Botflies and the perils of scientific research

Oct 29, 2013 by Elizabeth Wason
Credit: Lyle J. Buss

At first, Chris Dick thought the persistent ache in his ankle was caused by a thorn embedded in his skin. Made sense, seeing as he had done some work on a Pennsylvania farm around that time. An X-ray revealed nothing unusual, and the doctor recommended that Dick squeeze the foreign object out, once it worked itself toward the surface.

What Dick hadn't considered was his recent scientific expedition to Central America. An associate professor in the Department of Ecology and Evolutionary Biology, Dick collects data in the tropical forest on Barro Colorado Island, a Smithsonian research station in Panama. It just so happens that parasitic insects called botflies (Dermatobia hominis) love the place.

Botflies also love the place just under your . And they'll stay there, eating your flesh and growing inside you—in some cases, for several months. The stabbing pain that Dick felt in the protuberance on his was actually a botfly chewing through his flesh with its two sharp fangs, wriggling through his tissue. 

Rows of spines on the bulbous front end of the larva were gaining purchase, anchoring the creature's body under his skin. Had Dick looked closely, he may have been able to see the posterior end of the larva poking out of a small wound in his ankle, breathing air through its butt.

Botfly, Don't Bother Me

The botfly larva probably found Dick by riding a mosquito. When an adult botfly is ready to lay eggs, she pounces on a mosquito in midflight. She grips the mosquito and glues a bunch of eggs to its belly. Then she flees the scene to find another mosquito, and the egg-heavy mosquito resumes its search for blood meals in places like Dick's ankle. His body heat triggered a botfly egg to hatch, the hatched larva fell onto his skin, and the larva burrowed inside of him, head first. 

Left unmolested, a botfly larva would develop until it eventually emerged from the air hole that it drilled in the skin of its host. The larva would drop to the ground, pupate in the soil, and finally metamorphose into an adult fly.

Most people prefer to remove their parasitic insect invaders, however, and a couple of different methods of extraction exist. One tactic capitalizes on what we know of the creature's biology by exploiting its unique mode of breathing. A larva must occasionally venture its anal breathing apparatus through the surface of the skin to access the surrounding air.

A number of substances can be used to block the breathing hole—applying a thick layer of pork fat, ointment, beeswax, chewing gum, mineral oil, petroleum jelly, nail polish, glue, or duct tape can force the larva to evacuate the skin under threat of suffocation. Pork fat, or even a slab of meat, seems to work especially well, as the larva readily enters another substance that resembles animal flesh. Within about 24 hours, the larva migrates out of the skin and into the pork fat in search of air on the surface; the pork fat and the parasite can then be discarded.

Another method of pest control calls for the simple application of lateral pressure—popping the little beast out like a zit. Yet another option, albeit invasive and expensive, involves injecting anesthesia into the botfly larva and removing it surgically. Fragmentation of the insect can complicate these methods of forcible extraction; any piece of its body left behind can fester and cause an infection.

Dick used the popping method. One day in the shower, he noticed that the sore spot on his ankle was really red. He squeezed, and out came a writhing botfly. He scooped up the larva and kept it as a tropical ecologist's trophy; a scientist's souvenir.

Botflies, face-eating protozoa, giant pit vipers, and other hazards can't keep Chris Dick away from scientific research in the field. Why? Fieldwork allows him to investigate the remarkably improbable dispersal of tree seeds between continents by way of an inhospitable ocean. Tromping through botfly habitat, he can study the sexual reproduction of trees that are pollinated across huge distances in the forest. He has even discovered new tree species in the Amazonian jungle.

Discovery—it's worth an occasional parasitic larva crawling around under your skin. Right?

Explore further: Telling the time of day by color

Related Stories

Jumpy caterpillar shies the Sun (w/ Video)

Aug 21, 2013

The larva of a Vietnamese moth has devised a unique form of transport—constructing a leaf cone and thrashing about inside to make it jump, a study showed Wednesday.

Six human parasites you definitely don't want to host

Aug 28, 2013

Parasites are fascinating. They are uniquely adapted to survive, in some cases through very complex life cycles. There's also research to suggest that some may even change the behaviour of hosts to assist ...

New 'Moby Dick' lizard species found in Madagascar

Jan 15, 2013

A new lizard species has been discovered in Madagascar and named "Moby Dick" mermaid skink—after the albino sperm whale imagined by Herman Melville—for its flipper-like forelimbs and unpigmented skin, France's National ...

A real-life zombie story in the life of bugs

Jun 24, 2011

(PhysOrg.com) -- In a recent study published in Biology Letters, a page of science fiction comes to life in a real-life zombie scenario between the ladybug and a parasitical wasp called Dinocampus coccinell ...

Recommended for you

Telling the time of day by color

18 hours ago

Research by scientists at The University of Manchester has revealed that the colour of light has a major impact on how the brain clock measures time of day and on how the animals' physiology and behavior adjust accordingly. ...

Aphrodisiac for fish and frogs discovered

23 hours ago

A supplement simply added to water has been shown to boost reproduction in nematodes (roundworms), molluscs, fish and frogs – and researchers believe it could work for humans too.

Evolution puts checks on virgin births

Apr 17, 2015

It seems unnatural that a species could survive without having sex. Yet over the ages, evolution has endowed females of certain species of amphibians, reptiles and fish with the ability to clone themselves, ...

Humans can't resist those puppy-dog eyes

Apr 16, 2015

When humans and their four-legged, furry best friends look into one another's eyes, there is biological evidence that their bond strengthens, researchers report.

Roundworm parasite targets canine eyes

Apr 16, 2015

(HealthDay)—A small number of dogs and cats across the United States have been infected by a roundworm parasite that targets the eye, according to a new report.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.