Pest profile

Yellow Fly

Diachlorus ferrugatus · Diptera: Tabanidae[2]

The yellow fly is a fierce daytime biter whose bites are painful and often cause large, itchy swellings.[1]

Yellow fly, a yellow-bodied fly with green banded eyes and dark-tipped wings, on weathered wood
Yellow fly, a yellow-bodied fly with green banded eyes and dark-tipped wings, on weathered wood. (c) Philip Curley, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adults are mostly yellow, about 3/8 inch long, with clear wings carrying a brown patch at the tip.[1]
  • Live flies have brilliant blue-green eyes crossed by two purple bands.[1]

Look-alikes

Look-alikeHow to tell them apart
Deer fliesDeer flies have a brown band across the middle of the wing; the yellow fly's patch is at the wing tip.[1]
Horse fliesYellow flies belong to the same family, Tabanidae.[1]

Where it lives

It's found in the southeastern U.S. from New Jersey to Texas, plus the Bahamas and Mexico to Costa Rica.[1]

US map: public records from 13 states since 1990 (GBIF).

Biology and life cycle

Larvae live in water-soaked root mats in deep shade; the full life cycle usually takes about a year.[1]

In Florida adults fly March to November, peaking April through June.[1]

Damage and signs

  • It bites most in late afternoon and on cloudy days, stays near forests and is one of the few tabanids that bites indoors.[1]

Health risk

Bites are painful and swell; people sensitive to bites should avoid exposure to prevent serious reactions.[1]

Control

Prevention

DEET is the most effective repellent; gloves and head nets are the only sure protection.[1]

Traps and physical control

Traps sometimes help in small areas such as yards, campsites and pools.[1]

Common questions

What is the yellow fly that bites so hard in Florida?
Usually Diachlorus ferrugatus, the true yellow fly, a fierce daytime biter.[1]
Does repellent work on yellow flies?
Moderately; DEET works best, but gloves and head nets are the only sure protection.[1]

Sources

  1. University of Florida IFAS Extension (Featured Creatures), “Yellow Fly, Diachlorus ferrugatus (EENY-320).” edis.ifas.ufl.edu/publication/IN595 (accessed 2026-10-06)
  2. iNaturalist, “Diachlorus ferrugatus taxon page (order and family).” www.inaturalist.org/taxa/258381 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.