Poneracantha triangularis

A millipede feeder that is found in humid forests. The USA record (Deyrup, et. al. 1989:93) is undoubtedly a recent introduction and they have apparently found prey in the local species of millipedes, as they are well established. (Lattke 1995)

Identification
A member of the rastrata complex (in the rastrata subgroup of the rastrata species group). Promesonotal suture weakly impressed; node dorsum with transverse costulae and subquadrate costulae and subquadrate subpetiolar process; first gastric sternum with transverse costulae; metacoxal tooth long and thin. Piceous body. (Lattke 1995)

Distribution
Introduced into Alabama and Florida (Dade and Escambia counties) from Central or South America. It is not as yet common there, but seems well established. First published Florida record: Deyrup et al. 1989; earlier specimens: 1985. (Deyrup, Davis & Cover, 2000.)

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Argentina, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, French Guiana, Peru, Uruguay.



Biology
This species was studied in Venezuela by Lattke (1990). He found nests in fallen logs and branches, inhabited by 80-120 individuals. In the four nests examined he found only the remains of millipedes, in the form of disarticulated segmental rings, surrounding the area of the nest. Larvae were found with their heads thrust into the body of a dead millipede. Many millipedes secrete powerful defensive secretions, including cyanide. Lattke found that both adults and larvae of G. triangularis are resistant to cyanide, surviving for three hours in a potassium cyanide killing jar that killed other ants in less than five minutes. Even the G. triangularis were dead in twelve hours.

A colony from Homestead, Florida, had many millipede fragments in the nest (Gary Umphrey 1987, pers. comm.; Deyrup, Davis & Cover, 2000).

Nomenclature

 *  triangularis. Ectatomma (Gnamptogenys) triangulare Mayr, 1887: 544 (q.) URUGUAY. Emery, 1906c: 113 (w.). Combination in E. (Parectatomma): Emery, 1911d: 44; in Gnamptogenys: Brown, 1958g: 230. Senior synonym of richteri: Brown, 1958g: 230; of aculeaticoxae: Lattke, 1995: 190.
 * richteri. Ectatomma (Parectatomma) triangulare r. richteri Forel, 1913l: 203 (w.) ARGENTINA. Forel, 1914d: 265 (q.). Junior synonym of triangularis: Brown, 1958g: 230.
 * aculeaticoxae. Ectatomma (Parectatomma) aculeaticoxae Santschi, 1921g: 82 (w.m.) FRENCH GUIANA. Wheeler, G.C. & Wheeler, J. 1971b: 1201 (l.). Combination in E. (Poneracantha): Santschi, 1929h: 476; in Gnamptogenys: Brown, 1958g: 227. Junior synonym of triangularis: Lattke, 1995: 190. See also: Lattke, 1990b: 5.

Lattke (1995) - The number of transverse costulae on the petiolar dorsum can vary from 8 to 14, and those on the pronotum from 13 to 23. Specimens from Argentina tend to have a higher count but there is no gap separating the values. The length of the coxal teeth is variable and bears no relation to the number of petiolar costulae. Propodeal teeth also show variation form a low mound to the usual low, sharp teeth. Occasional specimens can have up to 4 transverse costulae on the anterior pronotal face, and rarely longitudinal costulae on the petiolar node. Other traits used by Santschi to separate Gnamptogenys aculeaticoxae, such as degree of impression of the promesonotal suture, gastric constriction and gauge of hairs, length vs. width of petiolar node and the mandibular costulation all show continuous variation that is best described as infraspecific.