Tabanus sudeticus
In 3 days ~10% in a week ~20%
Tabanus sudeticus, also known as the dark giant horsefly, is a species of biting horse fly. It is the heaviest fly in Europe. The dark giant horsefly's length is around 20-25 millimeters. They have uniform dark brown eyes. Diagnostic characters include:-Upper facets of eyes distinctly larger than lower facets, and sharply delineated from them. Subcallus entirely dull and tomented, (it may have brown (areas); venter of abdomen with each segment black basally, and in a rounded median extension; black species, with yellow abdominal triangles, but little or no lateral reddish colour. Parafacials with abundant black hairs.
Dark giant horseflies are a common species to be found buzzing around cows and horses. They usually only suck blood from horses and cows, avoiding humans. They fly with a very loud buzzing. Tabanus sudeticus is found in many countries of Western Europe. It has a marked northern and western distribution; being found as far north as Southern Norway and the Western Isles of Scotland, and with an occasional record from Belarus. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 2 | Cairngorms National Park | 🇬🇧 United Kingdom |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Vienna | 🇦🇹 Austria |
Rare
Under 5% of wildlife watchers report a Dark Giant Horse Fly sighting in Vienna on a given day, based on 8 verified sightings from GBIF citizen-science data. It is the 1028th most-seen of the 1406 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.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Dark Giant Horse Fly in Vienna on a given day, so our monthly data shows no clear season.
Between 2 and 5 pm
Across all the parks we cover, that three-hour window holds the most Dark Giant Horse Fly sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
Only Vienna, in our data
Vienna is the only city on Wallace's Line with enough records to rate Dark Giant Horse Fly sightings: under 5% of wildlife watchers there report one on a given day.
Same order: Diptera
The closest relatives of the Dark Giant Horse Fly that you can see in Vienna (order Diptera, Flies) are Marmalade Hover Fly (about 20%), Hornet Mimic Hover Fly (about 10%) and Common Drone Fly (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Dark Giant Horse Fly is recorded against all the insects logged in Vienna (8 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.
