Cuterebra fontinella
In 3 days ~10% in a week ~30%
Cuterebra fontinella, the mouse bot fly, is a species of New World skin bot fly in the family Oestridae. C. fontinella is typically around 1 cm (0.39 in) in length with a black and yellow color pattern. C. fontinella develops by parasitizing nutrients from its host, typically the white-footed mouse. C. fontinella has even been known to parasitize humans in rare cases. Individuals parasitized by C. fontinella will develop a large bump on the skin that is indicative of parasitization.
The genus name Cuterebra is a blend of the Latin words cutis : skin and terebra : borer with apparent shortening of expected Cutiterebra to Cuterebra. C. fontinella is found all around North America, including in most of the continental United States, southern Canada, and northern Mexico. The prevalence of C. fontinella is dependent upon temperature. Colder regions will not be as densely populated as the warmer ones.
C. fontinella inhabits deciduous forests of North America. C. fontinella prefer territories near running water and with low-elevation vegetation. These flies are found in the highest density near the edges of their habitats. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Olympic National Park | 🇺🇸 United States |
More parks will be added in future updates.
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Toronto | 🇨🇦 Canada |
Rare
Under 5% of wildlife watchers report a Mouse Bot Fly sighting in Olympic National Park on a given day, based on 7 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 150th most-seen of the 207 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
August
In that month about 10% of wildlife watchers report a Mouse Bot Fly in Olympic National Park on a given day, against under 5% in September to July, the lowest months. That is one of Olympic National Park's driest months, with about 45 mm of rain against 370 mm in November.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Mouse Bot Fly sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
Only Olympic National Park, in our data
Olympic National Park is the only park on Wallace's Line with enough records to rate Mouse Bot Fly sightings: under 5% of wildlife watchers there report one on a given day.
Same order: Diptera
The closest relatives of the Mouse Bot Fly that you can see in Olympic National Park (order Diptera, Flies) are Common Drone Fly (about 10%), Western Pond Fly (about 10%) and Black-Margined Flower Fly (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Mouse Bot Fly is recorded against all the insects logged in Olympic National Park (7 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
