Aerodynamically bumblebees aren’t supposed to fly, but they do it anyway. Hoverflies do something even more amazing: they hover! But why do hoverflies hover, and how do they do it? We explore the science behind insect flight in this article.
It is quite rare to come across phenomena that break the laws of science.
The flight of the hoverfly is one such case that defies the conventional laws of aerodynamics that holds true to flights, helicopters, and more.
How? Let us find out.
How Many Types of Hover Flies Are There?
Flower fly populations are abundant worldwide. You will be fascinated to know that there are approximately 6,000 species of hoverflies globally.
They can adapt well to various climatic conditions, which is why you can find them in all regions except Antarctica and deserts.
Also, 62 hoverfly species are found in America. You can spot them in Ohio, Pennsylvania, Kentucky, West Virginia, and many other states in the US.
Adult hover flies prefer to be around flowering gardens as they are the ideal sites to provide primary food sources like nectar and pollens.
They like to lay their eggs in places that are infested with aphids, so if you have both things in your garden, then it is likely that you will find hoverflies.
Do All Species Hover?
Almost all hoverfly species can be spotted actively hovering over a wide range of flowers.
Since they are active flower visitors, they are often considered excellent pollinators.
Also, the hover fly larvae are ferocious predators of aphids, scale insects, and other soft-bodied arthropods.
Due to this, farmers use these bugs for biological control of aphid infestations. A bunch of larvae can comfortably eradicate entire aphid colonies in days.
No wonder why they are called beneficial insects.
Why Do Some of Them Hover?
Hoverflies get their name because of their ability to stay suspended in the air during flight, like a drone. But not all of them hover.
There is a particular species of hoverfly that are called drone flies.
A drone fly is an excellent mimic of a Honeybee. They, too, have bee-like black and yellow stripes on the abdomen.
These drone flies hover around the flowers to be able to feed efficiently.
However, hovering also helps them attract mates.
Research has shown that the stability and duration of the hovering help to attract the female. The more steady they are in mid-air, the more the chances of impressing a mate.
Also, these insects will keep hovering around you if you are drenched in sweat.
This happens because hoverflies are particularly attracted to the salts in human sweat and fall on the skin to lick them.
How Do Hoverflies Fly?
The hovering ability of hoverflies is one of the most interesting facts about them.
These flies constantly keep adjusting the frequency of their wingbeats to the wind pattern to stay afloat during windy days. How amazing is that?
A strong gust of wind cannot blow away a skilled hoverfly.
On rare occasions, you can also spot them around flowers flying backward.
The primary reason behind this is the flexible pair of wings. Hoverflies have one of the most flexible wings in the insect kingdom.
The versatile nature of their pairs of wings is off the charts; they can bend and twist these wings at a 45 degrees angle and at a frequency of 300 Hz.
These wings help to maintain the perfect angle to be able to hover.
Leading Edge Vortex
According to the laws of conventional aerodynamics, insects like bumblebees and hoverflies are not supposed to be able to fly.
The leading edge vortex is a process that allows these insects to fly. It is this process that helps these insects to defy the laws of aerodynamics.
As the name suggests, a vortex is created along the leading edge of their wings; This creates a low-pressure zone on top of the wings.
As per Bernoulli’s theorem, the low-pressure zone adds an upward lift that helps them fly.
Another reason insects like bumblebees and hoverflies can fly is because of the viscosity in the air.
Viscosity adds resistance when these insects beat their wings.
The dragging action involved sweeps more air which results in higher resistance.
The additional resistance gives a stronger push to support the weight of the insects.
These observations were made by John Maynard Smith and M.J. Davies in the 1950s.
This was done through an experiment where they etherized a few hoverflies and pasted them on a pin.
Later they surrounded them with metaldehyde particles and conducted flash photography to record the length of exposure.
The resulting pictures were quite underwhelming according to modern standards but strong enough to record the above observations.
Frequently Asked Questions
What are hoverflies attracted to?
Hoverflies are attracted to any area that has an abundance of flowering plants.
They hover around these flowers to mate and consume pollens and nectar.
Also, in the initial life stages as larvae, they love to be around aphid populations as they are the primary food source.
You can attract them to your garden by having bright-colored flowers nearby.
Why do Hoverflies hover around you?
Hoverflies are especially attracted to the salts present in human sweat.
If you are drenched in sweat, hoverflies will hover around you to lick and consume the sweat beads.
To avoid this, use sweat repellents that will keep you dry on hot sunny afternoons.
What is the purpose of a hoverfly?
In an earlier stage of the life cycle as larvae, these insects consume aphids, scale insects, and more to attain enough nutrition to transition into the pupal stage.
Once they grow up, they fall and hover around flowers to consume nectar and pollens and to find mates.
Where do hoverflies go at night?
Various species of flies and insects are usually attracted to bright lights at night. Once they spot a light source, they start flying toward it.
Also, some insects search for a safe spot to rest after the sun goes down. You can find them on twigs, branches, and on the undersides of leaves at night.
Technically insects like bees and hoverflies should not be able to fly.
The experiments conducted by John Maynard Smith and M.J. Davies in the 1950s explained how these insects could fly despite the laws of physics being stacked against them.
We hope the article helped you get some insight into the amazing capability of flight that these insects possess.
Thank you for reading!
Why hover flies hover is the subject of several emails that we have received over the years. While some were letters of wonder, others were all about disgust and fear.
Read on to find out more about the interactions of these insects with human beings and the varied reactions people have to their flying abilities!
Letter 1 – Corn-Tossel Fly? might be a Flower Fly
When I was a young lad I would often go fishing with my grandfather and in the hot days of summer we would often encounter "corn-tossel flies." In all actuality I have no idea what they are called, but I see them quite often and I have always been curious about them. I do not have any photos of them but I think I could describe them to you and you would be able to place them rather easily seeing as how they are a fairly common bug (in southern Illinois anyway).
The bug is obviously a fly of some sort that has an elongated and flattened body that is striped like a bee (yellow and black) and it has a head like a house fly (two large red eyes being the majority of its head). One thing I find to be very amusing is its behavior. The fly seems to hover much like a hummingbird, whereas your average fly would just zoom on by and land at its desired location, the "corn-tossel fly" (as my grandpa coined it) would hover over a certain location before deciding to land almost as if it were checking out the area to see if it would be ok to land on. Another amusing behavior it possesses is its way of landing on hand, arm, or leg and doing "the fly suck". Whilst doing "the fly suck" it will move about the immediate vicinity of where it decides to land and bob its little bee-butt up and down with every other step. When I first discovered these peculiar flies the motion of its butt reminded me of how a bee stings, and I used to think that it was in the process of stinging when this occurred.
If you could identify this bug and provide me with a little info on it I would greatly appreciate it!
Dear CTF Guy,
We have never heard of a Corn Tossel Fly. It sounds like you are describing a Flower Fly, Family Syrphidae. The larvae eat aphids and other destructive plant pests. The adults eat pollen, which is why perhaps they are attracted to corn tassels. The only photo we have was sent by Daniel from Mexico City.
Letter 2 – 2 Alaskan Hover Flies
Yellow Jacket Hover Fly Here are some more pictures from Eagle River, Alaska. These are a hover fly that is an excellent yellow jacket mimic. Their front legs are black and they usually hold them out in front and wave them about like yellow jacket antennae. The other four legs are yellow like a yellow jacket. In these pictures, it is hard to see the front legs, as he is using them to eat. These are very hard to distinguish from the local yellow jackets. The only reason they are easy to spot this year is there are no yellow jackets near my house. We had a late, cold spring, followed by a hot dry summer, and all the yellow jackets and hornets seem to have died off. Last year, there were so many that my yard had a constant loud hum from the thousands of yellow jackets. Anyway, all the yellow jacket mimics really stand out this year (like the wasp moth I sent last month). Also, here is another hover fly. The color morphology was different from the others I have seen on your site, so I thought you would like to add them to your collection. Finally, here are two beetles on a wild prickly rose. I’m not really looking for an ID, I just thought it was a neat picture and figured you’d like it. (sorry about the black specks, the image sensor was dirty and I was using a very small aperture). I’m sure you are swamped with bug pictures right now, but would you be interested in a CD of some of the better ones from this summer? I could send you one this winter after things slow down a bit. -David ps. If anyone is interested, the camera used was a Canon EOS 5D with a EF – 100mm f/2.8 USM Macro lens and MT-24 Macro Flash Hi David, Yes, we really are swamped right now, but there seems to never be a slow time. Winter in US means summer in Australia, and we get many requests from Down Under. WE feel guilty when we do not respond to your letters, but we have a better request than you sending us a CD. A CD would not have an explanatory letter and we like having information. Please limit your submissions to one insect, or type of insect, per letter. It makes it so difficult to get your letters with four or five wonderful images that need to be posted on numerous pages so we procrastinate, then forget. Off the tops of our heads, we cannot even recall the Wasp Moth you mention in this letter. Did we post it? If not, please resend with information. Meanwhile, we are happy to post your unidentified Alaskan Hover Flies. The Yellow Jacket mimic might be the genus Chrysotoxum.
Letter 3 – Australian Hover Flies Mating in Flight
Hoverflys mating in flight Sun, Feb 22, 2009 at 9:43 PM Hi guys, Just spotted a hoverfly in the garden that was staying very much in the one spot so grabbed the camera and turned out to be this pair in mating flight.. Sorry the top guy is not real sharp around the head, ID is Common Hover Fly – Ischiodon scutellaris. Thought you might like them for the buglove pages aussietrev Queensland, Australia Hi Trevor, What an amazing and romantic photograph. Thanks for providing our readership with a species identification as well.
Letter 4 – Unknown Hover Fly from New Zealand might be Three LIned Hoverfly
What is this? December 25, 2009 We have never seen a bug like thin in NZ before. Any idea what it might be? It looks like a cross between a blow fly and a wasp. Any light you could share on it would be great. Thanks heaps Paulo the wonderer Auckland New Zealand Dear Paulo, The ventral view of your photograph is not ideal for identification purposes, and a dorsal view is much preferred. We believe this is some species of Hover Fly in the family Syrphidae. You might try comparing the images on the Insects of Brisbane Syrphidae page to see if any look close to your specimen.
Letter 5 – Flower Fly, we believe, from Kuwait
bee or fly March 8, 2010 Hello, I am writing to you from an American military base in Kuwait. I am in pest management and would like to calm the fears of my fellow military members. Recently we have had a large number of flying insects that appear to be bees but i believe they are flies. They have been hanging out on shaded walls to stay out of the heat. They do not behave like bees they only look similar to bees. They range in size from 1/4″ to 1/2″. Leslie B Kuwait Hi Leslie, We mean no disrespect in writing this, but we believe that there are far greater threats to our brave military men and women in Kuwait than either bees or flies, and we hope that there is a strong support system for calming their fears regarding bombs, missiles and bullets. This is a fly, and we believe it is a harmless Hover Fly or Flower Fly in the family Syrphidae, a group that has numerous members that mimic stinging insects. For the record, in the scheme of things worldwide, Flies would generally be a cause of greater concern than bees whose stings are temporarily painful, but cause no lasting harm except in the case of severe allergies. On the other hand, Flies, which include Mosquitoes, often bite and they can be serious disease vectors, especially in warmer climates. Malaria, yellow fever, dengue fever and sleeping sickness are all spread by the bites of mosquitoes and flies, and diseases like typhoid fever, anthrax, leprosy, cholera, conjunctivitis, tuberculosis, dysentery and diarrhea can be spread through contact with the Common House Fly. Your Flower Fly, we are pleased to report, is benign and no cause for alarm. Daniel, Thank you so much for your quick response and your honest words. Thankfully not many bombs, missiles, or bullets flying in Kuwait but yes we have support and preparation to face the human threat if it presents itself. It is odd but true that some fear the insects so fiercely. After spending some time researching on your website I was able to form an educated guess that it was from the Syrphidae family, and indeed mimicking a bee. I appreciate your email confirming my suspicions. I appreciate you stressing the medical importance of the fly as I have spent the majority of my time over the last 3 months battling the common fly and hope the upcoming 100 degree plus weather will greatly assist me in the matter of controlling the pest. I may be the only one on base praying for higher temperatures. Thank you again for your assistance and no disrespect was taken.
Letter 6 – Flower Fly: Eristalinus taeniops
Bee/Fly with Yellow Striped Eyes? March 30, 2010 Saw this on the patio a couple days ago. Thought it was a bee at first, but the yellow striped eyes were pronounced. It’s about the size of a common bee or fly. Do you have any idea what this might be or what would cause the markings on the eyes? Kyle B. Long Beach, California Dear Kyle, Though it resembles a bee, your fly is not a Bee Fly. It is a Hover Fly or Flower Fly in the family Syrphidae. The species Eristalinus taeniops, is only reported from California on BugGuide.
Letter 7 – Common Hover Fly from Australia
Flying nectar loving bugs Location: Sydney, Australia October 14, 2010 5:58 pm Two that I photographed yesterday around a flowering bush in Sydney, Australia. None of my friends can identify either of them and so far I’ve been unable to identify them on-line. Signature: Mike Gordon Hi Mike, For classification purposes in our own confusing archives, we like to have each species of insect identified on its own posting. The first image you have submitted to us we quickly identified on the Brisbane Insect website as the Common Hover Fly, Melangyna viridiceps, though in the photograph posted there, the wings are covering the abdomen of the insect and the markings are not as apparent. We followed the link provided to the Csiro website, and the photo provided there indicates a much more obvious match.
Letter 8 – Hover Fly
Interesting Bee Location: Jaffery, NH, White Arrow Trail, Mt. Monadnock July 4, 2011 10:50 pm My cousin and I were walking down an access road from the main path (White Arrow Path) at Mt Monadnock, in Jaffery NH, When we spotted a bee, just hovering there. We walked past the bee, and it did not move, using quite a bit of energy to stand in one spot constantly. So we walked on, and there was another one, facing the SAME direction and hovering, this time I approached it and it moved in a triangle pattern and went back to the same spot, exactly the same spot, only this time its abdomen throbbed and a stinger emerged. At that point we moved on. Then we saw a third, then fourth… I took a photo by the 7th one, they were in 20 or so foot intervals all the way down the path, all facing the same direction and very determined to stay in their one by one inch spot at a specific height, very calculated seeming spot in the air. What kind of bee is this and what could it possibly be up to staying in one spot for this long, and this specific to that ONE one inch cube of airspace??? Signature: -Vaughn Saball Hi Vaughn, This is not a bee, but rather it is a Hover Fly in the family Syrphidae. Many Hover Flies mimic bees for protection. The behavior you described is very interesting. We hope we are able to research a species name for you. Alas, the photo you provided is an excellent action photo, but it doesn’t provide us with a view of the markings which may make species identification quite difficult. Meanwhile, you can read some general information on Hover Flies on BugGuide. We did locate this scholarly article published by the Cambridge Entomological Club in 1929 entitled Notes on the Syrphidae Collected at Jaffrey and Mount Monadnock, N.H., with a Description of a New Species by C. W. Johnson.
Letter 9 – Flower Fly, we believe
Subject: Large bee in North bay northern Ontario. Location: Calendor northern Ontario September 28, 2014 4:31 am We noticed lots of bees on this particular fall day. Cannot seem to find any similar to identify. Signature: Carol S Amour Dear Carol, This is not a bee. If you inspect the image closely, you will see only one pair of wings, indicating that this is a fly, albeit one that mimics bees. We believe your fly is in the family Syrphidae, the Hover Flies and Flower Flies, and many members in the family mimic bees and wasps as a means of protection. Though we have not had any luck locating an exact match, we believe your individual most closely resembles the members of the subgenus Eoseristalis that are pictured on BugGuide.
Letter 10 – Hover Fly
Subject: What is this bee? Location: Sub alpine region of Colorado July 23, 2017 6:56 am Hey bugman! I snapped this photo of a tiny bee about to land on a flower for nectar. I am in Boulder County, CO and this shot was taken at or above 10,000ft. It was mostly black and when it wasn’t zipping around, it would hover. I’m stumped! Signature: He with the Bee This is not a Bee. This is a Hover Fly or Flower Fly in the family Syrphidae. Many harmless members of the family Syrphidae are effective mimics of stinging bees and wasps.
Letter 11 – Ambush Bug eats Flower Fly
Subject: Found on Asters and it appears to prey on bees Geographic location of the bug: Bloomington, Indiana Date: 10/16/2017 Time: 09:31 PM EDT I’ve seen a couple of these bugs. They are pretty small, only looking like a tiny piece of bark that fell onto the flower. They seem to park themselves on the aster and aren’t afraid of being photographed. Today, I got a shot of one sucking on the abdomen of a small bee. It looked like the bee wad dead. How you want your letter signed: Teddy Alfrey Dear Teddy, Your images are exquisite. The predator in your images is an Ambush Bug, and though it resembles a bee, the prey is actually a Flower Fly or Hover Fly in the family Syrphidae. Ambush Bugs are frequently found on blossoms where they ambush insects, many of which are pollinators. Daniel, Thanks for the “exquisite” comment, and the quick reply!! My thought was that the prey was something like a Mason Bee, but of course, you’re right about the Flower Fly. I have quite a few insect photos on my Flickr page: https://www.flickr.com/photos/
Letter 12 – Hover Fly from Hawaii
Subject: Some kind of hoverfly? Geographic location of the bug: Pu’u Wa’awa’a, Big Island, Hawaii Date: 01/25/2018 Time: 06:32 PM EDT Your letter to the bugman: Greetings, I saw this fly on a mamane flower at around 4,000 feet, near the top of Pu’u Wa’awa’a. It looks like some kind of hoverfly. I thought the markings on the back end would make it easy to ID, but I can’t find one that looks exactly like this. Any ideas would be appreciated. Mahalo. How you want your letter signed: Graham Dear Graham, This is indeed a Hover Fly or Flower Fly in the family Syrphidae, a group whose members often impersonate stinging Bees and Wasps as protective mimicry. Many members of the family closely resemble one another, so exact species identification can be difficult, and this is further exacerbated in Hawaii where many insects and other creatures are not native. This FlickR image of Allograpta obliqua looks very similar, and according to BugGuide data, it is a very far ranging species across North America, making it a likely candidate for its also living in Hawaii. According to Phorid.net: “This species is found from North America to Southern South America, and has been introduced in Hawaii. A few specimens were collected at both our Year 1 Malaise trap sites. The larvae feed on aphids, and were found to be a major component of the syrphid fauna of organic lettuce fields on the Central Coast of California.” Hi Daniel, Many thanks for the identification. That certainly looks like what I saw. Armed with that information, I found several other sites (scholarspace.manoa.hawaii.