Tabanus atratus
In 3 days ~10% in a week ~20%
Tabanus is a genus of biting horseflies of the family Tabanidae. Females have scissor-like mouthparts that are able to penetrate the skin of livestock animals. The horsefly can then extract and ingest the animal's blood. Horseflies of this genus are known to be potential vectors of anthrax, worms and trypanosomes. Some species, such as Tabanus bovinus, prefer bovine animals and are less harmful to humans. The genus contains hundreds of species and many species groups. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Padre Island National Seashore | 🇺🇸 United States | |
| 2 | Merritt Island National Wildlife Refuge | 🇺🇸 United States | |
| 3 | Big Cypress National Preserve | 🇺🇸 United States | |
| 4 | Everglades National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Baltimore | 🇺🇸 United States | |
| 2 | Minneapolis [Saint Paul] | 🇺🇸 United States | |
| 3 | Houston | 🇺🇸 United States | |
| 4 | Washington | 🇺🇸 United States | |
| 5 | Montreal | 🇨🇦 Canada | |
| 6 | Austin | 🇺🇸 United States | |
| 7 | Dallas | 🇺🇸 United States | |
| 8 | Chicago | 🇺🇸 United States | |
| 9 | Toronto | 🇨🇦 Canada | |
| 10 | Philadelphia | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Black Horse Fly sighting in Chicago on a given day, based on 22 verified sightings from GBIF citizen-science data. It is the 396th most-seen of the 978 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
August
In that month about 10% of wildlife watchers report a Black Horse Fly in Chicago on a given day, against under 5% in September to July, the lowest months.
Between 9 am and noon
Across all the parks we cover, that three-hour window holds the most Black Horse Fly sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Among the best
Of the 13 cities where we can rate Black Horse Fly sightings, Chicago ranks 8th at under 5%, level with the leaders once rounded. The best odds are in Baltimore (United States, under 5%), Minneapolis [Saint Paul] (United States, under 5%) and Houston (United States, under 5%).
Same order: Diptera
The closest relatives of the Black Horse Fly that you can see in Chicago (order Diptera, Flies) are Margined Calligrapher (about 10%), Narrow-Headed Marsh Fly (about 10%) and Common Picture-Winged Fly (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Black Horse Fly is recorded against all the insects logged in Chicago (22 verified sightings), 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.
