm), one set of wings that were tan from top to bottom with only supports throughout no other coloring, and a small roundish buldge on the top of its back above the wings with stripes of brown and black. I am attaching 3 pictures to see if you can help identify it. Thanks for all your help.
Sincerely,
Matthew Rebbert

Hi Matthew,
Your insect is a Robber Fly, Family Asilidae. The adults are predatory, and are important in the control of many insect pests including Grasshoppers. The Robber Fly will attack insects much larger than itself. They are capable of inflicting a painful bite if carelessly handled, but they do not normally bite people. Robber Flies often find their way into homes. We would recommend trapping it in a glass when it alights on the window, and then releasing it. Show your daughter that the fly was taken outside so it could kill other bugs. Eric Eaton adds “Your specimen of Robber fly (reddish-yellow with black stripes) are Diogmites sp., the Hanging Thieves,” named for the way they suspend themselves from one pair of legs while feeding on a prey item.”

Letter 10 – Robber Fly

 

Strange Flying Bug in Yard
Mon, Jun 22, 2009 at 9:16 AM
Flying insect. Looks like it is laying eggs. Fly type body, wasp like wings, has design on body like bee. Looked like a giant mosquito to me. Made deep buzzing sound as a warning when I got too close. Never saw one before.
the bug guy
Tucson, Arizona

Robber Fly:  Efferia rapax???
Robber Fly: Efferia rapax???

Dear bug guy,
This is a Robber Fly, and we believe it is in the genus Efferia. There is a photo of Efferia rapax posted to BugGuide with numerous comments. That photo looks very similar to your specimen, and it is also from Arizona. It would really take someone far more qualified than we are to properly identify what species of Robber Fly you have.

Robber Fly:  Efferia rapax???
Robber Fly: Efferia rapax???

Letter 11 – Robber Fly

 

Huge unknown wasp looking bug
August 28, 2009
The other day I was launched into action as screams came from the kitchen. “Daddy come get this bug it’s HUGE!!!” So I did what Dads do and got it but now I would like to know what in the world it is… I’m 37 years old and lived in Arizona my entire life and have never came across anything like it. This bug was HUGE. I would have to say larger than a silver dollar. I forgot to put something like a quarter in the picture to get reference as to size but believe me… HUGE…
Thank you for your time
Daddy Matt
Sierra Vista, Arizona

Robber Fly
Robber Fly

Hi Daddy Matt,
In the past year, both we and BugGuide have gotten several reports of this majestic Robber Fly, Archilestris magnificus, from Arizona.  Prior to that, the species was known from Mexico.  Robber Flies are predators, and they might bite humans if carelessly handled, but they would need provocation to bite.

Letter 12 – Courting Robber Flies from Texas: Heteropogon patruelis

 

Saw this (possible) mating ritual…
November 24, 2009
Although I saw the two bugs interacting for some time, I have no idea what they are after having looked here and there for an answer.
Stingrey
Big Bend National Park

Robber Flies
Robber Flies

Hi Stingrey,
These courting Robber Flies are gorgeous.  The male is flying.  We believe they are in the genus Laphria, but we cannot find an exact match on Bugguide.  The closest is Laphria trux but it has black legs, not red ones like the individuals in your photo.  Last week we got assistance from an expert in Robber Flies, Dr. Robert A. Cannings, Curator of Entomology from the Royal British Columbia Museum.  We are writing to him again for assistance.

Hi Daniel:  I’m sure this is a Heteropogon. There are a number of
species in Texas (and I’m not familiar with them) but this may be H.
patruelis, which is relatively big and has a red abdomen. I’ve sent the
photo to Eric Fisher to see if he can help.
Rob

Update from Robert A. Cannings and Eric Fisher
November 30, 2009
Hi Daniel: Here is Eric Fisher’s reply about the Heteropogon. There’s no one better at identifying most NA asilids, so I doubt if you’ll get a better answer.
Cheers,
Rob

Hi Rob,
Yes, this courting pair do look like Heteropogon patruelis — especially in overall coloration. Only puzzling thing is I can’t really see signs of the patches of erect black & white hairs on the midlegs of the male (I assume the extended legs are the fore pair, and the dangling ones are the midlegs; hard to tell because the leg-base area is so dark).
… Cheers,
Eric

Letter 13 – Mating Robber Flies

 

Mating Robber Flies
February 26, 2010
Hi, WTB,
Mating Robber Flies.  Mid-July, 2009.  Foothills of the Santa Rita Mountains, southern Arizona, about 4,400′.  There are lots of Robbers around here, and I’m always glad to observe them.
Best,
Denny

Mating Robber Flies

Hi Denny,
We believe these may be Neomochtherus californicus, a species of Robber Fly that is represented on BugGuide with a single series of three images, though we would need to defer to a Diptera expert, or better yet, a Asilid expert, for a conclusive identification.

Robber Flies Mating

Letter 14 – Mating Robber Flies

 

Is this a robber fly?
July 6, 2010
I see these strange bugs in my friend’s garden all the time. I have pictures of one of them eating a moth. I have looked thru your pictures and believe this must be some kind of robber fly. They are very creepy looking.
Veronica
Crossville, TN

Robber Flies Mating

Hi Veronica,
You have submitted some images of Robber Flies feeding, but the image we have chosen to post appears to be of a pair of Robber Flies preparing to mate.  We are uncertain of the species of Robber Fly you have photographed.

Letter 15 – Robber Fly

 

Bug from the End Times
Location:  Bend, Central Oregon
July 23, 2010 5:07 pm
Good afternoon Bugman! I have enjoyed your site thoroughly for some time and thought of you when I began being plagued by these bugs. I live in Bend, OR and we have had tons of these creepy looking flies around lately (July-ish). They are about 1/2”, maybe a bit longer, and seem to especially be prevalent on hot, dry days. They look like something from the end times, and my first inclination is to kill them. Especially when they land on myself or my infant. (They give me the evil eye- I’m assuming they’re doing the same to the bubs.) However, before declaring war, I want to know what they are. (After scouring your site, I’m guessing maybe a Robber fly???) Whenever I look up flies in Central Oregon I get a lot of pictures of fly fishing. Not helpful. What are these evil looking bugs, and are they harmful? Should I interrupt the bug-lovemaking in the future to decrease their population?
Thanks for your time and help!
Bugged

Mating Robber Flies

Dear Bugged,
You are correct that these are Robber Flies in the family Asilidae, and it appears the pair in one of your photos is mating.  We would recommend that you learn to tolerate them.  Whatever small annoyance they bring you is probably greatly outweighed by the advantage of having them prey upon undesirable flying insects, like mosquitoes and disease carrying flies.  We don’t believe we will be able to provide you with a species name, or even a genus name, because there is not enough detail in your images, and Robber Flies can be somewhat difficult for us to properly identify even under the best of conditions.

Robber Fly

Thanks for your help! I will leave them be in the future, and perhaps not be so freaked out by them now that I know what they are! You will be happy to know I rescued one just earlier today from the bub’s wading pool where I’m assuming it stopped by for a drink. Or perhaps a refreshing swim.
Next time one lands on me, I will be sure to thank them for controlling the fly and mosquito population in my area.
And thanks for the time and effort you put into the website. Over the years I’ve developed an unhealthy interest in studying spiders, and your site has helped me learn to appreciate even more bugs. They really are pretty cool when it comes down to it.

Thanks for the update.  We would like to add a precaution to our earlier response.  You most likely have nothing to fear should a Robber Fly land on you, but swatting them may cause them to bite.  You should exercise caution when trying to handle any predatory species.  Should you be bitten, though, there is no cause for alarm as Robber Flies do not have venom.

Letter 16 – Robber Fly

 

Strange fly
Location: Daytona Beach, FL
March 9, 2011 10:41 pm
I was at work and noticed this very odd looking insect. It appears to be some sort of fly though I haven’t the faintest idea what type. Forgive the low resolution photo, it was all my phone could muster.
Signature: Brian B

Robber Fly

Hi Brian,
Your photo does not have enough detail for us to be able to determine a species, however, the silhouette alone allows us to identify this as a Robber Fly in the family Asilidae.  Robber Flies are very adept hunters.

Letter 17 – Mating Robber Flies

 

What kinda bugs are this pair?
Location: Jacksonville, Florida
June 1, 2011 9:47 pm
Hi, I took this picture today thru the screen of our lanai. The bugs are doing the love dance and stayed that way for at least an hour. We live in Jacksonville, FL where the weather today was a steamy 89 degrees. I have never seen these bugs before, not flying, not crawling; not at all. I did post it on Face Book where someone thought it was a locust, but I looked at pix and their legs are not that long. Would love to know what this pair is. We’ve seen all kinds of creepy crawly things in Florida, this is a new one for us. Thanx for your help.
Signature: Warm Regards, Sunnie Ellis

Mating Robber Flies

Hi Sunnie,
These are mating Robber Flies.  We will be out of the office for a week and we have prepared your posting to go live next week in our absence.

Letter 18 – Robber Fly: Archilestris magnificus

 

Here’s a Mexican Robber Fly for your files
Location: Douglas, southeast Arizona
September 23, 2011 2:44 pm
Howdy…finally got this insect identified from your website. We live 8-9 miles from the Mexican border and have these visitors quite often. Surprised that just a couple years ago they were rare in the US. They’ve all been camping out here:) Used to confuse them with the Tarantula Hawk, but not anymore! They hang out around our many Jujube (Fig) Trees in the spring and summer. Don’t bother with us at all.
Signature: Lori – Arizona

Robber Fly

Dear Lori,
Archilestris magnificus is such a gorgeous Robber Fly.  On the rare occasions we receive photos of them, we immediately post them.  When we first posted a photo in 2007, it created quite a stir.

Letter 19 – Bug of the Month September 2013: Mating Red Footed Cannibalflies

 

Subject: What are these things
Location: MD
August 30, 2013 3:10 pm
Okay these 2 are definitely we think matting but what are they. These were seen in MD on a wooden swing.. if that is any help. Thank you,
Signature: Edie

Red Footed Cannibalflies Mating
Red Footed Cannibalflies Mating

Dear Edie,
These are mating Giant Robber Flies in the genus
Promachus, and we believe they might be Red Footed Cannibalflies or Bee Panthers, Promachus rufipes.  We are not entomologists and there is not enough detail in your photographs to be certain, but we believe based on the markings, our identification is most likely correct.  You can compare your photos to those posted to BugGuide which reports:  “Preys on large flying insects. Has been reported to attack Ruby-throated Hummingbirds” with a link to the Hilton Pond Center website.

Letter 20 – Mating Robber Flies

 

Subject: Ichneumon Wasp?
Location: West Milford, New Jersey
July 3, 2014 6:48 am
I have looked at lots of pictures, but I cant ID this insect. I have seen them in my garden a few times, I feel like it may be a Ichneumon Wasp, but I have been unable to match anything with the dark band/stripe down the middle of the thorax.
Signature: Geoffrey Syme

Mating Robber Flies
Mating Robber Flies

Hi Geoffrey,
These are mating Robber Flies in the family Asilidae.  We will attempt to identify the species.  Based on images posted to BugGuide, this appears to be
Asilus sericeus.

Letter 21 – August 9, 2014 is the Day of the Robber Flies: Fourth Red Footed Cannibalfly posting today, bringing total to six large Robber Fly Postings!!!

 

Subject: Very large bee insect
Location: Cumming, ga
August 9, 2014 4:00 pm
Hello,
The attached picture looks like a very large bee, but it has long legs, flies, has a furry ruff around it’s neck and was on my green car side view mirror the other day. I’ve never seen anything like it.
Signature: Marisa

Red Footed Cannibalflies
Red Footed Cannibalflies

Hi Marisa,
This is the fourth image we are posting today of a Red Footed Cannibalfly, a large predatory Robber Fly, including one image of a mating pair of Red Footed Cannibalflies.
  Add to that two images of Hanging Thieves, another type of large Robber Fly, and that makes a total of six Robber Flies posted today.  We are declaring today the Day of the Robber Flies.

Letter 22 – Mating Robber Flies

 

Subject: Huge crazy fly
Location: McKinney, Texas
July 23, 2015 7:50 am
I went outside and heard an amazing ruckus in the bushes and found two of these very large, hairy, long, and huge-eyed flying buggers mating with each other. They look rather fierce and I’m not sure if they are a type of dragonfly? The picture shows the front of one of them, still attached to the other. Since they are obviously busy, I didn’t want to get too close or to be too intrusive!
Signature: Lover of bugs, Michelle

Mating Robber Flies
Mating Robber Flies

Dear Michelle,
There is not enough detail in your image to be certain, but we believe your mating Robber Flies may be Red Footed Cannibalflies.

Thank you so much!  I clicked the link to your site and that is exactly what it is.
And thank you for all you do.  I just love your site!

Letter 23 – Mating Bee-Like Robber Flies

 

Subject: possible robber fly
Location: Plainsboro NJ
June 9, 2017 4:54 am
Greetings:
The small eyes and short antenna have me thinking this is some sort of bee-mimic. I saw some pictures of robber flies that look a little like this. Can you tell me if this is correct, and maybe narrow it down to a species?
And I suspect they’re having sex; does that sound right?
Found a weekend ago: June 3.
John
Signature: jpviolette

Mating Bee-Like Robber Flies

Dear John,
Your request arrived on the first day of our holiday and we are currently trying to post some of the best images that arrived while we were out of the office, and that includes your image of mating Robber Flies in the genus
Laphria, the Bee-Like Robber Flies.  Many species in the genus look similar, but we believe your individuals might be Laphria virginica based on images posted to BugGuide where they are described as:  “Easy to confuse with L. flavicollis. The main gestalt things to look for are the hairiness of the black abdomen, very fuzzy in virginica but somewhat glossy in flavicollis. The golden hair on the top of the thorax looks more swept back and finely constructed in flavicollis. And in virginica, the legs have a reddish brown tone to the fuzz in good light. –Herschel Raney, 4.v.2006.”

Greetings:
Thanks – I’m glad I was on the right track. I’ve gotten fairly good at recognizing some of my area’s more distinctive butterflies/dragonflies, but I have a much harder time with these guys (especially mimics).

John

Letter 24 – Robber Fly

 

Subject:  Flying insect
Geographic location of the bug:  massachusetts,  USA
Date: 07/13/2018
Time: 03:40 PM EDT
Your letter to the bugman:  Hi, there’s a bunch of these flying around. They seem to enjoy sitting in one place for a long time or sunbathing. Was having trouble identifying it.. But very curious about it.
How you want your letter signed:  Michal

Robber Fly

Dear Michal,
This is a beneficial, predatory Robber Fly and the ovipositor indicates she is female.  She uses her ovipositor to lay eggs and cannot sting with it.  Based on this BugGuide image, we are confident your Robber Fly is in  the genus
Efferia.

Letter 25 – Robber Fly

 

Subject:  What is this in my garden?
Geographic location of the bug:  Zone 8a DFW Texas
Date: 07/20/2019
Time: 03:14 PM EDT
Your letter to the bugman:  I was out just a bit ago and saw this, not on a veggie plant but on a stake. Never seen anything like it!
How you want your letter signed:  Terry

Female Robber Fly

Dear Terry,
Before we were able to view your image, we guessed correctly that you wanted a Robber Fly identified, and Texas has some huge ones, including the Belzebul Bee-Eater.  Your individual is a female based on the stinger-like ovipositor, and we believe she is in the genus
Efferia.  Aerial predators like Robber Flies and Dragonflies frequently rest on sticks and dead branches.

Thank You! I saw another 2 yesterday. Worried cuz I don’t have many bees in the first place.

Letter 26 – Robber Fly

 

Subject:  Prehistoric Wasp-ish Bug Creature ID
Geographic location of the bug:  Leming, TX, USA
Date: 07/08/2020
Time: 08:25 PM EDT
Your letter to the bugman:  Dear Bugman, I have seen the attached waspish creature here in the Texas Brush Country in summers past. It’s about 1.5-2 inches tall, and it looks like it’s wearing a fuzzy sweater vest. Just seems to sit there and stare at me, hence the desire to know something about my observer. Thanks a bunch in advance, Bugman.
How you want your letter signed:  Debbie LV

Robber Fly: Possibly Saropogon hypomelas

Dear Debbie,
This is one impressive predatory Robber Fly, and Texas has its share of giant Robber Flies.  We believe your individual is in the genus
Saropogon, possibly Saropogon hypomelas which is pictured on BugGuide.

Hi Daniel, WOW! I am so glad to know we have an obviously well-fed beneficial! That eats grasshoppers and grasshopper eggs! I will be sure to express appreciation instead of abject fear when next we meet.Thank you so much for your reply.

Letter 27 – Robber Fly

 

Subject:  Large robber fly
Geographic location of the bug:  Pasadena Ca
Date: 07/23/2021
Time: 05:19 PM EDT
Your letter to the bugman:  These photos are taken around a backyard pond in Pasadena Ca. Although I would like to know what species the dragonfly is (it has just emerged and is still clinging to it’s niad shell) my main qestion is in regards to the other photo. What kind of robber fly do you think this is? It’s by far the largest one I’ve seen. The plastic cap of the garden stake next to it is 19 millimeters in diameter.
How you want your letter signed:  Roy

Robber Fly

Dear Roy,
Based on images posted to BugGuide and the reported range, we believe your Robber Fly might be
Promachus princeps.

Letter 28 – Robber Fly

 

Subject:  Creepy Critter I’ve Never Seen Before!
Geographic location of the bug:  Madison County, Kentucky
Date: 09/09/2021
Time: 11:26 PM EDT
Your letter to the bugman:  My boyfriend and I walked into the kitchen around 10:45 pm and next to the sink was an insect I was creeped out by, but couldn’t stop looking at!
It didn’t move when the boyfriend removed it to the bathroom. I am not sure if it was dead or alive.
Both of us have lived in old houses before and never seen one….we are both in our 40’s.
The house we live in now in on the foothills of the Appalachia Mountains. It was built in the late 1800’s and renovated in the 1940’s and again in the 1960’s.
The original creek rock, used in original foundation, is still under the house.
There are also many caves around the area. As well as other “creepy” types of bugs. Example…. Cave Crickets.
The weather has been a lot milder, wetter, and, cooler than normal.
Are these normal for this area? I can’t find anything about them.
Thanks so much!
How you want your letter signed:  Concerned in Kentucky

Robber Fly

Dear Concerned in Kentucky,
You have no cause for concern.  This is a Robber Fly, a winged predator that did not originate from inside your home.  It likely accidentally entered the home and died.  This is an outdoor predator that has no interest in living indoors.  We cannot tell the species for certain but we believe it might be a Hanging Thief in the grnus
Diogmites which is pictured on Bugguide.

Authors

    by
  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

    View all posts
  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

    View all posts

5 thoughts on “Robber Fly Life Cycle: A Fascinating Journey Explained”

    • Different species of large robber flies are found throughout North America, though the Southwest seems to have the most diversity.

      Reply
  1. I saw a mating pair fly up today (in Antioch , TN) and came here to identify them. Funny that they were the highlighted bug of the day! Thanks! If you need more photos I got a great shot of them mating.

    Reply

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