Horse flies are infamous for having one of the most painful bites in the insect world. The females use razor-sharp mouthparts to slice through the skin of humans and animals alike, leaving sore (and often irritating) wounds in their wake.
Horse flies can be tricky to eliminate completely, but understanding more about the various stages of their life cycle and breeding habits can help you to get their numbers under control.
What’s a horse fly?
Horse fly is the common name for biting flies in the Tabanidae family. This enormous group is made up of over 4400 separate fly species, and members of this family are also often referred to as deer flies or yellow flies.
Horse flies can be found almost everywhere and are often a major pest of both humans and livestock.
One of the world’s most dreaded summer pests, horse flies are generally reviled for their painful bite and their persistence – once they’ve locked onto a target, they rarely let up until they’ve tasted blood!
Female horse flies have one of the nastiest bites in the insect world thanks to the sharp, knife-like mouthparts they use to slash at the skin of their victims. They feast on the blood that pools in the resultant wounds, releasing salivary secretions that can cause further itching, inflammation, and discomfort.
Horse fly bites may also cause allergic reactions in some people and, if scratched, can lead to skin infections. They also often hop from host to host, so they may spread human and animal diseases when feeding.
How long do horse flies live?
The adult horse fly lifespan is mercifully short, with most surviving for just 30-60 days.
This represents only a small portion of their total lifespan, however, and the entire life cycle of most horse fly species takes one year to complete.
What is the horse fly life cycle?
The life cycle of the horse fly is divided into four distinct stages: egg, larvae, pupae, and adult.
Like all other insects, horse flies start their lives as eggs.
Horse flies lay their eggs in clusters that can contain anything from 100 to 1000 individuals. The eggs are cylindrical in shape and creamy white when first deposited, but they quickly darken and become gray or black in color.
They prefer to lay their eggs on the vertical surfaces of aquatic plants, though they may also lay eggs on sticks and rocks.
Horse fly eggs typically take between five and seven days to hatch, depending on the surrounding environmental conditions.
Once hatched, the horse fly enters the first of 6 – 13 separate larval stages which may be aquatic, semi-aquatic or terrestrial (depending on the species).
Most species of horse fly overwinter in their final larval stage, which molts into a pupae once spring rolls around.
Horse fly pupae are brown in color and elongated, with a rounded front end and a tapering back end.
The pupal stage of the horse fly can last anywhere from 3 to 6 weeks, after which the adult flies emerge.
Once the pupal stage is complete, the adult horse fly emerges. Adults horse flies are large (10-25 mm long) with brown-ish, hairy bodies and clear or smokey wings.
The adult phase of the horse fly lifecycle is the one you’re most likely to encounter, though only the females can bite.
Their mouthparts are stronger than those of the males, which largely feed on nectar. This is because, like mosquitoes, female horse flies need blood in order to develop and lay their eggs.
How can you control horse flies?
Adult horse flies have an excruciatingly painful bite and can be a major pest for both humans and animals.
If you regularly encounter these bloodsuckers during summertime, you may want to consider implementing control measures to cut their numbers.
Remove their breeding sites
Horse flies love water and seek out pools to breed, feed and drink. Female horse flies often prefer to lay their eggs on aquatic plants, and will also wait here for host animals (like horses and cattle) to approach.
You can, therefore, reduce the number of horseflies on your property by eliminating water sources, where possible.
If you keep livestock, pay extra attention to the areas around animal watering sites and maintain good drainage around areas that may collect excess water.
You can protect yourself and animals from horse flies in the home by installing screens around doors and windows.
Personal protection from horse flies
Avoiding horse fly bites this summer is easy, so long as you take the appropriate protective measures.
Long, loose-fitting clothing and bug spray (containing DEET or other insect-repelling ingredients) can keep horse flies (and other biting bugs) from getting at your skin.
Sticky paper and traps
Hanging sticky paper and setting out traps can also help to reduce a horse fly population.
Set these up wherever you notice high levels of horse fly activity.
If your horse fly situation is getting out of hand, you might want to implement chemical control measures.
Insecticidal sprays, fogs, and mists can kill large numbers of flies at once (especially in enclosed spaces) and residual insecticides may be used in barns and sheds.
These are usually applied to walls and ceilings where flies rest, killing any bugs that come into contact with these surfaces.
Horse flies are renowned for their aggression and the painful bites they inflict on their hosts. They are a major pest of horses and cattle, but they will also bite humans (and any other blood-filled creature they can find).
Horse flies pass through four distinct life stages: the egg, larvae, pupae, and adult fly. For most species, this sequence takes about one year to complete in full, though adult horse flies typically only live for 30-60 days.
They are highly attracted to water sources as this is where they usually mate, lay eggs, drink, and feed. You can, therefore, keep their numbers to a minimum by eliminating unnecessary water sources around your home.