Diachlorus ferrugatus
In 3 days ~10% in a week ~20%
Diachlorus ferrugatus, commonly known as the yellow fly or yellow fly of the dismal swamp in the United States or doctor fly in Belize, is a species of highly aggressive biting horse-fly of the family Tabanidae native to North and Central America to Costa Rica.
The yellow fly was described as Chrysops ferrugatus by Johan Christian Fabricius in 1805. Adult yellow flies are around 1 centimetre (0.39 in) long with yellow bodies, mid-legs, and hind-legs, and black fore-legs. The eyes are blue-green with purple bands. They fly with little sound, and the first sign of their presence noticed by humans is usually their bite.
The larvae are thin white grubs with fine yellow fur, each segment having three pairs of pseudopodia. The yellow fly ranges from the southeastern United States, where it is found from New Jersey to Texas, to Costa Rica. It is most common near bodies of water, along with trees nearby to hide in. Spanish moss (Tillandsia usneoides) is a popular hiding spot.
It is notorious for its propensity to inflict painful bites on people, having been described as the most aggressive fly species in... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Sian Ka'an Biosphere Reserve | 🇲🇽 Mexico | |
| 2 | Big Cypress National Preserve | 🇺🇸 United States | |
| 3 | Everglades National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Orlando | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Yellow Fly Of The Dismal Swamp sighting in Orlando on a given day, based on 8 verified sightings from GBIF citizen-science data. It is the 191st most-seen of the 294 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.
May–June and August
In those months about 10% of wildlife watchers report a Yellow Fly Of The Dismal Swamp in Orlando on a given day, against under 5% in July and September–April, the lowest months. Those are among Orlando's wettest months, with about 170 mm of rain a month against 50 mm in November.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Yellow Fly Of The Dismal Swamp sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Only Orlando, in our data
Orlando is the only city on Wallace's Line with enough records to rate Yellow Fly Of The Dismal Swamp sightings: under 5% of wildlife watchers there report one on a given day.
Same order: Diptera
The closest relatives of the Yellow Fly Of The Dismal Swamp that you can see in Orlando (order Diptera, Flies) are Common Lovebug (about 10%), Condylostylus mundus (about 10%) and Florida Calligrapher (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Yellow Fly Of The Dismal Swamp is recorded against all the insects logged in Orlando (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.
