The Human Botfly: You Take Your Lumps!

It ain't pretty, but at least it's sickening!

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hideous photo of larvae emerging from wound.    animal
hideous photo of larvae emerging from wound. animal

The Cuckoo of Predatory Insects


Dermatobia hominis, take a bow!

Anyone who can stand my articles know I am immune to creepy-crawlies, at least semantically. These little insects and arachnids are certainly interesting and it behoves us to know something about them in order to be on our guards when in their territory.

Tonight’s protagonist is one you won’t meet often in the chill of the temperate countries, such as Europe and most of the United States - although many creatures are spreading these days, hiding in cargo on ships and international flights. Britain, for example, has had a few surprised folk turning up in the emergency wards having been bitten by an “unusual” spider which turned out to be one of the world’s most dangerous arachnids, the Brazilian Wandering Spider, which had far exceeded it’s usual wandering habits. So far, no one has died from a globe-trotting venomous creature in the UK anyway; it’s probably only a matter of time.

But tonight’s “nastie,” the Human Botfly, prefers the tropics with their heat and high rainfall. They are in Mexico, and all points south, which means there’s little stopping them from infiltering the USA; the alien fence can’t even stop 200 pound wetbacks; the botfly will merely chuckle as it flies over it and insouciantly drops a few maggots into one of the ‘migra. Specimens of the 150 known species have also been found in Canada, Hungary, New Zealand and parts of Africa - whether these are of the human botfly variety I am not sure (this is the only member of the species which preys on man).

But botflys are different than most of the blood-suckers we have looked at the past several months. They don’t actually come near us nor the other large animals their larvae preys upon. This clever little cuckoo of the insect world has an accomplice, albeit an unwilling one.

When the female botfly is ready to lay its large eggs, it uses its speed and strong flight to capture a female mosquito. A female mozzie, because the males never bite humans, only Mrs Mosquito; the males feed on plant sap.

Once the botfly has a mozzie in its power, it lays its 10 to 30 sticky eggs on the mosquito where they become attached. The mosquito does what female mozzie do, finds a human or animal blood meal. As it pushed its proboscis into the flesh, some or all of the botfly eggs become detached, quickly release the larvae, one of which enters through the hole made by the mosquito. This remains near the entrance hole which it need for oxygen and begins feeding on the host’s living tissues. The larvae soon begins to grow and the area quickly becomes irritated from its saliva and excreta as well as from the host’s natural defences. A hard lump soon becomes apparent; if the botfly larvae is untouched, as it often is in cattle and other wild animals, it will stay for more than three months before enlarging the entrance hole and crawling out to drop to the ground and move on to pupate in the soil.. In humans, the larvae is usually removed in a minor, out-patient operation.

Botflies have also been reported using houseflies as vectors to carry their eggs/maggots. One variant, the Warble Fly, which commonly preys on caribou and reindeer has its maggots removed when northern natives butcher the animals and they are eaten as a delicacy: rather like wichetty grubs in Oz, or the gusanos de maguay in Mexico.

Botfly eggs and larvae can also be eaten by the host animal and reside in the gut until they are mature and passed in the animal’s excreta. This is particularly disturbing in domestic horses (see below).

Another specialist botfly concentrates on small mammals, such as rats, generally not doing enough damage to kill the host, but, in some cases, eating the testes and/or ovaries! I am indifferent to rats; rather admire them if anything, but I pity those picked on by the botflies.

Notes for Horse Lovers

Botflies can be a particular menace to equestrian caretakers as they lay their eggs in difficult to clean places like the cannon bone and must be removed before horses locate them and lick them off, passing them into the intestinal tract. They look like tiny drops of yellow paint. Wikipedia has some info on this.

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Comments 20 comments

Hello, hello, profile image

Hello, hello, 7 years ago from London, UK

Some more interesting information I have learned. Thank you

diogenes profile image

diogenes 7 years ago from UK and Mexico Author

Hello, Hello hello: A loyal reader, indeed, may you be ever safe from the botfly! Bob

Amanda Severn profile image

Amanda Severn 7 years ago from UK

Bob, yet another scary addition to your on-line encyclopedia of disturbingly nasty creatures that I'd never previously heard of! You should publish these in a book so that I could buy it and put it in my son's Christmas stocking. This is exactly the kind of thing he loves to read about!

diogenes profile image

diogenes 7 years ago from UK and Mexico Author

Well, there are books on the market...but that's not a bad idea. I got burned recently publishig some books, which is shown in my hub, "Rosalind Franklin is a Thief," if you'd like to have a look. May all your botfly bumps not itch! Bob x

Lady Guinevere profile image

Lady Guinevere 7 years ago from West Virginia

I couldn't read all of your hub, just yet. I know all about the Botfly. I had a rabbit that had one once and they were disgusting little creatures.

diogenes profile image

diogenes 7 years ago from UK and Mexico Author

Thank you so much for at least sampling the Botfly story until your tummy turned! They are indeed nasty little beasties, they shouldn't really be a problem to man because of our awareness and ability to check our bodies; a few get past, though. Poor bunny, hope you evicted the painful lodger. Bob

Lady Guinevere profile image

Lady Guinevere 7 years ago from West Virginia

It was a long time ago and yes the Vet got it out without any harm to the bunny. They are gross little cratures. We don't know why she got one and none of the other bunnies did. It was while I lived in Florida. Never heard of them while living in Virginia..not until we moved to Florida.

diogenes profile image

diogenes 7 years ago from UK and Mexico Author

Most mammals, except man, are helpless when faced with insect predation; our problems come from smaller creatures like bacteria and viruses, and mosquitos of course which are so numerous they can overwhelm. I think the botfly is so nasty because of the size of the larvae... Bob

lOUISA 7 years ago

Hello Diogenes - Thank you very much for the information here about botflies. I live in the UK and I have recently been bitten near my eye. My children have been learning about the botfly and are totally freaked out by the swelling to my eye, hence my need to do a little research as to whether there has been any cases in the UK?

Thank you.

Nick 6 years ago


I recently spent some time in the Ecuadorian Amazon rain forest.

Since returning to the UK, one of my friends from the camp was telling me of a spot on his back which he was sure he coud feel something crawling inside when he went to bed. I told him it was probably nothing to worry about.

A few days ago, he had the spot squeezed and out popped a botfly larvae!

Another leader on the expedition had experienced a botfly inhabitation out in the field.

I have not discovered anything crawling ubnder my skin just yet, but I'm keeping an eye out!!

I get the impression that although unpleasant, the risk from these critters is minor unless they are either laid in vunerable areas or cause infections. I'd rather have the botfly than malaria.

kimh039 profile image

kimh039 5 years ago

Hi diogenes. I just left you some fan mail. I was going to write a hub on the human botfly, and I was pleased to discover that you have already tackled that most disgusting task. Thank you! Yuck.

diogenes 5 years ago

I'm sure there's room for another one! Bob

kimh039 profile image

kimh039 5 years ago

Diogenes, I even went so far as to write a hub on Dr. Bugs and still couldn't bring myself to put this video on my hub. I bequeath it to you to do with as you will. (It doesn't actually belong to me, so I can't actually bequeath it. If I could I would though.) Warning: It's disgusting.

diogenes profile image

diogenes 5 years ago from UK and Mexico Author

Nice of you, dear, your Mother's day present is in the mail of several botfly larvae...careful how you open it!

Just kidding Kim, really, very thoughtful. I never use videos but I might with this one...Bob

diogenes profile image

diogenes 5 years ago from UK and Mexico Author

...great video, Kim: it would take some fortitude to allow one of those beasties to grow in your body...Bob

kimh039 profile image

kimh039 5 years ago

it takes some fortitude to watch a video of someone else allowing one of those beasties to grow in their body!! Yes, please cancel the Mother's Day gift.

Debby Bruck profile image

Debby Bruck 5 years ago

Dear Diogenes ~ I found this one on Botfly fascinating. Both my son and his friend has these critters lay eggs under their skin. when they went to the doctor, the fly flew out. It was quite gross that these large lumps were itching and infected spots. That's what you get when you live in South America. Blessings, Debby

Alicia 4 years ago

Great information. as soon as i heard about this nasty creatures i wanted to learn more about eewww its scary.. I must said i do found offensive your comment about the boder not stopping wetbacks. im mexican and i do not aprecciate when people use that term.

diogenes profile image

diogenes 4 years ago from UK and Mexico Author

Hi Debby. At leat the botfly larvae is easy to spot, other nemesese, such as Chagas via the Reduvvid Bug, isn't. As you say, the perils of the tropics.


diogenes profile image

diogenes 4 years ago from UK and Mexico Author

Alica. Hola preciosa: Thanks for visit. Believe me, I'm on your side, actually and figuratively, not designed to offend.


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