March Fly: All You Need to Know for a Bite-Free Summer

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March flies, belonging to the family Bibionidae, are fascinating insects that are commonly found buzzing around during springtime. They are typically dark gray in color, but some species may display bright spots, adding a touch of vibrancy to their appearance. Often confused with midges, these flies tend to thrive in damp environments, making wetlands a popular habitat for them.

The life cycle of March flies involves a larval stage, where the maggots grow to be ¼ to 1 inch long and are usually gray in color. These peculiar larvae possess projections at their rear, which aid in their identification. As they mature and turn into pupae, they appear slender and brownish, finally emerging as adult flies that have distinguishable features between males and females; for instance, female March flies have smaller eyes compared to their male counterparts.

Along with their unique appearance and life cycle, it’s important to understand the role of these creatures in the ecosystem. March flies act as decomposers and help break down organic matter. Furthermore, they serve as a food source for numerous predators, including birds and other insects, thereby contributing to the intricate balance of nature.

March Fly Basics

Identification and Characteristics

March flies, belonging to the family Bibionidae, are small, flying insects with distinctive features. To help identify them, consider these characteristics:

  • Dark gray bodies, sometimes with bright spots of color
  • Antennae with multiple segments
  • Some species have large eyes, especially in males
  • Smaller eyes in females

An example of a March fly species would be the Bibio slossonae found in some parts of North America.

Diversity of Species

Within the March fly family, there are several species. Some species of March flies have a connection to marsupial species in Australia, which can be a unique aspect within the insect world. The diversity of species can be observed in their various habitats and distribution.

Habitats and Distribution

March flies occupy different habitats and geographical locations, including:

  • Wetlands and damp areas
  • Found in both North America and Australia
  • Strong connection to marsupial species in Australia

To sum it up, March flies are an intriguing group of insects with distinct characteristics, diverse species, and widespread distribution that can be observed in various habitats.

Life Cycle and Breeding

Eggs and Hatching

March flies, like many insects, begin their life cycle as eggs. Female march flies lay their eggs in damp soil or decaying leaves. Upon hatching, tiny larvae emerge and start feeding on organic matter.

Larval Stage

During the larval stage, march fly maggots are:

  • Gray in color
  • 1/4 to 1 inch long
  • Found in damp environments
  • Equipped with projections at their rear

These maggots consume decaying plant material and fungal growths on the soil surface, making the most of their larval resources.


Once the maggots grow and reach a certain size, they undergo pupation. Pupae are:

  • Slender
  • Brownish in color

This stage serves as a transition period from larval to adult stages.

Adult Stage

Upon emerging from the pupae, march flies enter the adult stage. Some characteristics of adult march flies include:

  • Dark gray bodies, with some species having bright color spots
  • Bodies with small bumps and protrusions
  • Females having smaller eyes compared to males

The adult march flies play an essential role in pollination, as they feed on nectar from flowers.

Here’s a comparison table for the different stages in the life cycle of march flies:

Life Stage Appearance Habitat Role
Eggs Tiny Damp soil or decaying leaves Begin life cycle
Larvae Gray, 1/4 to 1 inch long Damp environments Feed on organic matter
Pupae Slender, brownish In soil Transition from larvae to adult
Adult Dark gray, small bumps, sexual dimorphism in eyes Various environments Pollination, reproduction

Diet, Predators and Impact

Feeding Habits of March Flies

March Flies, belonging to the family Bibionidae, exhibit diverse feeding habits. Adult flies primarily feed on nectar from flowers, making them pollinators in the process. Some species are attracted to blood, seeking out hosts like livestock and humans for sustenance.

The larvae of March Flies, also known as predatory maggots, consume decaying organic matter and various invertebrates. This helps in controlling populations of potential pathogens and maintaining the balance in the ecosystem.

Predators and Threats

March Flies face numerous threats and predators in their natural habitat. Some of their predators include:

  • Birds
  • Spiders
  • Predatory insects and their larvae, such as lacewings and ladybugs
  • Frogs

In addition to these natural predators, human activities also endanger March Flies. Habitat destruction and the widespread use of insecticides can have a severe impact on their populations.

Environmental Impact

Due to their feeding habits and role as pollinators, March Flies are crucial in maintaining the health and balance of the ecosystems they inhabit. As pollinators, they aid in the reproduction of plant species, ensuring the survival and propagation of various flora. Their larvae, by consuming decaying organic matter, serve as natural waste processors and help in nutrient recycling.

Here’s a comparison table of March Flies’ traits:

Trait Benefit/Role
Feeding on nectar Pollination and plant propagation
Feeding on blood Host-seeking behavior and survival
Larval feeding habits Organic waste processing and nutrient recycling
Attraction to polarized light Increased navigation efficiency for certain species

In conclusion, understanding the diet, predators, and impacts of March Flies helps highlight their significance to the environment and the ecosystems they inhabit.

March Fly Bites and Health Concerns

Bite Mechanism

March flies have piercing mouthparts that they use to bite and draw blood meals from their hosts. Their bite is typically sharp and sometimes painful.

Allergic Reactions and Risks

Some people may experience allergic reactions to March fly bites, which may include:

  • Itching
  • Redness
  • Swelling

It is essential to remember that these reactions may vary from mild to severe and may require medical attention in extreme cases.

Blood Loss and Livestock Health

March flies are not only a concern for humans but also for livestock. Blood loss due to multiple bites may lead to health issues in livestock, especially if the bites lead to infection.

Prevention and Control

Insect Repellents

When dealing with March flies, the use of insect repellents is recommended for their effective protection. Two main ingredients that are commonly used in repellents:

  • DEET – This is one of the most popular and widely used active ingredients in insect repellents. It is highly effective in repelling a variety of insects, including March flies.
  • Picaridin – A newer alternative to DEET. It is equally effective in repelling insects, with the added benefit of not causing damage to some materials like plastics.

Example: For protection against March flies, consider using a DEET-based repellent or a Picaridin-based repellent.

Comparing DEET and Picaridin

Feature DEET Picaridin
Efficacy High High
Material Compatibility Lower Higher
Skin Irritation Some cases Less likely

Clothing and Protective Measures

To fend off March flies, use practical clothing and protective measures:

  • Wear long sleeves and long pants to cover the arms and legs.
  • Opt for light-colored clothing, as dark colors may attract March flies.
  • Avoid using fragrant personal care products, such as perfumes and scented lotions, that might entice insects.

Mechanical Traps and Pesticides

March flies can also be controlled by employing mechanical traps and pesticides:

  • Use fly traps designed specifically for March flies. These traps provide a safe and non-toxic method to control the insects.
  • If necessary, apply approved pesticides in the affected areas. Be cautious, follow the instructions, and consider potential risks, especially for children and pets.

Note: Traps and pesticides should be used in conjunction with other prevention methods. Always prioritize safety and be environmentally conscious when using chemicals.

March Flies in Popular Culture

Role in Fishing

March flies play a role in fly fishing, as their nymph and adult stages are used as models for artificial flies. Some popular fly patterns resembling March flies include:

  • Dun
  • Dry fly
  • Elk hair caddis

These patterns mimic March flies in their various life stages, aiming for a natural presentation to attract fish.


  • Imitates a natural food source for fish
  • Can be useful in various fishing situations


  • May not be as effective as other fly patterns

Lovebugs and Their Significance

March flies belong to the family Bibionidae, and a unique member of this family is the lovebug. These insects are often seen in pairs, joined together even while flying. Their behavior has led to the name “lovebug,” symbolizing unity and love in some philosophy contexts.

Notable Lovebug Features:

  • Distinctive black and red coloring
  • Mating pairs remain joined
  • Swarm in large numbers

Lovebugs are harmless to humans, having no biting or stinging ability. However, their swarming behavior can cause minor problems, such as reduced visibility for drivers or clogging automotive radiators.

Comparison Table

Property March Flies Lovebugs
Family Bibionidae Bibionidae
Significance Fishing Symbolism
Life stages Egg, Larva, Pupa, Adult Egg, Larva, Pupa, Adult
Known for Fly patterns Mating pairs

Reader Emails

Over the years, our website, 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 – March Fly from UK


Subject:  Large Fly?
Geographic location of the bug:  Darlington, County Durham
Date: 07/30/2019
Time: 07:30 AM EDT
Your letter to the bugman:  Hello there. Can you please help me identify this fly?
I found it in the kitchen after a party and it appeared to be sucking the surface of the cake lid.
I lifted it outside and it is still there this morning.
Is it friend or foe? I’d like to help it if needs be.
How you want your letter signed:  Victoria

March Fly

Dear Victoria,
This is a female March Fly in the family Bibionidae, a group sometimes called St. Mark’s Flies in the UK, though that common name might refer to only a single species in the genus Bibio.  Based on images posted to NatureSpot, your individual might be
Bibio johannis, or possibly Bibio pomonae, the Heather Fly.

March Fly

Letter 2 – St. Mark's Fly from U.K.: Heather Fly


A scary looking fly, what is it??
August 20, 2009
I was camping in the uk last week and noticed a few of these strange looking flies, I thought nothing more of it until I have noticed very nasty bites on my ankles and my head, I was wondering if you could identify it for me, and tell me if i need to worry!
Karl Chapman
Derbyshire, UK

St. Mark's Fly
Heather Fly

Hi Karl,
We hesitate to tell you not to worry, but you need not worry about this insect.  We believe this is a March Fly in the family Bibionidae.  We are going to leave actual species identification to a Dipterist, but we found several UK species with similar looking photos.  There is a Fever Fly, Dilophus femoratus, that is shown in close-up on the Bio-Images Virtual Field Guide (UK) page that looks close.  A closer match would be Biblio johannes, called a St. Mark’s Fly, on the same Bio-Images website.  Though the color doesn’t match, the spine at the joint of the foreleg matches another St. Mark’s Fly, Biblio marci, also pictured on the Bio-Images website. The Nature Observer’s Scrapbook page has this to say about St. Mark’s Flies:  “St Mark’s fly owes it’s common name to its annual habit of appearing around St Mark’s day, 25th April.
It seems odd to me that an insect as substantial as this should be deemed to be a ‘midge’. This is the largest of the 18 strong Bibionidae family of black day flying midges. The females are about 13mm in length and the males about 10mm.
It is slow and cumbersome in flight with its legs dangling clumsily – and that is while it is on it’s own. When they are mating, it is not unusual to find them in even more unwieldly flight, still coupled together with the larger female dragging the hapless male to the next resting place.
The differences between male and female can clearly be seen in the upper image. The female is significantly larger but has a much smaller head with smaller eyes set on either side of the head. The male on the other hand has large eyes touching each other.
The single, strong, forward pointing spine on the outside of the tibia of the front legs (highlighted in the lower image) is an identifying feature of the Bibio family, helping to distinguish it from the similar Dilophus family – to which the fever-fly (see below) belongs.
The conformation of the wings is such that when folded, one wing completely overlays the other.
It breeds underground and the larvae feed largely on decaying vegetation but are also blamed for damage to crop roots.
One ‘oddity’ of Bibio species is that the larval structure appears to be more primitive than the adult fly conformation would lead one to expect, indicating some evolutionary aberration in their development.”  Based on the head, this fly is a female since males have much larger eyes.

St. Mark's Fly
Heather Fly

Clarification from Karl
Hi Karl:
There are apparently 13 species of ‘March Flies’ in the genus Bibio listed for Great Britain. From what I can tell the closest match to yours is B. pomonae; the Heather Fly. It was the only one I could find with red colouring on the legs that doesn’t extend beyond the femur. The peak of the flying season in GB is July-August so the timing would be right. The species is very widely distributed in Europe, Iceland to Russia and down to the Mediterranean. According to some references it prefers higher elevations, hence the common name; others give hedgerows as the preferred habitat. The larvae feed on roots and the adults eat nectar, so I suppose your bites remain a mystery. For reference you could check out or Nice photos bye the way. Regards. K

Letter 3 – Mating March Flies


Subject: flying bug
Location: Boston, MA
May 9, 2016 10:18 am
Help, see the attached photo. These flying insects seem to have appeared after I just moved 20 yards of straight compost into my back yard. They are there all day swarming around not sure about at night. They appear to be mating. TThey have not gone away and now its been close to 2 weeks. Anyway to remove them or at least limit the amount of them!
Signature: DaveLaf

Mating March Flies
Mating March Flies

Dear DaveLaf,
These are mating March Flies in the family Bibionidae, and probably in the genus
Bibio that is represented on BugGuide.  The male is the one with the larger head.  We do not provide extermination advice.

Letter 4 – Mating Minute Black Scavenger Flies


Subject: Flies that love “docking”
Location: Santa Barbara, CA
April 6, 2016 4:54 pm
In the past two weeks or so (since mid-February), my apartment in Santa Barbara, CA has become home to these little flies (~3mm long) that seem to like to spend all their time docked posterior-posterior. Solo, they’re pretty active and prefer windows, mirrors, or just flying around roughly at head height; docked, they like walls and (especially) ceilings, and seem to spend 8–10 hours totally stationary—though when they do move, they do so as one, rather than separating first. They must go somewhere to hide overnight, because I only see them during the day. Also, unlike the fruit flies that sometimes invade my apartment, I’ve never figured out what these eat.
I’ve just never seen anything quite like this—in fact, for the first week or so, I thought it was a single long, skinny insect, and was very surprised the first time I saw that it was actually a pair. Maybe you can shed some light on what these are?
Signature: Curious in California

Probably Mating March Flies
Mating Minute Black Scavenger Flies

Dear Curious in California,
We believe these Dipterans are mating March Flies, but we really wish your image had higher resolution allowing us to see the details better.  March Flies in the family Bibionidae are sexually dimorphic, meaning there is a distinct visual difference between the sexes.  Males have much bigger heads and eyes than females, and the head in the upper Fly in your image is difficult to discern.  According to BugGuide, the species is found in Santa Barbara and BugGuide has an excellent image of a mating pair.  Of the family BugGuide notes:  “Adults emerge synchronously in huge numbers and often form dense mating aggregations. Males form loose ‘swarms’ and copulate immediately with females as they emerge from the soil. After mating, female bibionines dig a small chamber in the soil with their fossorial fore tibiae, lay eggs, and die within the chamber (
Plecia lay eggs on the soil surface). Adults are short-lived (3-7 days).”  Perhaps the most notoriously famous March Flies are the Love Bugs in the genus Plecia from the southeast, including Florida, that emerge by the millions and seem to be perpetually in flagrante delecto.  While we were much amused at your “docking” euphemism, since the insects in your image represent opposite sexes, the term is really not accurate.  A much better visual representation can be found in these mating Big Poplar Sphinxes.

Possibly March Fly
Minute Black Scavenger Fly

Thank you for the reply! I had in fact wondered whether they were love bugs (since I was able to guess what they were really up to), but the pictures I found online looked different enough to what I was seeing—and the stated range on Bibionidae also being larger than the 2–3mm of my “guests”—that I wasn’t sure. Unfortunately, the only camera I have access to is the one on my outdated iPhone, so those pictures are probably as high-resolution as I can get. In person, even under low magnification, I can’t quite tell whether their heads (which are both under 0.5mm) are different sizes. However, on the basis of descriptions like “The male and female attach themselves at the rear of the abdomen and remain that way at all times, even in flight” (from Wikipedia), which comports exactly with what I’m seeing, I’m satisfied that these are in fact Bibionidae. So, thank you again for resolving the mystery.

Update:  April 9, 2016
Thanks to a comment from Cesar Crash, we agree that these are mating Minute Black Scavanger Flies in the family Scatopsidae, which is represented on BugGuide where it states:  “Larvae feed on decaying organic matter, such as detritus or excrement.”  Minute Black Scavenger Flies and March Flies are classified together in the infraorder Bibionomorpha.

Letter 5 – Mating March Flies


Higher evolution?
Sun, May 31, 2009 at 1:57 PM
Hi Lisa Anne and Daniel, twice I have found mating March Flies (?) with the head of one being miniscule in comparasion to the other. Could they be as their human counterparts in that the male’s thinking has been usurped by another body part? Perhaps this then is our future.
Just curious,
near Casper, WY

March Flies (male on left) Mating
March Flies (male on left) Mating

Hi again Dwaine,
While your evolutionary comment is highly amusing, the flaw in the logic is that the male March Fly has the larger eyes, and larger head.  We are not certain what species your March Flies in the family Bibionidae represent.  Lovebugs in the genus Plecia are a group of March Flies with considerable notoriety.

Letter 6 – March Fly, NOT Stiletto Fly


Subject:  unknown insect
Geographic location of the bug:  Lynnwood
Date: 04/06/2018
Time: 01:12 PM EDT
Your letter to the bugman:  I found several of these insects on the emerging leaves of a red currant.  Can you tell me what they are and whether they are innocuous or harmful?
How you want your letter signed:  Nancy Wyatt

March Fly

Dear Nancy,
We believe this is a Stiletto Fly in the family Therevidae, and according to BugGuide:  “Adults are nectar feeders; larvae prey on soil arthropods.”  Several species are pictured on Natural History of Orange County, but none looks exactly like your individual.  ResearchGate has some images of Australian Stiletto Flies that look similar to your individual.  We hope to get a second opinion on our identification.

Wow, that was fast!  I’m sure you’re right about the identification.
I do so much appreciate your interest and expertise.  And I gained more knowledge about my insect neighbors.
The fly larvae can eat all the soil arthropods they like from my garden!

Eric Eaton provides a correction:  March Fly
Sorry, I am “out of the office,” hence the delay in replying.  This is a dance fly, probably genus Empis.  Probably female, too.  Pretty common early spring flies in the Pacific coast states.
author, Kaufman Field Guide to Insects of North America

Ed. Note:  Once Eric Eaton provided us with a genus name, we did find this individual from Ireland posted to Alamy and this individual from California posted to BugGuide.

Well, that sounds a lot more peaceful than “stiletto fly”.  I either case I don’t have to worry about the larvae eating my currant plants.  It’s a real struggle saving them from the aphids in the spring. I’m so impressed that you and your colleagues would provide this service, which I have bookmarked and will recommend to all my friends in the gardening community here.

Letter 7 – March Fly we believe


Subject: Orange Belly Fly/mosquito
Location: Mississippi, United States
September 7, 2013 10:26 am
Can you please tell me what these are? They are the most annoying insects more annoying than flies or mosquitos!
Signature: ThomasOwens

Probably Lovebug
Probably Lovebug

Dear Thomas,
We wish you had a dorsal view of this insect, which we believe is a March Fly in the genus
Plecia, commonly called a Lovebug because mated pairs remain joined for an extended period of time.  They can get very common in the south when they form huge swarms.  According to BugGuide, they are also known as Honeymoon Flies.

Probably March Fly
Probably March Fly

Hi Thomas,
Thanks for sending a dorsal view.  We no longer believe this is a Lovebug, but we still believe it is some species of March Fly.

Letter 8 – March Fly


Subject:  Possible ant with very short antenna
Geographic location of the bug:  North Texas (DFW)
Date: 03/25/2018
Time: 09:12 AM EDT
Your letter to the bugman:  Hi,
I found this bug on my patio. At first I thought it was an ant, but its antenna seem too short. It doesn’t really look like pictures of termites that I’ve seen. It seems too small to be a wasp.  I would really appreciate it if you could give me some guidance as to what it might be! Thank you!
How you want your letter signed:  Alyssa

March Fly

Dear Alyssa,
This is a March Fly in the family Bibionidae, not an Ant.  March Flies often appear suddenly in large swarms, they remain a few days and then they are gone.  Your individual appears to be a big eyed male.  There is a species of March Fly that appears in such large numbers of mating pairs in Florida that they are called Love Bugs.  Because of the red legs, we believe this might be Bibio femoratus which is described on BugGuide as “Shining black, dense yellow hair, red femora” and it is found in “Most of North America, except Canadian arctic and Western USA.”  BugGuide data includes reported sightings Oklahoma, but not Texas, but that just means there have been no reports to BugGuide from Texas.

Letter 9 – March Fly


Subject:  Flying insect, about1/4”
Geographic location of the bug:  High desert Reno NV among the sagebrush
Date: 05/11/2019
Time: 05:19 PM EDT
Your letter to the bugman:  Tons of them flying around in my empty lot
How you want your letter signed:  Nn2036

Male March Fly

Dear Nn2036
This is a March Fly in the family Bibionidae, and the large head and large eyes indicate it is a male.  Inspect them more closely and you should find small headed females as well as mating pairs.  Based on BugGuide images, we believe this March Fly is
Bibio albipennis because of its clear wings.

Letter 10 – March Fly from Canada


Subject:  Black-orange bug
Geographic location of the bug:  New Brunswick, Canada
Date: 06/03/2019
Time: 10:27 AM EDT
Your letter to the bugman:  Hello,
On May 31st 2019 I have found a large number of these strange bugs appearing here in New Brunswick, Canada and also in Maine, USA. They do not seem to harm anything. I have seen them in clusters of over 1,000. They are fly like and have orange and black segmented legs. Wings have markings. The antennae are very short, maybe around 2mm. I have looked all over the internet at thousands of bugs and can not find anything anywhere. Any help would be appreciated.
How you want your letter signed:  JP

March Fly

Dear JP,
This is a March Fly in the family Bibionidae, and during mating season, there may be great numbers of adults emerging and mating, and then vanishing as quickly as they appeared.  We believe your individual might be a female
Bibio xanthopus, and you can see an image of a sexually dimorphic male which has much larger eyes pictured on BugGuide.

Letter 11 – March Fly in Alaska


Subject:  Dozens of these guys all of a sudden.
Geographic location of the bug:  Eagle River, Alaska
Date: 09/08/2021
Time: 01:11 PM EDT
Your letter to the bugman:  A couple days ago I noticed dozens of these guys all over my deck, cars, and front of house. Not sure where they came from or what they are. Any ideas would be greatly appreciated. Thanks in advance.
How you want your letter signed:  Bryan

March Fly

Dear Bryan,
This is a March Fly in the family Bibionidae and probably the genus
Bibio.  They often appear in great numbers and then just as suddenly they will be gone.  According to BugGuide:  “Adults emerge synchronously in huge numbers and often form dense mating aggregations. Males form loose “swarms” and copulate immediately with females as they emerge from the soil. After mating, female bibionines dig a small chamber in the soil with their fossorial fore tibiae, lay eggs, and die within the chamber (Plecia lay eggs on the soil surface). Adults are short-lived (3-7 days).”

Thanks for the quick info and links. Now at least I know what I’m dealing with. Hopefully they disappear again soon.
All the best,

Letter 12 – Mating March Flies


What is this bug? Please
Hello, Could you please tell me what these are? I live in California on the Central Coast and found these in my backyard. I have never seen these in my area and would like to know if they are harmful as they were mating. Thank You

Hi Maryann,
These are mating March Flies in the family Bibionidae. You can find more information on BugGuide which states: “Larvae feed on decaying organic matter, such as feces, roots, logs”, so they are actually beneficial. Some species, notably Love Bugs in Florida and the Southeast, can get very numerous at times and become a nuisance. The male has the bigger eyes and corresponding bigger head.

Letter 13 – Mating March Flies


Subject: Unidentified bugs
Location: Catskill, NY
September 28, 2015 3:26 am
On Sept 27, 2015, I photographed these two enjoying the after sun on my car door in Catskill, NY. They seemed to be enjoying themselves and so was I! Love to know what they are.
Signature: Ken Tannenbaum

Mating March Flies
Mating March Flies

Dear Ken,
These are mating March Flies in the family Bibionidae, and they exhibit sexual dimorphism in that the head of the male is larger to accommodate the larger eyes.  We believe we have correctly identified your March Flies as
Penthetria heteroptera thanks to images posted to BugGuide where it indicates they are active in the fall, distinguishing them from most March Flies that appear in the spring.

Letter 14 – Mating March Flies


Subject: Is this a type of fly?
Location: Lexington, MA
May 26, 2016 5:22 am
I live in Eastern Massachusetts and noticed these flying insects swarming all over our backyard. They don’t seem to bother humans but they really seem to like the grass seed on our overgrown grass. Can you please tell me what they are?
Signature: Gordon

March Flies
March Flies

Dear Gordon,
These are mating, sexually dimorphic March Flies in the family Bibionidae.  Males March Flies can be distinguished from females by their larger heads and bigger eyes.  We suspect because of your location they are most likely 
Bibio albipennis based on BugGuide information.

Letter 15 – Mating March Flies in New Zealand


pair through window
November 26, 2009
A pair of bugs, about 1 cm head to tail each, photographed through a window. mating? southern hemisphere spring (november 26).
Christchurch, New Zealand (43 S)

Mating March Flies in New Zealand
Mating March Flies in New Zealand

Hi Greg,
These are March Flies in the family Bibionidae.  There is a North American species found in Florida and vicinity that are known as Lovebugs because of the vast quantity that fly about “in flagrante delicto” like your couple.  According to an online article we found written by D. Elmo Hardy:  “The family Bibionidae is poorly represented in the New Zealand fauna; only to genera have been recorded to date.  These are represended by six species of Philia and one species of Bibio.  the Bibio is an Australian species, but the Philia species are endemic and known only from New Zealand.”  It would seem appropriate that the name of the genus Philia has its root in Philotes, the Greek spirit of friendship and affection, or alternately, sexual intercourse.  The Brisbane Insect Website has images of mating March Flies that illustrate the large head of the male and the smaller head of the female, which is also apparent in your photograph.  This genus should not be confused with the biting Horse Flies that are called March Flies in Australia because of their appearance for a short time in March.

Letter 16 – Mating March Flies in San Diego


Now there’s MORE of them!
Hi again–
Wrote a few days ago when I was trying to identify this fly/wasp like bug. They were flying about in the hundreds–well now they are flying around nearer the thousands… …and today I saw a few pairs mating on the driveway. Noticed that one gender has a large head, whilst the other has a rather tiny one. I won’t venture near guessing which is male or female. They are not much more than 3/8″ long.
J Cannon
North San Diego County, CA

Hi J,
These are March Flies in the family Bibionidae and they are right on time. BugGuide has numerous images of mating pairs. The big eyed male has the bigger head. According to BugGuide, the larvae feed on decaying organic matter. There are several genera of March Flies, and we are not sure which your specimens belong to. The infamous Florida Love Bugs, Plecia nearctica, get so plentiful, and are often found copulating, so there is much information available online including on Wikipedia.

Letter 17 – March Fly from Australia


Black winged, orange bodied flying insect
Location: Downtown Sydney, Australia
October 22, 2010 3:33 am
I can’t find a photo that quite corresponds to this bug. It, and others similar, were apparently supping nectar from the same bush as lots of bees, hover flies and the like.
Seems to have a disproportionally small head. Attached photo shows 6 live views and three post mortem.
Signature: Mike Gordon

March Fly

Hi again Mike,
Upon seeing your new photos, we now believe the letter you sent last week contained a misidentification.  This is not a Sawfly, but rather, we believe, a March Fly in the family Bibionidae.  Unfortunately, the Brisbane Insect Website only contains images of a species that is not your insect.  Female March Flies often have significantly smaller heads and eyes than males.  Some confusion may arise as the name March Fly refers to Horse Flies in Australia.

Unknown March Fly from Australia

The new photos you have sent to us should enable a conclusive identification from an expert, but we are not having much luck finding any matches in our internet searching.  Perhaps one of our readers will provide an identification.

Unknown March Fly from Australia

Thanks, again, Daniel,
Following the lead that you have given me I think that I may have found it:
What do you think?

Another link:
Further defines the bug as female, as your email had suggested.

Hello again Mike,
Biblio hortulanus appears to be a European species as indicated on this UK Insect website and it may have been introduced to Australia, or your insect may be a similar looking but distinct Australian species.

Don’t think I’ll worry about that!

Letter 18 – St. Mark's Fly from the UK


Insect we saw hiking in England
Location: England, Yorkshire Dales and Yorkshire Moors
August 8, 2011 12:01 am
We saw these hiking in the moors where there seem to be moisture (standing water or mud) and some present of ferns, but not always. Late July, early August. These insects would fly about us and often in front of us as we walked. They did not appear to want to land on us but were ”curious” or looking for a mate? We saw pairs of these insects often buzzing around each other mid flight for short periods of time. We saw a few on the ground where they seemed to stay motionless for some time. A type of wasp? Thank.
Signature: Travelmarx

St. Mark's Fly

Hi Travelmarx,
This is a male St. Mark’s Fly or Heather Fly in the Bionidae.  Males have much larger heads and larger eyes than females.  You can see all the research we have done on this insect by viewing this old posting from our archives.  Related Flies in the southern U.S. are called Love Bugs because they are often found in the mating position.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. 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.

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  • 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.

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Tags: March Fly

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10 Comments. Leave new

  • Hi Karl:

    There are apparently 13 species of ‘March Flies’ in the genus Bibio listed for Great Britain. From what I can tell the closest match to yours is B. pomonae; the Heather Fly. It was the only one I could find with red colouring on the legs that doesn’t extend beyond the femur. The peak of the flying season in GB is July-August so the timing would be right. The species is very widely distributed in Europe, Iceland to Russia and down to the Mediterranean. According to some references it prefers higher elevations, hence the common name; others give hedgerows as the preferred habitat. The larvae feed on roots and the adults eat nectar, so I suppose your bites remain a mystery. For reference you could check out or Nice photos bye the way. Regards. K

  • Biblio marci
    Is the St. Marks Fly
    I hope you dont mind the correction

    • We welcome corrections at What’s That Bug? but we are hesitant to accept corrections that are not accompanied by either professional qualifications (are you a dipterist?) or by reputable links that clearly demonstrate the identification. We acknowledge that we are amateurs with no professional qualifications, and we attempt to the best of our ability to provide accurate information. Your “correction” substantiates both our original research and Karl’s comments that the March Fly in the images belongs in the genus Biblio and we understand that exact species identifications often require inspection of specimens by experts.

  • I have lots of these in my garden I find they fly around for a few weeks then just disappear after having laid their eggs on my Solomon seal plant which gets eaten after it has flowered and then it dies and all the little caterpillars just disappear until the end of March hence the name st marks

  • Hi Travelmarx,

    Your insect is the less common Bibio pomonae, the bright red femorae being a give-away.


  • Hi Travelmarx,

    Your insect is the less common Bibio pomonae, the bright red femorae being a give-away.


  • If they are much smaller, they must be Scatopsidae: They trick eyes by images.


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