Do Mydas Flies Bite? The Truth Behind These Spider Wasp Lookalikes

If you live in the western parts of North America and spot a large, wasp-like fly, look closer – it might be a Mydas Fly. But do Mydas flies bite or sting? Let’s find out.

Mydas flies are fascinating yet harmless creatures who do not bite or sting.

They don’t even have a stinger, but they imitate having one for the benefit of their potential predators to protect themselves.

However, they look quite intimidating to us due to their wasp-like appearance, a kind of Batesian mimicry they have adopted as a defense mechanism.

Continue reading to learn more about Mydas, their eating habits, and why having them around is actually good for us.

Do Mydas Flies Bite
Mydas Fly

What Are Mydas Flies?

The Mydas fly belongs to the Diptera order, meaning it is a two-winged bug (two pairs of wings, to be more precise).

There are about 471 species of Mydas flies around the world. They belong to the Mydas Clavatus club,  a relatively small fly family.

The name, interestingly, comes from the famous King Midas, who received the gift of turning anything to gold on touch. The golden band on these flies’ abdomens is what references that legend.

Adult flies are quite big, and their appearance often intimidates those around them. The largest fly in the world, Gauromydas heros, is a part of the same family. It has a massive wingspan of about four inches.

People who have seen these flies naturally wonder whether Mydas flies are dangerous. The answer is no – these are just gentle giants of the fly world.

Even though they may look like spider wasps (who are infamous for their painful bites) from the outside, Mydas flies are completely harmless.

Do Mydas Flies Bite
Mydas Fly

Do Mydas Flies Bite or Sting?

Mydas flies do not bite or sting – they are flies, and they don’t have a stinger! They are a Batesian species (named after the19-th century biologist Henry Walter Bates), which mimics the wasp family.

They resemble their intimidating appearance to ward off predators.

Since they have a small family compared to other fly families, they are not seen very often. So, when people spot them, they get alarmed by their large size and dramatic appearance.

They may even try to fool you into thinking that they are stinging insects by waving their hinds around. All of this is a big show to protect themselves from a potential predator.

Do Mydas Flies Bite
Mydas Fly

Is There Any Way In Which They Are Beneficial?

During their larval stage, the young fly is a soil-dwelling predator who eats up grubs like beetle larvae and white grub worms.

In this way, it contributes to keeping the garden pest-free.

It is thought that the winged adults also feed upon flies, caterpillars, and other bugs, but there is little evidence to support the same. So, for now, the Mydas fly larvae save the world as a biocontrol agent.

What Do They Eat?

Some experts claim that Mydas flies can prey on other insects, but there is little evidence to prove this.

They can often be seen hovering over the flowers of the rattlesnake master plant in North America, which suggests that they might feed on pollen from the flowers.

On the other hand, their grub-like larva is known to be a soil-dwelling predator. In this stage of their lives, these flies eat decaying insects and grubs, like beetle larvae.

Do Mydas Flies Bite

What is The Habitat of the Mydas Fly?

Mydas flies are native to North America and prefer to live in temperate climates. About 51 species of Mydas flies are found here, most of which are located in the western states.

These flies are active during the late spring season. You can spot them flying in parks, gardens, woodlands, forests, knolls, etc., along with other houseflies.

These insects are slightly clumsy fliers, always bumping into things.

Frequently Asked Questions

Where does the Mydas Fly live?

About 51 species of Mydas flies are native to North America and can be found in the western parts of the continent. They prefer warm climates and spend their adult lives in parks, gardens, woodlands, forests etc, just like most other flies.

How big can Mydas flies get?

Mydas flies are unusually large flies. They can grow to be anywhere between ¼ to 1¼ inches. Their size and appearance also resemble robber flies and spider wasps,  making them look intimidating to a casual observer.

What is the largest fly?

The largest fly in the world is known as Gauromydas heros. It comes from South America and has a four-inch wingspan. Gauromydas hero, as the name suggests, is also a part of the Mydas fly family.

What’s the biggest fly in North America?

Crane flies are the biggest fly in North America right now. They have a wingspan of about 2.75 inches, and in appearance, they resemble giant mosquitoes.
Since they look similar to mosquitoes, these flies are also known as mosquito hawks or daddy-long-legs.

Wrap Up

Mydas flies do not have a stinger and cannot bite. They are, in fact, beneficial insects that feed on grubs and pests that are known to damage crops in their larval stage.

So, the next time you spot a Mydas fly, don’t be intimidated by its imposing appearance, and get closer to have a better look!

Thank you for reading the article!

Reader Emails

The appearance of these flies has often caused alarm among all those who see them. Over the years, many of our readers have shared their experiences with these flies with us.

Go through these first-hand experiences, and you will figure out that the bug is pretty harmless, and what’s more – it photographs very nicely!

Letter 1 – Katydid and Mydas Fly

 

Hi bugman!
First, I must tell you.. I love your site – fascinating stuff! Second, I have two bugs I can’t identify. Bug1 is a huge scary looking thing (to me anyway) 2 to 2.5 inches long at least. Bug2 is very pretty.. I love the long legs and antennae. Can you help? I live in Northern Virginia (Fauquier County) about 50 miles west of DC near the Blue Ridge Mountains. Thanks for your time!!
Danette Jennings

Mydas Fly Katydid

Hi Danette,
Your first insect is a Mydas Fly. Adults are predatory, feeding on caterpillars, flies, bees and Hemipterans. Your other insect is a female Katydid.

Letter 2 – Mating Mydas Flies

 

Mating Wasps Location: Royal Oak, Michigan July 25, 2011 6:19 pm Dear Bugman, Over the past couple of weeks (beginning mid-July) this guy has been seen flying around the yard and never let me approach closely enough for a photo. Until he became preoccupied… It becomes startled easily, but sits for long periods of time on the mulch in my garden, rarely landing on the plants. It’s about 1.5” long. It resembles some of the spider wasps or wood wasps, but I was a little overwhelmed trying to identify it myself. Thanks! Signature: DaleShannon
Mating Mydas Flies
Hi Dale, These mating Mydas Flies, Mydas clavatus, are excellent wasp mimics.  You may read more about them on bugguide, where it is indicated:  “Mating system in this species unknown. Different Mydas species apparently have different mating systems, including resource-defense polygyny and ‘hilltopping’.”  BugGuide does have at least one image of a mating pair.
Mydas Fly

Letter 3 – Mating Mydas Flies

 

What Do Mydas Flies EatSubject:  What kind of bug is this? Geographic location of the bug:  Fallsburg, Ohio Date: 07/30/2018 Time: 08:28 PM EDT Your letter to the bugman:  A friend asked for my help in identifying this insect. I’m not sure what it is and I’m curious as well because I saw one last week in Pataskala, Ohio. Thanks How you want your letter signed:  However
Mating Mydas Flies
These mating Mydas Flies are identified as Mydas tibialis on BugGuide.

Letter 4 – Mydas Fly

 

Mydas Fly
WTB,
I have had this huge flying insect run me out of my flower beds for the past couple of years. I saw it attack a Digger Wasp in my vegetable garden last year! I am pretty sure it is a Mydas Fly, but I would like to know a little bit more information on it. What does it do? Does it sting? LOL
Monica Ragsdale



Hi again Monica,
This is a Mydas Fly, Mydas clavatus. The adults are predatory, feeding on caterpillars, other flies, bees and true bugs. I guess with your observation, we can add wasps to the menu. Also, your photo implies that they also feed on nectar which many flies do. Larvae live in rotting wood and probably feed on beetle larvae. Flies do not sting, but they will probably bite if mishandled.

Letter 5 – Mydas Fly

 

Scarab hunter wasp? May 21, 2010 Never seen anything like this intimidating looking insect. Maybe close to two inches long? It looks similar to those published on your website…. Ben Port Charlotte Florida
Mydas Fly
Hi Ben, This is a Mydas Fly, Mydas clavatus, and you can read more about Mydas Flies on BugGuide.  Your observations are astute.  A Mydas Fly, according to BugGuide:  “Resembles a wasp of the family Pompilidae, and is presumably a Batesian mimic.”  BugGuide also indicates:  “Mydas larvae prey on beetle larvae, esp. those of June beetles.

Letter 6 – Mydas Fly

 

Large black flying insect Location:  Northern Indiana August 1, 2010 4:23 pm Today I found this insect dying in my yard in northern Indiana. Ants were busy foraging on it. I could only see one pair of wings. I’ve never seen anything like this one before! Nick
Mydas Fly
Hi Nick, This is a species of Mydas Fly, Mydas tibialis, which we identified by matching your image to photos posted to BugGuide.  According to our Audubon Society Guide to North American Insects and Spiders:  “Only a few species of mydas flies occur in North America.  … The adults are predatory and closely resemble wasps and robber flies.”

Letter 7 – Mydas Fly

 

Subject: What is this insect? Location: Oxford, NC June 22, 2012 12:50 pm Hi, I am hoping you can help me identify this insect. I don’t think I have ever seen these before. It looks similar to a peach tree borer moth, but I don’t think their behavior makes sense if that is what they are. I have been watching several of these flying around an area where I have spreading chipped wood mulch. They appear to be laying eggs in the mulch, and there are no peach trees around at all. Thanks for any help. Signature: Dan
Mydas Fly
Hi Dan, It is interesting that you have compared this Mydas Fly to a Peach Tree Borer because both insects are wasp mimics.  According to BugGuide:  “Eggs are laid singly in soil or rotting wood. (See video of oviposition–Flickr). Mydas larvae prey on beetle larvae, esp. those of June beetles. Larvae pupate close to soil (or wood?) surface. Adults are active only in mid-summer.” Thanks very much!  That is definitely it.  I hope they also prey on Japanese beetles.

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.

  • 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.

6 thoughts on “Do Mydas Flies Bite? The Truth Behind These Spider Wasp Lookalikes”

  1. Found a mydas tibialis a few years ago and had a difficult time IDying it also. I was told that there aren’t many known populations of this insect in the midwest. I’m a naturalist at Rum Village park in South Bend, IN, (northern IN). Where in Northern IN are you, Nick? I noticed that another mydas tibialis photo was also posted from northern IN.

    Vince

    Reply
  2. Well, they definately had me fooled! I was sure this was a type of spider wasp. The courtship was intense as well – they began chasing each other around, flying in circles and clinging to each other. I thought it was a territorial battle, and sounded like a small scale WWII dog fight! Thanks again.

    Reply
    • Thanks so much for your first hand observations of the mating habits, which according to bugguide, are not well documented.

      Reply
  3. Hi -I live in Tampa,FL and today saw a very LARGE wasp looking bug in the grass. Had to be 1-1/2-2″ across. totally black but had a blood red band around the middle. the Mydas fly looks to have an orange band??. Couldn’t get a picture because being a girlie-girl, I ran inside! Had large wings as he was moving around (I was in the screened room). Any ideas? PS your website it awesome and so informative. Thanks for any info. this is the first one I’ve ever seen in Florida. Hugs…..

    Reply
    • You may have encountered a Mydas Fly, but since the Mydas Fly is a mimic of wasps, you may have also encountered a Spider Wasp like this individual on BugGuide or a Digger Wasp, also represented on BugGuide. You may also read more about Mydas Flies on BugGuide.

      Reply
  4. I’m in Abuja, Nigeria… west Africa. This is the first time seeing this… they are a lot under my staircase… it’s soooo scary! I sprayed one that was trying to attack me with insecticide and it was adamant… became more aggressive in its attack as I kept running away and screaming for help. I have a video of it when it finally died! I had to search what this may be.. I have 2kids; i
    So scared!

    Reply

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