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

Subject: Black bug
Location: Gunnison, Colorado
July 21, 2014 5:08 pm
I found this bug in my home. I thought it was a bee at first but then with a closer look it seemed to be an oversized fly. I looked up horseflies but the bug I found had widest eyes. What is it?
Signature: Audrey

Bot Fly

Bot Fly

Dear Audrey,
There is enough detail in your images for us to determine that this is a Bot Fly in the genus
Cuterebra, the Rodent Bot Flies, but we haven’t the necessary skills, and we suspect there is not enough image detail for even an expert to determine a species identification.  You can compare your image to this individual from BugGuide that also is identified only to the genus level.  According to BugGuide:  “Females typically deposit eggs in the burrows and “runs” of rodent or rabbit hosts. A warm body passing by the eggs causes them to hatch almost instantly and the larvae glom onto the host. The larvae are subcutaneous (under the skin) parasites of the host. Their presence is easily detected as a tumor-like bulge, often in the throat or neck or flanks of the host. The larvae breathe by everting the anal spiracles out a hole (so they are oriented head-down inside the host). They feed on the flesh of the host, but only rarely does the host die as a result.”

What's That Bug? does not endorse extermination

Subject: A botfly in the far North?
Location: Far North, Ont., Can.
September 15, 2013 9:23 am
I caught a mouse one night and found that there were four huge bumps on its back. I looked closer and saw what appeared to be botfly larvae in holes on each bump. I froze it and gave it to our local science teacher who dissected it with her class. Here’s a picture of what they dissected. Sure looks like a botfly to me!
I live in Fort Albany First Nation, Ontario, Canada, and I am surprised that there are botflys this far North! But is it really a botfly?
Signature: FAFN Resident

Rodent Bot Fly Larva removed from Dissected Mouse

Rodent Bot Fly Larva removed from Dissected Mouse

Dear FAFN Resident,
We concur that this is a Rodent Bot Fly Larva.  According to BugGuide Data, Bot Flies are found in Canada.

What's That Bug? does not endorse extermination

Subject: Two Larva Eat and Kill Mouse
Location: Mass USA
September 3, 2013 5:08 pm
I caught a mouse in my kitchen. I come to find I was able to because it was injured. I put it into a clear cage to show the kids. I come to find the mouse has a hole in its stomach and Two protruding round items imbedded inside. Which I thought were ticks. The mouse is almost dead anyways. So I decide to keep it in the container and wait to see what happens. I check the next day after work and find the bugs detached from the mouse. Each about a half inch long wiggling around. Not really moving in any direction but just wiggling. I also showed this to a friend who’s an exterminator and he says he’s never seen anything like it, also the mouse may be a rat. If that helps. I’ve always been into bugs and snakes, etc. I have never seen anything like this before. Should I be worried seeing as I caught the mouse in the house?
Signature: Matt

Bot Fly Larva emerges from Mouse

Bot Fly Larva emerges from Mouse

Dear Matt,
Bot Fly or Warble Fly Larvae in the family Oestridae are common endoparasites in mammals, especially rodents.  The adult Bot Fly resembles a bumble bee.  From what we have read, the larvae do not kill the host, so perhaps your mouse died of other causes, or perhaps in the case of small animals, the Bot Fly Larvae can do significant damage.  We will copy Bot Fly specialist Jeff Boettner to see if he can add any information.

Bot Fly Larvae

Bot Fly Larvae

What's That Bug? does not endorse extermination

Subject: Bot fly larva found in house!
Location: Cherokee County, NC
July 24, 2013 7:28 am
We found this fat little fellow slowly inching across the floor of our family room earlier this morning. Last night our cat decided to entertain herself by bringing in a dead mouse, so I think the little maggot likely came from the unfortunate rodent. It measured about an inch when scrunched up in the shape pictured, and a little longer when tying to move.
The mouse appeared to be a common house mouse, so I’m thinking it might be a Rodent bot fly, perhaps?
Signature: Jacob

Bot Fly Larva

Bot Fly Larva

Dear Jacob,
Your Bot Fly Larva photo is a welcome addition to our site.
  Your speculation that it came from the mouse your cat brought in is most likely correct.

What's That Bug? does not endorse extermination

Subject: Is this a Bumble Bee?
Location: Central New Hampshire
July 20, 2013 4:28 pm
Black and white markings, about the size of a Bumble Bee. Have never seen a bee
quite like this. It was very near a DogWood Tree in our yard.
Signature: Psquare

Bot Fly

Bot Fly

Dear Psquare,
It is easy to mistake this Bot Fly for a Bumble Bee.  Bot Flies are true flies and they are parasitic in the larval form, and according to BugGuide:  “The larvae are subcutaneous (under the skin) parasites of the host. Their presence is easily detected as a tumor-like bulge, often in the throat or neck or flanks of the host. The larvae breathe by everting the anal spiracles out a hole (so they are oriented head-down inside the host). They feed on the flesh of the host, but only rarely does the host die as a result.”  We are going to copy Jeff Boettner in our response in the hope that he can identify the species of Bot Fly you have photographed.

Hi Daniel and Psquare,
Your bot fly is a Cuterebra fontinella fontinella bot. This bot is a parasite of white footed mice, Peromyscus leucopus. Its a little hard to see the key features (a side view is helpful) but there are only a handful of bots in NH and this is the most common bot in your area. The other bots have either red eyes (rabbit bots) or more white or yellow on their backs. So I am confident of this ID. By the distance between the eyes, this one is a female.
Thanks for the post.
Jeff Boettner

What's That Bug? does not endorse extermination

Subject: Parasitic Larva
Location: Chihuahuan Desert, Far West Texas near the Rio Grande
April 19, 2013 4:01 pm
Hi there! This morning I set out to doctor what I thought was an infected thorn stuck in my dog’s side. Imagine my shock when instead of a thorn, I pulled out a wiggling larva! It didn’t look like a normal fly maggot to me, and a quick search of the internet pointed me to the Bot Fly. I’d really appreciate your expertise to clear up this baby bug’s identity.
Signature: Sara

Bot Fly Larva

Bot Fly Larva

Hi Sara,
We are really happy you identified your dog’s Bot Fly Larva, and even though they are allegedly not a threat to the health of the host, your dog is probably relieved to have had it removed.

What's That Bug? does not endorse extermination