Pachycondyla impressa

A fairly common species within its range and preferred habitats.

Identification
From Mackay and Mackay (2010): The large size of P. impressa would separate it from most of the other species of Pachycondyla. Pachycondyla impressa could be easily separated from other large species such as Pachycondyla commutata and Pachycondyla laevigata by the dull surfaces (P. commutata and P. laevigata are mostly shiny), from Pachycondyla crassinoda  by the lack of the two sharp lateral processes on the pygidium (which are present in P. crassinoda) and from Pachycondyla villosa and Pachycondyla striata by the relatively rounded pronotal shoulders (formed into distinct sharp carinae in P. villosa and P. striata). The lack of a metanotal suture in the smaller workers of P. impressa could cause confusion with the smaller Pachycondyla harpax (total length of worker less than 10 mm). It can be separated as the carina on the pronotal shoulder of P. harpax is relatively sharp, but not greatly raised from the surface (absent in P. impressa). Additionally the middle of the pygidium is concave in P. impressa, not rounded as in P. harpax. Some small isolated specimens are essentially impossible to separate into one species or the other. Pachycondyla impressa is superficially similar to the rare Colombian Pachycondyla fuscoatra; it can be easily separated by the depressed pygidium and the striae on the side of the pygidium, both of which are absent in P. fuscoatra. It is also slightly smaller and the posterior lateral edges of the petiole are rounded, not sharply marginate as in P. fuscoatra.

Pachycondyla impressa workers are nearly identical to those of Pachycondyla lattkei. It differs in that the dorsum of the gaster is dull and sculptured, not smooth and glossy as in P. lattkei. There are exceptions, especially in specimens from Ecuador, which have a smooth gaster, but are otherwise identical to P. impressa. The pygidium is strongly depressed in P. impressa, but rounded and not depressed in P. lattkei. The lobes on the metasternal process of P. impressa are often relatively close (usually less than 0.3 mm between the tips) and a pair of internal teeth is nearly always present and if the teeth are poorly developed, at least a swollen region is present, both of which are absent in P. lattkei.

The workers and females of Pachycondyla purpurascens from Costa Rica and Pachycondyla inca  from Perú and Bolivia are nearly identical to P. impressa, except the clypeuses are slightly longer and less emarginate along the medial border. The male of P. impressa is are also very similar to those of P. inca and P. striata. The relatively small ocelli, the large size and coarse rugae along the posterior lateral edge of the petiole would separate the males of P. impressa from most of the others. The concave anterior margin of clypeus will separate P. impressa from the very similar P. lattkei. The single examined male of P. impressa was not associated with workers, but a process of elimination and the similarity of this species with the closely related P. lattkei, are strong evidence that this male is a member of P. impressa. An unidentified male near P. impressa was collected in Quincemil (Cuzco), Peru (MCZC). It differs from the male of P. impressa in having rugae on the side of the petiole (similar to P. lattkei) and in having a wide petiole (width 1.4 mm). The anterior border of the clypeus is concave as in P. lattkei. Pachycondyla harpax variety irina is a smaller P. impressa, but the sides of the pronotum are nearly rounded and the pygidium is concave, indicating that it is actually P. impressa. Pachycondyla fuscoatra montana differs from the typical P. impressa in having a slightly more developed pronotal carina. Kempf (1961) synonymized P. fuscoatra var. andicola (which was not seen) and P. fuscoatra variety cearensis, which is actually a synonym of P. inca.

Pachycondyla fuscoatra transversa has transverse striae on the dorsum of the pygidium, which are usually lacking in P. impressa. There is considerable variation in this character and we follow Kempf (1961) in considering this to be a synonym of P. impressa.

Distribution
Central America through central South America, Trinidad. (Mackay and Mackay 2010)

Distribution based on Regional Taxon Lists
Neotropical Region: Bolivia, Brazil, Colombia, Costa Rica, Ecuador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Panama, Peru, Suriname, Trinidad and Tobago, Venezuela.

Habitat
This common species is found in a variety of habitats, ranging from lowland rain forest, at a pasture edge, dry tropical forest, the edge of second growth rain forest, cloud forest, thick wet cloud forest, low montane rain forest, upper montane cloud forest, tropical evergreen forest, a forest slope, montane hardwood forest, cloud forest, a roadside in a sunny spot, a cacao plantation, montane tropical forest, to a guano cave; at elevations ranging from 10 - 2350 meters. (Mackay and Mackay 2010)

Biology
From Mackay and Mackay (2010): Pachycondyla impressa nests in and under rotten logs and under stones. Brood was present in nests in July (Colombia) and August (Costa Rica). Females were collected in nests in January (Panamá) and April (Brasil). Dealate females have been collected in February and March (Costa Rica), April (Panamá), May (Panamá, Perú), June (Panamá), July (Perú) and August (Venezuela). Kempf (1961) mentions isolated females from Brasil were collected in March, May and October.

Individuals have been collected in intercept traps, pitfall traps and foraging on the ground. Workers were extracted from cacao leaf litter and other similar materials. Foragers are attracted to peanut butter baits (Kaspari and Weiser, 2000). One series was collected in the stomach of a Bufo toad. Workers are alert and fast. Sexuals are attracted to lights. They are parasitized by the head decapitating phorid fly Apocephalus (Brown and Feener, 1991).

Nomenclature

 *  impressa. Ponera (Pachycondyla) impressa Roger, 1861a: 6 (w.) COLOMBIA. Mackay & Mackay, 2010: 395 (q.m.). Combination in Pachycondyla: Roger, 1863b: 18. Senior synonym of andicola, montana, transversa: Kempf, 1961c: 195.
 * transversa. Pachycondyla fuscoatra r. transversa Emery, 1890a: 58 (w.) COSTA RICA. [Also described as new by Emery, 1890b: 42; Emery, 1894k: 48.] Forel, 1908b: 38 (q.). Raised to species: Dalla Torre, 1893: 35. Subspecies of fuscoatra: Forel, 1908b: 38. Junior synonym of impressa: Kempf, 1961c: 195.
 * montana. Pachycondyla fuscoatra var. montana Forel, 1912c: 39 (w.) COLOMBIA. Junior synonym of impressa: Kempf, 1961c: 195.
 * andicola. Pachycondyla fuscoatra var. andicola Santschi, 1913h: 34 (w.) ECUADOR. Junior synonym of impressa: Kempf, 1961c: 195.

Worker
From Mackay and Mackay (2010): The workers are usually large (total length about 11 mm) black ants with reddish brown appendages. Most surfaces are dull and punctate; the mandibles are relatively smooth and glossy. The eyes are relatively small (maximum diameter 0.5 mm) and separated from the anterior edge of the head (side view) by less than one diameter. The malar carina is not developed anterior to the eye. The pronotal shoulder is swollen but usually does not form a carina, the dorsum of the mesosoma is broadly convex and the metanotal suture is poorly marked or absent on the dorsal surface of the mesosoma. The propodeal spiracle is slit-shaped. The petiole is large and thick when viewed in profile, rectangular-shaped with the apex sometimes being slightly broader than the region near the base of the peduncle. The anterior face of the postpetiole is slightly concave and forms a relatively sharp angle with the dorsal surface. The metasternal process consists of two triangular lobes with small teeth on the interior surfaces. Erect hairs are moderately abundant, including on the malar area, the shaft of the scape, the dorsal and ventral surfaces of the head, the dorsum of the mesosoma, the legs (many hairs are suberect), the dorsum of the petiole and all surfaces of the gaster.

The mandibles are finely sculptured and moderately to strongly shining, the head and mesosoma are dull and punctate with some of the punctures in rows that appear as poorly defined striae, especially on the dorsum of the mesosoma and the mesopleuron. The petiole is roughly punctate; the gaster has scattered punctures and is moderately smooth and glossy.

Queen
From Mackay and Mackay (2010): The female is similar to the worker, but is somewhat larger (total length 16 mm). The remainder of the ant is nearly identical to that of the worker, except ocelli are present, the mesosoma is swollen and the metanotum is well developed.

The pilosity and sculpture are similar to those of the workers.

Male
From Mackay and Mackay (2010): (not associated with workers or females.) The male (undescribed) is a large (total length 15 mm) black specimen. The mandibles are tiny with well-developed depressions near the bases. The medial anterior margin of the clypeus is strongly concave, the surface of the clypeus is convex, but it does not overhang the anterior half when the head is seen from side. The head length is 1.80 mm, the head width is 1.84 mm. The eye is moderate in size (maximum diameter 0.83 mm) located less than one diameter from the lateral ocellus (oblique side view). The medial ocellus (diameter 0.15 mm) is located more than one diameter (distance of 0.24 mm) from the lateral ocellus (0.16 mm).

The pronotum is barely swollen at the shoulder. The Mayrian furrows are well developed as are the parapsidal sutures. The scutellum is swollen and rounded when viewed from side. The spiracle is slit-shaped. The petiole is wide when viewed in profile with sloping (not parallel) anterior and posterior faces, which narrow dorsally and form a broadly rounded dorsal face. The subpetiolar process is poorly developed and consists of a rounded lobe anteriorly with the remainder of the process gradually diminishing in width posteriorly. The anterior face of the postpetiole is broadly rounded; the postpetiolar process is not developed. The pygidium is not depressed or concave as in the worker and female. Erect hairs are mostly short (0.1 - 0.35 mm) and are present on the clypeus, dorsal surface of the head (ventral surface cannot be seen), dorsum of the mesosoma, dorsum of the petiole, ventral surface of the petiole and all surfaces of the gaster. The hairs on the legs are mostly appressed, especially on the tibiae, a few hairs on the coxae are erect and suberect. Appressed golden pubescence is scattered on all surfaces.

The head is very finely punctate and weakly shining, the mesosoma is similar, but some of the surfaces, especially the mesopleuron, are moderately shiny. The side of the propodeum and the side of the petiole have poorly developed rugae with well-developed rugae near the posterior lateral edges and on the apex. The gaster is finely punctate and moderately shining.

Type Material
Lectotype worker and 2 paralectotype workers here designated, ; lectotype worker, 1 paralectotype worker labeled, others labeled as syntypes from Suerre and El Aragua, Costa Rica and Río Frio, Colombia, ; lectotype worker and 1 paralectotype worker seen,, 3 syntypes workers, , 6 worker syntypes (Mackay and Mackay 2010)

Type Locality Information
Colombia; Costa Rica, Alajuela, Juan Viñas; Dalla Torre; Colombia, Sierra Nevada de Santa Marta, San Antonio; Ecuador, Santo Domingo de los Colorados; Guatemala, Quirigua (Mackay and Mackay 2010) (Mackay and Mackay 2010)

Etymology
The name of this species is from the Latin word impressio, meaning a pressing into, referring to the impressed pygidium. (Mackay and Mackay 2010)

Additional References

 * Brown, B. V. and D. Feener. 1991. Behavior and host location cues of Apocephalus paraponerae (Diptera, Phoridae), a parasitoid of the giant tropical ant, Paraponera clavata (Hymenoptera: Formicidae). Biotropica 23:182-187.


 * Kaspari, M. and M. Weiser. 2000. Ant activity along moisture gradients in a Neotropical forest. Biotropica 32:703-711.