Pest profile

Robust Crazy Ant

Nylanderia bourbonica · Hymenoptera: Formicidae[2]

The robust crazy ant is a minor nuisance in outdoor eating areas and rarely enters buildings in large numbers.[1]

Robust crazy ant worker, a glossy dark brown ant covered in long erect hairs, on a white background
Robust crazy ant worker, a glossy dark brown ant covered in long erect hairs, on a white background. (c) Mike Bowie, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Workers are 2.1 to 3.2 mm, dark brown to almost black and glossy, with abundant long black hairs.[1]
  • It has the largest workers of the dark Nylanderia crazy ants in the U.S.[1]

Look-alikes

Look-alikeHow to tell them apart
Tawny crazy antAnother non-native Nylanderia crazy ant in Florida.[1]

Where it lives

Introduced from the Old World tropics, it's recorded through the southern two-thirds of Florida's peninsula, with specimens dating to 1924.[1]

US map: public records from 5 states since 1990 (GBIF).

Biology and life cycle

Colonies eat other insects plus sugary honeydew from aphids and mealybugs.[1]

Workers find food fast but can't defend it from red imported fire ants.[1]

Damage and signs

  • It's been ranked the eighth most abundant urban pest ant in peninsular Florida.[1]

Health risk

UF/IFAS describes it as a minor nuisance and mentions no health risk.[1]

Control

Keep them out

Seal possible entryways, especially around doors and windows.[1]

Sanitation

Control excess moisture, since it lives in damp areas.[1]

Pesticides

Liquid ant baits attract workers and should be effective; broad spraying shouldn't be needed.[1]

Common questions

Do robust crazy ants come inside?
Rarely in large numbers, probably only for shelter in cold weather.[1]
What's the best way to control them?
Liquid ant baits plus sealing entry points; broad spraying shouldn't be needed.[1]

Sources

  1. University of Florida IFAS Extension (Featured Creatures), “Robust Crazy Ant, Nylanderia bourbonica (EENY-685).” edis.ifas.ufl.edu/publication/IN1183 (accessed 2026-10-06)
  2. iNaturalist, “Nylanderia bourbonica taxon page (order and family).” www.inaturalist.org/taxa/625860 (accessed 2026-10-06)

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