Currently viewing the category: "Bot Flies"
What's That Bug? does not endorse extermination

Black and White Bumblebee-Like Relative Found near Yosemite? Sat, Apr 11, 2009 at 3:12 PM
This might be some sort of mutant insect, because it certainly beats me. I found it rolling amongst the pebbles outside my mountain home near Yosemite, where many common bumblebees and honeybees flourish. Something is definitely off… Instead of mouth parts it has nostril like holes and the flesh above the undersized wings (it cannot fly) appears withdrawn, or peeled up.It’s first two segments have a white furry underbody and a shiny hard top. It’s last segment is shiny and hard. It has no antennae. It’s eyes are black with two red spots, one on the top and the other on the bottom portion. I figure mutations might not be your forte, but is this just a really weird insect? He’s also about an inch long.
Interested Mountain Girl
Coarsegold, near Yosemite Valley, CA

Rodent Bot Fly

Rabbit Bot Fly

Dear Interested Mountain Girl,
We wonder how long you are going to maintain your interest when you learn that though it looks like a Bumble Bee, this is actually a fly, a Bot Fly to be exact. We believe it is a Rodent Bot Fly. Bot Flies are endoparasites of various mammals and they cause swellings knows as warbles, giving the Bot Fly the name Warble Fly as well. Rodent Bot Flies tend to parasitize squirrels and rabbits. In Central America, there is a Human Bot Fly.

Wow, this is actually even cooler. I hadn’t realized we had those here, but I’d not paid much attention to the insect and bug life since I moved here a few years ago. Sorry for the poor picture quality, the camera wasn’t working at it’s best, but thank you for the amazing and prompt response, you guys really are amazing bug people!
Right now my little Bot buddy is in a glass jar with a damp paper towel and a few leaves, and he seems to be getting more active by the hour! I’ll free him pretty soon, and he can go back to his biting, buzzing ways, much to the chagrin of the local voles and bunnies.
-Interested Mountain Girl

What's That Bug? does not endorse extermination

Sorry to hassle you again after sending the glowing scorpion
from the Grand Canyon, but I thought you might want some cuterebra
photos too. I am a veterinarian in Colorado Springs,
CO, and I commonly see cuterebra larvae (my personal favorite
clinical entity) in dogs, cats, ferrets, and rabbits from
late July to early September. The pet usually has a
mound on the skin with a perfectly round hole on top through
which you can see the larva moving. Sometimes there
is a little discharge, but in general it does not seem to
be too irritating. Imagine the surprise when the owner
squeezes at the mound and out pops this little larva!
It sure is dramatic, but they don’t really cause any
serious health problems. When I see them I use a little
local anesthesia around the opening and then enlarge it with
a scalpel blade before gently squeezing the larva out because
the hole is often smaller than the larva and if you are too
forcefull you can squeeze the larva inside out, leaving the
cuticle to fester under the skin. It is unusual for me to
see more than one on a pet at one time, since most pets
are not the preferred hosts, but this little Yorkie had
10 of them. The owners squeezed most of them out themselves
(thus taking away all my fun) and fortunately all the larvae
came out intact for them. Cattle also have a cuterebra
species that affects them and the common name for the
condition is ‘Warbles’. The quick and dirty way to get
rid of the larvae in cattle is to place a soda bottle upside
down with the mouth over the opening and then quickly hit
the bottom of the bottle so that the larva shoots up into

Hi Anne,
Getting such an informative letter would never be a hassle.
Thanks for your expert account of a Bot Fly Larvae infestation
and treatment recommendation. The typical hosts for North
American Bot Flies are rodents like rabbits and squirrels.
There is a Human Bot Fly found in Central America.

What's That Bug? does not endorse extermination

Squirrel insect
These grubs or insects showed up in my cabin along with a dead squirrel the cat brought in. Could be that its a coincidence or perhaps the cat brought them as an additional gift. The insects were not on the squirrel. Can you help me identify these so I can decide weather they a friend or foe.
Rick in Western Colorado

Hi Rick
Here is one sure to gross out our readership. These are Rodent Bot Fly Maggots, Cuterebra species. The Rodent Bot Fly is a mammalian endoparasite. According to a website we located: “The female flies will lay their eggs along rabbit trails and near rodent burrows. The first stage larvae will hatch and quickly attach to hair when a host brushes against the egg. The larvae then burrow into the skin and leave a breathing hole. ” Also on the website is the information: “Cuterebra is a normal bot fly of rodents and rabbits, but can also infect cats, dogs, and man. The adult fly looks like a bumblebee and is rarely seen. It may appear a shiny blue or black color. The third stage larva is dark brown to black with stout black spines. ” Your close-up photo shows the mouth hooks of the maggot, substantiated by this image on BugGuide. Bot Flies are also known as Warble Flies due to the lumps visible on the skin of the hapless host. There is also a Human Bot Fly, Dermatobia hominis, that is found in Central America.

Wolves on Rabbits
After just reading your description of the bot fly larvae, I’m wondering…at certain times of the year (usually late summer, early fall) when my father would go rabbit hunting, (we actually depended on them for food in the ’50’s), they would sometimes get rabbits with what they then called ‘wolves’ in their necks and we were not allowed to use them for a food source. Could it be that I’ve learned after all these years that these were actually bot fly larvae? I large lump would most times be visible. Does this actually damage the meat for human consumption? Thanks for taking the time to read my query and if you have time to answer, that would be great, but if you don’t, I understand…. Sincerely,
Pat, Hawk Point

Hi Pat,
It sounds like your rabbits with wolves were parasitized by a Bot Fly. The meat near the wolf or warble might be unsavory, but cooking the meat would definitely kill the parasite.

Joanne Gets Sick!!!(08/15/2007) The Rodent Bot Fly
Will you pay for cleaning my nice leather recliner cuz I just barfed on it.

Close Encounter with a Human Bot Fly!!!
(08/15/2007) Human Bot Fly experience
Hello fellow bug-nuts,
Your recent posting of the rodent bot fly larvae brought back some interesting memories. I brought an unexpected souvenir home from a trip to Costa Rica in ’00. You guessed it. Luckily, I’d read about these critters. Made me the hit of my local doctor’s office. I actually printed a page from a Canadian website and brought it along in to prove I knew what I was talking about. It is a very weird sensation to feel these beasts move when they’re in your flesh (mine was in the flab of my upper left arm). You can actually feel the bristles they anchor themselves with as they twist about. The research I did told me the adult female bots actually wrestle a mosquito down and lay an egg on the mosquito’s abdomen. Then the mosquito bites a host, the egg on her belly hatches (very quickly, apparently), and the newborn enters the mosquito’s bite site. My research also gave me the bot’s larval timeline, so I knew how long I had, and how insistent to be at the doctor’s office. Love your site! I check it every day.
Don J. Dinndorf
St. Augusta, MN

Bot Fly Larvae are Edible
edibility update on bot fly
Hi Daniel,
Just to keep the gross-out fest going, and to answer Pat’s question: I’m pretty sure that NO, the presence of bot fly larvae would not render the host animal inedible. There’s a good deal of documentation [as recent as 1918] of Inuit hunters taking down caribou that were infested with large fly larvae, and then making a point of cooking and eating the larvae first. Not sure if I could do it, especially considering the textural issue of those rough, stubble-like projections all over the larvae’s sides, but the point is that if some people enjoyed eating the actual flesh-consuming maggots, then eating the rest of the animal would not be a big deal. Reluctance to do so is pure ‘fussiness’ on our part. Best,

What's That Bug? does not endorse extermination

Hey Bugman,
Love your site and use it a lot. I believe this is a new born
Carpenter bee. I watched and listened to a Queen bore a nest in the railing of my deck this spring. This morning I found this on a leaf below where the hole from the nest is. I thought I would share with you and your followers these pictures of a new born. It has quite a “cute” pig like face and exclamation points in it’s eyes. Thank you,
Chicago, Illinois

Hi Glenn,
You are mistaken in your identification. This is not a bee, but a fly. It is a Bot Fly to be exact. Bot Flies are mammalian endoparasites. There are species in the tropics whose larvae live inside human hosts, but the North American species are parasitic on rodents. They are also called Warble Flies. Eric Eaton has this to add: “Hi, Daniel: The bot fly is another species in the genus Cuterebra, the rabbit and rodent bot flies. The red in the eyes is characteristic of some species. Don’t know if there is a good website on them, but there is a great technical book on them with some nice images and lots of information on their bizarre biology…. Eric”

What's That Bug? does not endorse extermination

What the Hell is This!!!
Please Help!
This is probably one of the sickest stories you’ll come across.. It was like a scene out of “Aliens”. This morning, I came across our pet greyhound, Merlin, calmly sitting in our family room, with what appeared to be a rather large, dead rat in his jaws!!! He immediately dropped it, once I told him to. Our back yard, while fenced in, is bordered by wooded areas. Consequently, we do get the occasional mouse or rat in the yard. The rat, upon further inspection was not dead. It was fairly mangled up and appeared to be taking its last gasps of air. I grabbed a plastic bag and like picking up dog poop, grabbed the rat by the tail and took it out back. My wife, by this time, had joined me and the initial shock of finding such a large, disgusting “present” in the house had slightly abated; we were quite impressed by its size. As I turned the rat around by the tail, I thought I was looking at internal organs that were beginning to “protrude” through the puncture holes and small lacerations on the rat’s body. . . . To my and my wife’s horror, we realized that these were not organs, but large writhing “things” (grubs, worms, maggots)!!!!????, boring their way out of the body. I quickly disposed of the “present”, but not before one of the things in question, dropped to the pool deck, where I scooped it into a plastic bag for identification. . . . Since we have no idea what this thing might be, my wife is now worried that our beloved grey may have swallowed or eaten one of these creatures and that at this very moment, it is making a lovely home for itself and its larvae in the body of our greyhound. Doubtful, but I am passing along the concern. If you can make out the picture, it is segmented and colored a dark- greenish black. Tried to identify it myself, but had no luck. Hope you can help.
Palm Beach Gardens, Fl.

Hi MP,
Based on just your vivid description, we would identify your creature as a Rodent Bot Fly, Cuterebra emasculator. This fly which resembles a Bumble Bee lays its eggs indirectly on habitat and the warmth of the rodent body causes the eggs to hatch and the maggots to attach to the host animal. The maggot then enter the rodents body through an opening, either being licked inside or by boring through the eye membrane. It then settles beneath the skin and forms a warble, a type of pimple through which the parasite can breath and excrete. The parasite is rarely transfered to another host, and the risk to predators is minimal. Just to add to your nightmare, there is also a Human Bot Fly, Dermatobia hominis, reported from Central America. We have not been able to locate a photo of the Bot Fly Pupa, but your image is consistant with fly pupa, and the supporting story lends credance to our identification.

What's That Bug? does not endorse extermination