rodent bot flies

Cuterebra is a genus of large, parasitic flies. They occur throughout North America, Mexico, and Central America, and are also found in South America. There are 78 Cuterebra species worldwide, 26 species in North America north of Mexico, and at least 6 species in Minnesota. They attack rodents, rabbits, and hares. Females lay their eggs in burrows and on “runs”. The eggs hatch almost instantly when they sense a passing warm body and the larvae attach themselves to the body. The larvae bore under the skin and feed on the flesh of the host. They produce boil-like swellings. Several larva may inhabit a single host.

Larvae are very common but adults are rarely seen. Adults do not feed. They fly early in the day, and are usually found in the proximity of their hosts, often on hilltops.

Cuterebra are large, robust, hairy, bee-like flies. They are usually identified by the species in which the larva is found. Adults are up to 13⁄16″ (30 mm) in length. The antennae have three segments. On the second segment there is a longitudinal, line-like groove (suture). The mouth opening is very small. The exoskeletal plate between the abdomen and the thorax (scutellum) is very short. The area just behind the scutellum (postscutellum) is well developed. On the wing the terminal cell (R₅) of the radial sector (Rs) is closed or narrowed toward the end (distally).

Sources

7, 24, 27, 29, 30, 82.

My cat caught a mouse and I found this larva.

I found something that I need help identifying.

Rabbits have completely overrun my property after the red fox population vacated when I brought livestock dogs home. I have been trying to control their numbers as they create havoc on my fruit trees and crops.

This evening I shot what appeared to be a sick rabbit. When I looked at it there was an area near where I shot that was a hole but the skin surrounding it was dry and hard so I know it was not from me. When I looked closer there was something moving inside of it and was large enough to see the fur moving when not touching the animal. When examining a large amount of blood and puss came out from the injury.

I've attached some screenshots. The inside of the rabbits ears were white which may indicate anemia or other illness though I could be wrong about this.

The parasite inside was hard/crusty, black, and has two orifices towards the surface. On the underside of the neck there was another opening about the same size as the other. The fur near the neck was gone and the skin was discolored a brownish color and scaly.

It is something I have never seen before, hopefully you have some insights or may be able to direct me to someone who may know. I have an email out to the UofM for their insights as well.

I'm hoping it isnt anything I need to worry about regarding my farm animals or my kids and I walking barefoot in the yard.

Cuterebra, bot fly, sitting on Ratibida pinnata, gray headed coneflower

The dust on it is from the bird seed container I used to save it from the lawn mower.

Location: Huntersville, Wadena Co.

My cat caught a mouse and I found this larva.

Location: Sherburne County, MN

I found something that I need help identifying.

Rabbits have completely overrun my property after the red fox population vacated when I brought livestock dogs home. I have been trying to control their numbers as they create havoc on my fruit trees and crops.

This evening I shot what appeared to be a sick rabbit. When I looked at it there was an area near where I shot that was a hole but the skin surrounding it was dry and hard so I know it was not from me. When I looked closer there was something moving inside of it and was large enough to see the fur moving when not touching the animal. When examining a large amount of blood and puss came out from the injury.

I've attached some screenshots. The inside of the rabbits ears were white which may indicate anemia or other illness though I could be wrong about this.

The parasite inside was hard/crusty, black, and has two orifices towards the surface. On the underside of the neck there was another opening about the same size as the other. The fur near the neck was gone and the skin was discolored a brownish color and scaly.

It is something I have never seen before, hopefully you have some insights or may be able to direct me to someone who may know. I have an email out to the UofM for their insights as well.

I'm hoping it isnt anything I need to worry about regarding my farm animals or my kids and I walking barefoot in the yard.

This a rodent bot fly in the genus Cuterebra. Of the six Cuterebra species known to occur in Minnesota, only two, Cuterebra buccata and Cuterebra abdominalis use eastern cottontail (Sylvilagus floridanus) as a host. Cuterebra buccata has been recorded in all states surrounding Minnesota but not in Minnesota itself. One source (Cedar Creek Ecosystem Science Reserve) shows the species present in Minnesota, but it has no records. There are several records of Cuterebra abdominalis in Minnesota. Based on this, the parasite in your photo is most likely Cuterebra abdominalis, but Cuterebra buccata cannot be ruled out. For this reason, your photo will be placed on the Cuterebra genus page.

As far as the possibility of your kids becoming infected, this is from Oregon State University Extension Service:

It is not impossible for humans to get infected, but it is quite rare. To become infected, the fly (adult form) would have had to lay eggs in or near a wound.

Location: Barnes Prairie Remnant, Racine Co., WI

Cuterebra, bot fly, sitting on Ratibida pinnata, gray headed coneflower

Location: Burnsville, MN

Caught a mouse in a trap in our crawl space and the brown larva thing was underneath the mouse.

Location: New Hope, Minnesota

…tons coming out odiferous a rabbits neck in a yard

Location: Red Wing, MN

My cat caught a mouse this morning, the larvae came out of the dead mouse.

Location: North St. Paul MN

Seen a mouse come out of my garage had my nephew get the bb gun to kill it. He went to grab it and we thought it was a baby coming out of its genital area I had him pull it out because I was curious it didn't look like a baby. Googled it and this it what came up. It had a total of 3 of these things in there. The first one was the biggest. The one pictured was the medium sized one.

Location: Coon Rapids, MN

scooped it out of my swimming pool, still alive. Googled it, went back outside and killed it.

Location: White Bear Lake, Minnesota

Took my cat to the vet this morning. Doctor removed what he said was a bot fly larva.

Location: Scott County

The dust on it is from the bird seed container I used to save it from the lawn mower.