Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Pachycondyla unidentata appears to be a species complex in Costa Rica, with possibly 4 species (see discussion below). The above images are of unidentata s.s.. See below for images of other species.
Range
Southern Mexico south through Amazonia. Costa Rica: Atlantic and Pacific slopes, wet and dry forests, sea level to at least 1200m in places.
Identification
Mandible with with more than ten teeth; mesosomal dorsum setose; 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; a distinct carina runs from the lateral wing of the clypeus near the mandibular insertion to or nearly to the anteromesal quarter of the margin around the eye; propodeal spiracle slit-shaped; acrotergite of second gastral tergum (when exposed) with a distinctly differentiated median stridulatory file with bands of rainbow colors; arolia present; petiolar node as seen from the side with front face rising abruptly to an angular summit at or near the front, from which it descends behind through a broad curve; posterior face of petiolar node densely and finely punctulate, not striate; clypeus with projecting anteromedian tooth.
If I maximally split species in Costa Rica, I find the following:
unidentata s.s.: sides of head above and behind compound eyes smooth, microreticulate, differing from dense and fine punctation of face (figure); all coxae clear yellow orange, rest of leg gradually darkening distally (figure); sides of propodeum with a few rugulae posteroventrally to metanotal spiracle, but dorsolateral face of propodeum smooth and shining (figure).
JTL-008: sides of head above and behind eyes densely punctate, similar to sculpture on face (figure); coxae and legs brown (figure); sides of propodeum with more extensive rugulae between metathoracic spiracle and propodeal spiracle, but rugulae not extending very far onto dorsolateral face of propodeum (figure); dorsolateral face of propodeum punctate, not shiny. Standard views: lateral view (reduced, original), face view (reduced, original).
JTL-009: head sculpture and propodeal sculpture identical to JTL-008; coxae and legs clear orange (figure).
JTL-010: head sculpture same as unidentata s.s. (figure); front coxae dark brown with variable stripe of orange at femoral insertion, middle and hind coxae and rest of legs clear orange (figure); sides of propodeum with extensive rugulae between metathoracic spiracle and propodeal spiracle, rugulae extend up over much of dorsolateral face of propodeum (figure).
Natural History
unidentata s.s.: This species is a very common ant in most Costa Rican forests, occurring in the canopy and low arboreal stratum. It is an opportunistic cavity nester, most often using dead branches and stems. It may occasionally be found in Cecropia saplings, and the abandoned carton nests of other ant species. Nests are small, often containing fewer than 10 workers. I once collected two dealate queens together in a small rotten stick, suggesting that pleometrotic founding may occur. The larvae are subject to predation by syrphid flies. The following two accounts are of syrphids found in unidentata nests:
Corcovado National Park, Sirena; 22 December 1981. Dana Meyer found a colony in a piece of rotten stick, hanging vertically at 1m height, outside dia. 9mm, inside 6mm. There were 12 ants total in the nest, including the single queen, 8 pupae, and 8 large larvae. Some may have been lost when the nest was first broken open. Two of the pupae were parasitized. There were fly puparia inside cocoons that had been neatly cut to allow for the greater width of the puparia, making a chinese lantern effect. The cuticle of the puparium was translucent, the organs visible inside. There was a produced, oval callosity on the side with a longitudinal slit in the center of the callosity. A darkly pigmented nipple was on one end. Two parasitoids were isolated from the ants. On 8 January one fly eclosed. Its wings did not expand properly. The puparium opened circumcissally just above the callosity on the ventral side. I put the remaining puparium back in with the ant colony, and the ants immediately picked it up and carried it back into the nest, where they placed it with the rest of the cocoons. They then returned and picked up the naked, empty puparium of the first fly (with much difficulty). They licked and fondled the empty skin for much longer than they licked the first, entire puparium. Finally they put the empty puparium with the cocoons. On 10 January I found the second fly dead outside the ant nest. Its wings had been clipped off, by the ants I presume.
Near Monteverde, 28 July 1984. Nesting in center of suspended rotten stick. The nest contained 4 or 5 parasitized pupae. The cocoons were split down the sides to accomodate the globose fly puparia, creating a chinese lantern effect. I kept four pupae alive in the lab, attempting to rear adults. I removed the surrounding ant cocoon from one of the pupae, and left the cocoons on the remaining three. An adult fly emerged from the naked pupa several days later, but its wings never unfolded properly. I waited another four days, and then observed that the remaining three were dead. They were pharate adults, and the pupal skins had split, but they were trapped inside by the ant cocoons. Thus, the flies must require the presence of the adult ants to remove the cocoon.
JTL-008: This species is very common in the canopy of mature forest at La Selva Biological Station, where it has been collected in canopy fogging samples from at least 5 different trees, and as strays in recent treefalls. I have two other collections from other localities: (1) a worker from a canopy tree, at 500m elevation in Braulio Carrillo National Park; and (2) workers from a recent treefall, Maritza Biological Station in the Guanacaste Conservation Area.
JTL-009: This species I know from one specimen; a worker from a canopy tree at Sirena, in Corcovado National Park.
JTL-010: This species I know from two collections in Costa Rica: (1) nesting in an internode of a Cecropia insignis sapling, at Casa Plastico near Rara Avis; and (2) a stray worker from Hitoy Cerere Biological Reserve. I also have workers collected by Phil Ward (PSW#11398) from a roadside Cecropia in Ecuador, and they are essentially identical to the Costa Rican collections!
Type Data
Pachycondyla unidentata Mayr 1862:720. Syntype worker, queen: Brazil, Amazonia.
Taxonomic Notes
Pachycondyla unidentata is a species complex that has accumulated 7 available names, as follows:
eburneipes: Brazil
laevinodis: Peru
maya: Guatemala
rugatula: Argentina
rugosula: Peru
trinidadensis: Trinidad
unidentata: Brazil
All but rugatula have been synonymized under unidentata (Brown 1957). If the species delimited in Costa Rica continue to be supported, and if they have geographic ranges that extend well beyond Costa Rica, some of the names in the species complex may be resurrected, and may apply to one or more of the Costa Rican species. I have used the name unidentata for the common secondgrowth species, on the presumption that a widespread weedy species might have been the first species in the complex to be collected and named. I have not examined the types.
Literature Cited
Brown, W. L., Jr. 1957. Biological investigations in the Selva Lacandona, Chiapas. 4. Ants from Laguna Ocotal (Hymenoptera: Formicidae). Bulletin of the Museum of Comparative Zoology 116:228-237.
Mayr, G. 1862. Myrmecologische Studien. Verh. Zool.-bot. Ges. 12:649-776.
unidentata s.s. was represented by abundant material from Mexico, Nicaragua, Costa Rica, and Panama.
JTL-008 was represented by material from Joachim Adis' canopy work in Amazonia, Terry Erwin's fogging samples from Tambopata, Peru, and additional material from La Selva in Costa Rica. This appears to be a mature forest canopy specialist, perhaps common in the Neotropics but infrequently encountered due to its restriction to the canopy.
JTL-009 was represented by one specimen from Chiriqui province in Panama. This species could be a narrow endemic, restricted to the wet forest of the Osa Peninsula and nearby parts of Panama. It could be an allopatric or parapatric version of JTL-008.
JTL-010 was represented by material from Venezuela, Peru, Brazil (Rondonia), and Bolivia. Dinah Davidson collected the species from Cecropia membranacea at Tambopata, and "river Cecropia" near Cocha Cashu. The Venezuelan specimens were quarantine interceptions, "ex Cattleya mossiae." This species appears to prefer cavities in live plants as a nest site, and seems to be most easily collected by looking in the internodes of Cecropia saplings.
One specimen from Iquitos, Peru, had surface sculpture like unidentata s.s., but the legs were brown. Legs were consistently yellow in all other specimens of unidentata s.s. I examined.
JTL-002 is another form that I did not discuss above, but seems appropriate here to round out the treatment of the unidentata complex. The head and mesomal sculpture and the color are similar to JTL-010. Unlike JTL-010, the petiole is more sharply margined and has more extensive longitudinal striations extending up the side. I made four nest collections of this species, all from one site in Trujillo Province, Venezuela, and all from the internodes of Cecropia saplings. This could prove to be an allopatric or parapatric version of JTL-010.
Overall, the picture that is emerging is one in which local communities may contain three species: (1) one that prefers open areas and is an opportunistic cavity nester; (2) one that occurs in mature forest canopy, and whose nesting habits are unknown at this point; and (3) one that is a live-stem specialist, and perhaps even a Cecropia specialist. The first one is morphologically uniform over its broad geographic range; the other two are widespread but show regional differentiation.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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