Bot fly: Description, Horse Botflies, Impact, Cycle of Life and Control

Bot Fly: Definition

Bot fly (family Oestridae), often spelled botfly, is any member of the Diptera order whose adults have a beelike look and are hairy but lack bristles.

Botflies are huge, hairy insects with thick bodies that resemble bumblebees. A mosquito, or occasionally another bug, lays the botfly egg. The larva grows until it is rather enormous inside the host’s body. Adult botflies do not feed since their mouthparts are nonfunctional. In most cases, the parasite does not cause significant harm to the host. When the larvae depart the host through the warble, the majority of the damage occurs. The botfly’s parasitism has little effect on the rabbit’s edibility (if you eat rabbit), and the area adjacent to the warble is usually clipped away, leaving the rest of the rabbit edible.

Horse Botflies

Gasterophilus, a major horse pest, is found among the horse bot flies (subfamily Gasterophilinae). The adult horse fly, also known as the gadfly, lays 400 to 500 eggs (nits) on the forelegs, nose, lips, and body of the horse. The larvae stay in the eggs until the horse licks the eggs clean. The larvae emerge and are eaten when they are stimulated by moisture and friction. They attach to the horse’s stomach or gut lining and get all of their nutrition and oxygen from the alimentary canal. After 8 to 11 months, the larvae reach maturity and are expelled through feces. Each larva produces a distinct lump, known as a warble, from which a cattle grub emerges.

Horse bots are bee-sized flies that lay their eggs in the hairs of horses’ bodies, most commonly on their legs. Horses eat the newly hatched larvae, which dwell in the mouth and stomach lining of the horse. They are passed out by feces after many months. Oestrinae members are known for their quick flight; they can travel at speeds of 20–30 kilometers (approximately 12–19 miles) per hour.

Cuterebra cuniculi, which infects rabbits, and Cuterebra emasculator, which assaults squirrels’ scrotum and sometimes emasculates them, belong to the Cuterebrinae subfamily. Dermatobia hominis, the human bot fly, preys on livestock, deer, and humans. The female attaches her eggs to mosquitoes, stable flies, and other insects, which then transport the eggs to the intended host. The eggs hatch and the small larvae enter the skin as a result of the body’s warmth. Dermatobia is to blame for cattle and hide losses in tropical America.

Impact on the Horse:

1. Harms the tissues of the mouth and stomach lining

2. Gastroesophageal ulcers

3. Inflammation of the stomach lining, which can lead to: o nutritional deficiency o food obstruction (raising the risk of colic)


A tool called a ‘bot knife’ should be used to remove botfly eggs from the horse’s coat. Because adult flies die in cold temperatures, this will keep the horse from becoming infected again.


The horse bot fly was first discovered in Hawaii in 1906, and the horse throat bot fly was discovered in 1908. Although the horse bot fly is more abundant than the throat bot, both species are found in connection with equines on all Hawaiian islands.


Botflies are 2 to 3 inches long and have black and yellow hairs covering their body, similar to bees. Both insects lay whitish eggs that are adhered individually to the hairs of the mammal. Horse bot fly eggs hatch on the animal’s forelegs, belly, flanks, and shoulders, whereas horse throat bot fly eggs hatch beneath the chin. The larvae are off-white, 12 inches long, blunt, and spine-ringed.


1. Horses, donkeys, and mules are examples of these animals.

2. Concern for livestock

3. Ulcerated stomach, chronic gastritis, loss of condition, and, in rare situations, death from peritonitis are all possible side effects.

Cycle of Life

Female botflies lay 150–1000 eggs on the host’s body while hovering, and the eggs hatch in 4–5 days. After being licked or bitten by a horse, the larvae of the horse bot fly hatch. Horse throat bot fly larvae do not need to be bitten or licked to hatch. Young larvae move up into the mouth of the animal, burrow into the tongue, and feed for around 28 days.

Larvae move from the mouth to the stomach, where they attach themselves to the wall for 9–12 months before passing out with the feces and pupating in the dung. After 2–8 weeks, adult flies emerge from the dung.


Adult fly emergence sites can be removed by cleaning up and disposing of horse dung. To get bot eggs to hatch, clip them from the horse’s hair or sponge them with warm water. Ivermectin or organophosphate pesticides can be used to control stomach bots.

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