Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Southern Mexico to mountains of Peru and northeast Brazil. Kempf (1972) lists Costa Rica, Colombia, Ecuador, Venezuela, Peru, Bolivia, Trinidad, Guianas, Brazil (AM, PA, CE, GB, RJ, SP). Costa Rica: Atlantic lowland wet forest to 800m; southern Pacific lowland wet forest to 1200m at Wilson Botanical Gardens near San Vito.
Mesosomal dorsum with erect hairs; opening of propodeal spiracle viewed perpendicularly slit-shaped, more than twice as long as wide; mandible with approximately 9 teeth; in side view, dorsal outline of mesosoma forms a continuous convexity including mesonotum, metanotum and propodeal dorsum; propodeal groove obsolete or nearly so, and not strongly impressed; cheeks without a distinct carina between lateral clypeal wing and eye margin; stridulatory file absent; arolia absent; head width greater than 2.0mm; mesosoma greater than 3.6mm long; dorsolateral margin of pronotum uniformly punctate, rounded; clypeus narrow front to back, with deep median notch that extends almost to anterior margins of frontal lobes.
Similar species: harpax is smaller, and usually has a dorsolateral carina on the pronotum; purpurascens has a deeper (front to back) clypeus.
This species is relatively rare, compared to the similar and much more abundant P. harpax. Foragers occur on the forest floor, and are never arboreal.
I have observed one nest of impressa. In Corcovado National Park, I put dead tabanids on the ground in an area with scattered impressa workers. One picked up a tabanid and I tried to follow it, but it was easily disturbed, and it would constantly hide motionless under leaves. I eventually found a nest entrance in the center of a mud clump. The nest went horizontally back into a clay bank, a short distance to a gallery about 2cm broad and 1cm high.
Ponera (Pachycondyla) impressa Roger 1861:6. Syntype worker: Colombia.
The transversa problem:
Pachycondyla fuscoatra r. transversa Emery 1890:58. Lectotype worker: Juan Vi–as [MCSN] (examined). Synonymized under P. impressa by Kempf 1961:195.
Emery included specimens from Alajuela and Juan Vi–as in his original description of transversa, and he later reidentified the Juan Vi–as specimens as Forel's purpurascens (Emery 1901, 1911). During a visit to the Emery collection in Genoa in 1990 I found no material clearly marked as the type of transversa, but there was a queen labeled "Alajuela" under transversa and two workers labeled "Juan Vinas" under purpurascens. I assumed these specimens were the syntypes. The queen matched what I consider impressa and the workers were purpurascens. Mackay and Mackay (2010) unfortunately made one of the Juan Vi–as workers the lectotype of transversa, and then incorrectly left transversa synonymized under impressa. Given this lectotype designation, purpurascens will have to become a junior synonym of transversa.
Bolton, B. 1995. A New General Catalogue of the Ants of the World. Harvard University Press, Cambridge, Mass.
Emery, C. 1890. Studi sulle formiche della fauna neotropica. I-V. Bullettino della Societa Entomologica Italiana 22:38-80.
Emery, C. 1901. Notes sur les sous-familles des Dorylines et Ponerines (Famille des Formicides). Annales de la Societe Entomologique de Belgique 45:32-54.
Emery, C. 1911. Hymenoptera. Fam. Formicidae. Subfam. Ponerinae. Genera Insectorum 1181-125.
Kempf, W. W. 1961. As formigas do genero Pachycondyla Fr. Smith no Brasil (Hymenoptera: Formicidae). Revta Bras. Entomol. 10:189-204.
Kempf, W. W. 1972. Catalogo abreviado das formigas da Regiao Neotropical. Studia Entomol. 15:3-344.
Mackay, W. P., and E. E. Mackay 2010. The Systematics and Biology of the New World Ants of the Genus Pachycondyla (Hymenoptera: Formicidae). Edwin Mellon Press, Lewiston.
Roger, J. 1861. Die Ponera-artigen Ameisen (Schluss). Berl. Entomol. Z. 5:1-54.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.firstname.lastname@example.org
Go to Ants of Costa Rica Homepage