Spring comes again every year. And just because there’s a pandemic going on, that doesn’t change. And with spring, comes pests. But some of the worst of these are the Florida biting flies that infest the air itself. That’s why we’ll discuss a few species of them today.
Biting Flies: Overview
As the weather warms up, you’ll notice a few annoying species of biting flies fill the air. Some of them range in just smaller than a housefly, all the way to the flying tank that is the horse fly. We’ll start with the tank.
Horse flies
Horseflies are large, biting pests that grow from about half an inch to an inch and a half long. They’re usually gray or black in color and have large and shockingly pretty green eyes. They all have antennae that are shorter than the length of their head. The females of this species have blade-like mouthparts. These blades slash the tissue and blood vessels of your skin and cause blood to bubble up to the wounds. Females then essentially dab their sponge-like mouthparts to suck up the blood. Males have similar mouthparts, but are much weaker and tend to only feed on pollen and nectar.
these Florida biting flies are similar to deer flies, and both are in the family Tabanidae. The two ways to tell them apart is to look at their overall size and their wings. Horse flies tend to be much larger with a stouter body and a very large head with very large eyes. Their wings are usually clear or cloudy whereas deer flies have dark bands or spots across their wings.
Horsefly bites are painful and may cause allergic reactions and at times secondary bacterial infections if the bite is not properly treated. However, the blood-sucking pests are not frequently implicated in disease transmission, unlike mosquitoes and ticks. Insect repellents rarely deter horse flies.
Female horse flies feed on the blood of humans and other animals, while the males do not feed on blood. These pests can detect humans by movement, color, or carbon dioxide output. They do not feed indoors, but sometimes enter homes on accident through open windows and doors. These flies are only active during the day and are usually more abundant in the summer and around pools, lakes or other bodies of water.
Deer Flies
Cousins of the horse flies, the deer fly adults range from about a quarter to a third of an inch long. These Florida biting flies’ wings are clear and have dark bands or patches on them. Their bodies are gray or light brown, but some species have bee-like black and yellow stripes. They have large, brightly colored eyes much like the horse fly as well. Their antennae are usually longer than their head.
Much like the horse fly, the deer fly feeds on the blood of humans and other animals. They come out in warm weather and rely on color, movement or carbon dioxide output to find hosts. The pests rarely enter homes because they prefer moist habitats like marshes, woodland ponds, and streams and there are very few practical methods that will prevent or control deer flies around the home.
Biting Flies: The Bites
Horse flies rarely bite near the head. Horseflies have a range of hosts that include mammals of almost all sizes, livestock, humans, pets, and birds. Should a female horse fly be interrupted when attempting to feed, they will fly off but quickly return to bite again, or go to another host to consume a complete blood meal.
Deer flies use their sharp mouthparts to inflict painful bites. While they do not usually have long-term effects, bites can cause allergic reactions in some people. In addition, deer flies occasionally carry diseases like tularemia and can transfer disease to humans through the deer fly’s bite.
Female horse flies usually bite large, nonmoving mammals on the legs or body. Deer flies, in contrast, attack moving hosts and typically target high on the body, like the head or neck.
Symptoms
When bitten, the symptoms and bite reactions can include:
- Localized swelling and an itchy red area around the bite.
- Persistent itching and scratching of bite wounds that can cause secondary bacterial infections if the bite is not kept clean and disinfected.
- Since horse flies inject anticoagulant-containing saliva during blood feeding, some serious reactions may occur in people that are highly allergic to the anticoagulant compounds. Symptoms may include a rash on the body, wheezing, swelling around the eyes, swelling of the lips and dizziness or weakness.
Can they transmit diseases to humans?
Investigators have isolated many viruses, bacteria, and protozoa from the sponge-like female mouthparts and their digestive system, but no studies to date show conclusive evidence that horse flies are capable of trans¬mitting diseases to humans.
Disease transmission to livestock is another matter. Adult flies may pass a number of disease agents and nematode parasites to animals. Equine infectious anemia (EIA), sometimes referred to as swamp fever, occurs in the southeastern United States and is mechanically transmitted to horses and other equines by horsefly bites. Symptoms in animals include lethargy, weight loss and sometimes death.
Reproduction & Life Cycle
Horse fly development sites are freshwater and saltwater marshes and streams, moist forest soils and even moist decomposing wood. Females usually deposit egg masses on wet soil or vegetation that overhangs the water. Larvae are active in moist or wet organic matter and look similar to house fly maggots.
Horseflies have from 6-13 larval stages, depending on the species. The final larval stage overwinters and then enters the pupal stage in the spring. The pupal stage only lasts about 1-3 weeks after which the adults emerge in the late spring or early summer. Fertile females will lay their eggs on the underside of leaves, and in about 2-3 days the larvae hatch out and drop from the leaf. Most horse fly species have only one generation per year, but others may take up to 2-3 years to complete their development.
Horse fly larvae vs deer fly larvae
Horse fly larvae studied by field researchers feed on midges, crane flies and even other horse fly larvae. Because of their cannibalistic behaviors, horse fly larvae are usually found living alone. Deer fly larvae, on the other hand, usually live in groups. Pupae do not feed.
Female horse flies must consume a blood meal in order to yield fertile fly eggs. One female can lay from 100-800 eggs per year. That’s a lot of Florida biting flies!
