Bug FAQSouth American grooved ant
Gnamptogenys triangularis · Order: Hymenoptera · Family: Formicidae
It lives in forest habitats throughout its native range from Buenos Aires, Argentina up to Costa Rica and preys mainly on millipedes. Females are slightly larger than workers, measuring about 5.5 mm in length.
Source: Wikipedia
How to recognize it
The ant is black with more reddish legs and has deep longitudinal grooves on the head, mesosoma and gaster.
Source: Wikipedia
Size
Females are about 5.5 mm long, slightly larger than the workers.
Source: Wikipedia
Is it a pest in the house?
There are no documented impacts of this ant and it is unlikely to become a major pest.
Source: Wikipedia
Where it lives
It inhabits forests in both its native and introduced areas.
Source: Wikipedia
Where it comes from
It is native to forests of South and Central America, from Buenos Aires, Argentina north to Costa Rica.
Source: Wikipedia
Where it is found in the US
Recorded in 6 of 51 states and DC. Most records: Mississippi, Florida, Alabama, Texas, Georgia, South Carolina.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: introduced in United States. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
What does Gnamptogenys triangularis look like?
It is a relatively large black ant with reddish legs and deep grooves on its head and first gastral segment.
Source: Wikipedia
Where is Gnamptogenys triangularis found?
It is native to forested areas from Buenos Aires, Argentina up to Costa Rica in South and Central America.
Source: Wikipedia
What does Gnamptogenys triangularis eat?
It preys on millipedes and is considered a millipede specialist.
Source: Wikipedia
Is Gnamptogenys triangularis a household pest?
There are no documented impacts and it is unlikely to become a major pest.
Source: Wikipedia
Same family (Formicidae)
Eastern Black Carpenter AntCamponotus pennsylvanicusCan bite
Red Imported Fire AntSolenopsis invictaCan sting
American Winter AntPrenolepis imparis
Argentine AntLinepithema humileNuisance, not dangerous
Immigrant Pavement AntTetramorium immigransCan sting
Odorous House AntTapinoma sessileCan damage your homeSources
- Wikipedia: https://en.wikipedia.org/wiki/Poneracantha_triangularis
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-28 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-28.