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Botfly

life science Maturity 5-7 Next article →

Botflies are a group of insects belonging to the family Oestridae. They are known by several different names, including warble flies, gadflies, and heel flies. The term "bot" is actually a word used to describe a maggot. These flies are unique because their larvae are obligate internal parasites. This means the young larvae must live inside the bodies of mammals to survive. Some species grow directly within the flesh of their hosts. Other species live inside the alimentary tract, which is the host's digestive system.

Ox Warble-fly
Ox Warble-fly

The life cycle of a botfly involves several specific steps to ensure survival. A female botfly has a very short adult life, lasting only 8 to 9 days. During this brief time, she can produce between 100 and 400 eggs. To distribute these eggs, she often uses an intermediate vector. A vector is a middle insect, such as a mosquito, a housefly, or a tick. The female fly captures the vector by holding its wings with her legs. She then attaches 15 to 30 eggs to the abdomen of the insect.

Ecuadorian mantled howler (Alouatta palliata aequatorialis) juvenile male with botfly (Oestridae sp.)
Ecuadorian mantled howler (Alouatta palliata aequatorialis) juvenile male with botfly (Oestridae sp.)

When these eggs come into close proximity to a large mammal, the host's body heat stimulates them to hatch. The larvae then drop off the vector and burrow under the animal's skin. In some cases, eggs are deposited directly onto the skin of a large animal. Other species involve the larvae being ingested through licking. Once inside, the larvae develop within the host. They do not kill the host, which is why they are classified as true parasites. After they reach maturity, the larvae drop from the host and complete their pupal stage in the soil.

Magendassel
Magendassel

Different species of botflies target different animals in specific ways. Equine botflies, for example, affect horses by laying eggs on the legs or the nose. These eggs look like small, yellow drops of paint and adhere to the horse's hair. If a horse rubs its nose on its legs, it can transfer the eggs to its mouth. From there, the eggs move to the intestines. The larvae grow there for 10 to 12 months, attaching to the stomach or small intestine lining. This attachment causes irritation, erosions, and ulcerations.

DeerBotFlyReaumur
DeerBotFlyReaumur

In cattle, botfly infestations can lead to more serious medical issues. The lesions caused by these flies can become infected by a bacterium called Mannheimia granulomatis. This infection causes a condition known as lechiguana. Lechiguana is characterized by the rapid growth of hard lumps beneath the skin. If the affected animal does not receive antibiotics, it may die within 3 to 11 months. To manage these flies, owners can use various dewormers, such as ivermectin, dichlorvos, or trichlorfon. Other species, like the mouse botfly (Cuterebra fontinella), target small mammals across North America.

Humans have a long and surprising history with these insects. The species Dermatobia hominis is the only botfly known to parasitize humans routinely. However, humans have also used botfly larvae as a food source in certain cultures. In cold climates, populations that rely on caribou or reindeer have historically eaten the maggots. Survival expert Les Stroud observed Inuit guides eating a larva during a hunt on Baffin Island. He noted that the larva tasted like milk. This practice is supported by very old art from the Pleistocene era in Europe.

Ecuadorian mantled howler (Alouatta palliata aequatorialis) juvenile male with botfly (Oestridae sp.)
Ecuadorian mantled howler (Alouatta palliata aequatorialis) juvenile male with botfly (Oestridae sp.)

Beyond simple biology, botflies appear in many different human records. The Babylonian Talmud even includes discussions regarding whether the warble fly is kosher. This shows how deeply these insects are woven into human history and law. There are roughly 150 known species of botflies found throughout the world. While the Oestridae family contains the highest proportion of mammal parasites, other fly families also cause myiasis, which is an infestation of larvae. For example, blow-flies are members of a related family that can also cause similar issues in humans.

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🖼️ Images & Media (4)
File:Ecuadorian mantled howler (Alouatta palliata aequatorialis) juvenile male with botfly (Oestridae sp.).jpg
Ecuadorian mantled howler (Alouatta...
File:Magendassel.jpg
Magendassel.jpg
File:Ox Warble-fly.png
Ox Warble-fly.png
File:DeerBotFlyReaumur.jpg
DeerBotFlyReaumur.jpg
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