(Figs. 1, 2, 7, 10)
Formica apicalis Latreille 1802: 204.
Formica flavicornis Latreille 1802: 202. Synonymy by Brown (1957).
Pachycondyla apicalis (Latreille 1802); Mayr 1863: 439. First combination in Pachycondyla .
Pachycondyla flavicornis (Latreille 1802); Emery 1890: 58.
Neoponera flavicornis (Latreille 1802); Emery 1901: 47. First combination of flavicornis sensu Emery in Neoponera ; also first combination of apicalis sensu Emery (a misidentification of verenae Forel 1922) in Neoponera .
Neoponera latreillei Forel 1905: 161. Replacement name for Formica flavicornis Latreille 1802, j. hom. of Formica flavicornis Fabr. 1798. Synonymy by Brown (1957).
Neoponera obscuricornis r. latocciput Forel 1921: 132. NEW SYNONYMY
Neoponera obscuricornis latreillei (Forel 1905); Wheeler and Wheeler 1952: 613-615. Description of larva.
Neoponera apicalis (Latreille 1802); Brown 1957: 230; Kempf 1972: 161 (part); Fresneau 1985: 109-166; Fresneau and Dupuy 1988: 1389-1399.
Pachycondyla obscuricornis ; Reiskind 1977: 2-6. Not Emery (1890). Misidentification.
Pachycondyla apicalis (Latreille 1802); Goss et al 1989: 65-69. Revived combination in Pachycondyla , first use of implicit combination by Brown (1973).
Pachycondyla apicalis (Latreille 1802); Hölldobler and Wilson 1990: 385; Oliveira and Hölldobler 1990: 383-393; Soroker et al 1998: 1077-1090; Deitemann and Peeters 2000: 223-228; Longino2004.
Pachycondyla apicalis (Latreille 1802); Brown, in Bolton 1995: 302. Stated as “revived combination.”
Other material examined:
Bolivia . Santa Cruz : 10k NWTerevinto [ PSWC ] . Brazil . Amazonas : Ilha de Curarí [ LACM ] ; Ypiranga, R. Iça-Putomayo [ MCZC ] ; 300k EHumaita, Transamazonica Hwy [ PSWC ] ; Ponta Negra, N of Manaus [ MCZC ] . Bahia : CEPEC/CEPLEC, Rodovia Ilhéus / Itabuna [ ALWC , MCZC ] . Mato Grosso : Chapada dos Guimarães [ PSWC ] . Pará : Santarem, Taperinha [ MCZC ] ; Tucurui, Margem esq. [ LACM ] ; Utinga tract, nr. Belem [ MCZC ] ; “ Pará ” (s. loc.) [ MCZC ] . Rondônia : Porto Velho, Madeira [ MCZC ] ; Rio Madeira, Madeira Mamore R. R. Camp #39 [ MCZC ] ; Rio Madeira, Madeira Mamore R. R Co. Camp #41 [ LACM ] . Rio de Janeiro : Ilha Grande [ ALWC ] . São Paulo : Res. Florestal Caraguatatuba [ MCZC ] . Colombia . Chocó10 km SW S. Jose de Palmar, Rio Torito, Finca Los Guaduales [ MCZC ] . Guajira : R. Don Diego [ MCZC ] . Magdalena : Tayrona Park, S park boundary above Calabasos [ MCZC ] . Valle : km 98, old road Cali to Buenaventura [ MCZC ] . Costa Rica . Cartago : "Natrolista Platanillo", 1mi S Tuís [ UCDC ] ; Turrialba [ MCZC ] . Guanacaste : Guanacaste Cons. Area, Pitilla Research Station [ UCDC ] . Heredia : La Selva Biol. Sta. [ LACM , MCZC , PSWC ] ; P. N. Braulio Carrillo [ LACM ] . Limón : R. Toro Amarillo, vic. Guapiles [ MCZC ] ; Sarapiquí R., Oro Verde Lodge [ MCZC ] ; Zent [ MCZC ] . Puntarenas : Corcovado Nat. Park, nr. Rio Nino [ MCZC ] ; Corcovado Nat. Park, Sirena [ MCZC ] ; Palmar [ MCZC ] . Ecuador . Guayas : 10 mi. N.Manglar Alto [ MCZC ] ; 3 km SWBucay [ MCZC ] . Los Rios : Rio Palenque Biol. Sta. [ LACM ] . Morona-Santiago : Sucúa [ LACM ] . Napo : Misahualli [ MCZC ] . Pastaza : 2-8 mi. N.Puyo [ MCZC ] . Pichincha : ENDESA Forest Reserve [ ALWC , UCDC ] . Sucumbios : Limon Cocha & vic. [ MCZC ] . French Guiana . Cayenne : Paracou Experimental Forest, 45k W of Karou [ MCZC ] . Guatemala . Petén : Nacum [ MCZC ] . Retalhuleu : El Asintal [ UCDC ] . Suchitepéquez : Finca Los Tarrales [ ALWC ] . Guyana . Cuyuni-Mazaruni : Cuyani R. [ MCZC ] ; Kamakusa [ MCZC ] ; Kartabo [ MCZC ] . Upper Takutu-Upper Essequibo : N. Side Acari Mts. [ PSWC ] . Honduras . Atlántida : 14 km SLa Ceiba [ MCZC ] ; Lancetilla, nr. Tela [ MCZC ] . “Portillo Grande” (loc. indet.) [ MCZC ] . Mexico . Campeche : 10 Km ECampeche [ MCZC ] . Chiapas : Ocosingo, Laguna Ocotal Grande [ MCZC ] ; Ruinas Palenque [ LACM ] . Oaxaca : Temescal [ LACM ] . Quintana Roo : 13 km S Señor , Cenote de Tos Viriol [ LACM ] ; Cobá [ LACM ] ; Felipe Carillo Puerto, Cenote de Juan Coh [ LACM ] . San Luis Potosí : 18 mi S.Tamazunchale [ MCZC ] ; Huichihuayan [ MCZC ] . Veracruz : 2 mi W. Fortín , park cañon HWY 150 [ MCZC ] ; Cueva de la Sala de Agua [ MCZC ] ; El Palmar, 16 k W. Tezonapa [ MCZC ] ; Laguna Encantada [ MCZC ] ; Las Hamacas, 17k N Santiago, nr. Tuxtla [ MCZC ] ; Los Tuxtlas [ ALWC ] ; Presidio, Trail above Presidio [ LACM ] ; Pueblo Nuevo nr. Tezonapa [ MCZC ] ; Sa. Teoviscocla, nr. Cuichapa [ MCZC ] ; Tlacotalpan (as "Tapalcapan") [ MCZC ] . Yucatan : ChichénItzá [ MCZC ] ; 1 km NETixcancal [ LACM ] ; Actún Xpukil, 3k S Calcehtok [ LACM ] ; Grutas de Balankanche 4 km E ChichénItzá [ LACM ] . Nicaragua . Chinandega : (s. loc.) [ MCZC ] . Indio Mais Res., San Juan and Sarapiquí Rivers [ MCZC ] . “Tuli Creek” (loc. indet.) [ MCZC ] . Panama . Darien : Cana [ PSWC ] . Panamá : Barro Colorado I. [ LACM , MCZC , UCDC ] . Peru . Huánuco : 12 km SWTingo Maria [ LACM ] ; Cueva de Castillo nr. Tingo María [ LACM ] ; Monson Valley, Tingo Maria [ MCZC ] ; Tingo Maria & vic. [ MCZC ] . Loreto : Previsto [ LACM ] ; Quebrada Yanayaco, NE Iquitos [ LACM ] . Madre de Dios : Est. Biol. Cocha Cashu [ LACM , MCZC ] ; 15 k NEPuerto Maldonado [ MCZC ] . San Martín : Davidcillo, 30k NNE Tarapoto [ PSWC ] . Surinam . Raleigh Vallen-Voltzberg Res. Voltzberg camp [ MCZC ] ; “Surinam” (s. loc.) [ MHNG , 1w labeled “latreille Forel type ”] . Trinidad and Tobago . St. George : Caura [ MCZC ] ; Guanapo Valley Quarry Guanapo Rd. [ MCZC ] . Venezuela . Amazonas ? ("Terr. Amazonas"): 3 km N. of San Carlos de Rio Negro [ MCZC ] . Araguá : Rancho Grande [ MCZC ] . Barinas : 17k SSWCiudad Bolivia [ PSWC ] . Bolívar : 1k Sconfl. R. Nichare & Rio Caura [ PSWC ] ; Nichare Field Stn., Río Tawadu [ PSWC ] . Delta Amacuro : 140k NE Barrancas, Cano Mariusa [ LACM ] .
Worker measurements: (n = 19) HL 2.40-3.19, HW 1.96-2.72, SL 2.72-3.61, WL 3.96-5.17, FL 2.63-3.66, LHT 3.05-4.38, PL 1.04-1.36, PH 1.36-1.78, CI 0.77-.86, SI 1.28-1.47.
Worker diagnosis: A large species (WL> 3.9 mm) with the apical antennomeres colored bright yellow. Head somewhat longer than broad (CI 0.77-.86); mandibles elongatetriangular and bearing 12-15 teeth. Antennal scape longer than head length. Posterolateral margins of the propodeum rounded. Posterior and lateral faces of the petiole usually meeting at a rounded or an indistinct angle. Petiolar node relatively tall (PH> 1.35mm). Abdominal tergite 3 usually with erect setae, abdominal tergite 4 always with at least a posterior row of setae and often with additional setae. Hypopygium coarsely punctate posteriorly with shining interspaces in area adjacent to sting, bearing moderate to sparse subdecumbent pubescence not completely obscuring integument (Fig. 7). Body and appendages dark brown to black, except for yellow apical antennomeres.
This species may be separated from P. obscuricornis by the longer antennal scape and from P. verenae by the lack of posterolateral margination of the petiole.
Geographic variation: The shape of the petiole changes noticeably between localities. In one specimen from Guyana the petiolar form approaches the marginate condition of P. verenae . Specimens vary considerably as well in the development of abdominal pilosity. Ants from Central America often lack erect setae on abdominal tergite 3, while specimens from elsewhere in the range commonly have anywhere between 2 and 25 erect setae on tergite 3, with Peruvian specimens being the most pilose; a few of the most pilose Peruvian specimens have erect setae on the mesosomal dorsum and petiolar node. Eye size appears to vary slightly between localities as well.
Distribution: Southern Mexico to southeastern Brazil.
Biology: Pachycondyla apicalis is a common and conspicuous insect in many Neotropical forests. Most observations and collection records are of single foragers on the ground or on low vegetation. According to the collection data associated with museum specimens, P. apicalis occurs from sea level to 1600 meters (n = 40, median = 380 meters, mean = 642 meters). 14 collections were from primary or secondary rainforest or other kind of tall, moist forest. Two records were from rainforest edges and clearings, three from coffee plantations, one from cloud forest, and one from second growth thorn forest. This species has been observed nesting in rotting wood on or near the ground (Levings & Franks 1982, Dietemann & Peeters 2000, Longino 2004), in the ground (Levings & Franks 1982), and in the root mass of large Ficus trees within one meter of the ground (Fresneau 1985). One Colombian record in MCZC is from a Guadua sp.
Colonies are small, containing fewer than 200 workers (Fresneau 1985, Goss et al 1989, Dietemann & Peeters 2000), and monogynous (Dietemann & Peeters 2000). Dietemann and Peeters (2000) investigated the interactions between queens and workers, finding that workers can lay both trophic eggs and reproductive male eggs, some switching to reproductive male eggs in the absence of physical contact with the queen. Workers are apparently incapable of mating (Dietemann & Peeters 2000) and exhibit overt dominance interactions as well as egg-policing (Oliveira & Hölldobler 1990). Age polyethism in P. apicalis is described by Fresneau and Dupuy (1988). The formation of colony odor was studied by Soroker et al (1998), who tagged lipid precursors with radioactive tracers, injected them into ants, and conducted a series of experiments demonstrating that the molecules were spread through the colony by allogrooming of nestmates and not by trophallaxis.
Fresneau (1985) describes foraging behavior in a field population in Chiapas, Mexico. He found apicalis to be generalist predators and scavengers, collecting “20%… fruit debris and vertebrate carcasses and the remaining 80%…an assortment of 12 arthropod orders half of which were dead, and other half of which were living Lepidoptera and Coleoptera larvae.”(Fresneau 1985, pg 110.) Longino (2004) observed that foragers readily take crushed tabanid flies and lepidopteran larvae. A collection by E. O. Wilson from Veracruz, Mexico, records P. apicalis preying on termites, and two apicalis workers in the MCZC collection were found at a tuna bait in Guanacaste, Costa Rica.
Foraging is done individually, without recruitment, and individual foragers over time show strong fidelity to a particular area (Fresneau 1985). Tandem-running has been observed during nest relocation (Fresneau 1985). Orientation is probably visual (Fresneau 1985). Goss et al (1989) test an optimal foraging model using P. apicalis , concluding that foraging in the observed colonies is sub-optimal. Interestingly, a group of computer scientists have used the foraging behavior of P. apicalis as a model for creating an internet search algorithm ( Monmarché et al 2000).
Pachycondyla apicalis , as in other ponerine ants, subdues its prey by injecting venom through a sting. The venom may also have a defensive purpose and is described as tasting “bitter and burning” (Schmidt 1986). Cruz and Morgan (1997) investigate venom chemistry, Schmidt (1980) looks at venom toxicity, and Schmidt et al (1984) score P. apicalis sting-induced pain in humans as a “two” on a standardized ascending scale of one to four.
Pavan et al (1997) report on the auditory emissions of P. apicalis . As in most stridulating ants, the stridulatory organ is composed of a file on the fourth abdominal tergite and a scraper on the preceding tergite (Giovannotti 1996, Pavan et al 1997). Abdominal glands in the male are described by Hölldobler and Engel-Siegel (1982).
In Panama, P. apicalis serves as a model for the ant-mimic spider Castianeira memnonia(Koch) (Reiskind 1977). Reiskind (1977) reports the identity of the model as P. obscuricornis , but the voucher specimen at LACM is clearly P. apicalis . Additionally, his description of the yellow antennal apices and the photographs in the article unambiguously identify the ant as P. apicalis .
There is one record in MCZC of Pachycondyla apicalis in the gut contents of a leptodactylid frog, Eleutherodactylus biporcatus (Peters) , in Nicaragua.
The morphological evidence considered in conjunction with geography supports the separation of the P. apicalis complex into three species. All three are broadly sympatric from northern South America to southeastern Brazil, and the two more common species, P. apicalis and P. verenae , co-occur in Central America north to southern Mexico (Fig. 11). It is notable that every record of the rarer species P. obscuricornis involves sympatry with P. apicalis (2 sites), P. verenae (2 sites), or both (3 sites). Furthermore, 29 of 81 records of P. apicalis (35.8%) show sympatry with at least one of the other two species, and 29 of 60 records of P. verenae (48.3%) indicate sympatry as well. This pattern is likely to be an underestimate of local sympatry given that many records result from haphazard hand collecting and not from thorough myrmecological surveys. Sites that have been extensively surveyed (e.g., La Selva Biological Station in Costa Rica and the Mbaracayú Reserve in Paraguay) usually uncover at least 2 of the species.
Figures 12-17 illustrate some of the morphometric differences among these species. These differences are consistent across the entire range of the apicalis complex, including a number of sites where two or more species locally coexist. In particular, P. obscuricornis consistently has shorter antennal scapes than P. apicalis and P. verenae (Figs. 12, 13), a relatively broader head (Fig. 14), and a more pubescent hypopygium (Fig. 8). Pachycondyla apicalis can be separated from P. verenae by a taller petiolar node (Fig. 17), by a broader head (Fig. 16), by the lack of strong margination of the petiolar node, by the coloration of the antennal apices, and in South America (but not Central America) by the more extensive pilosity. Pachycondyla apicalis is usually larger in most measurements than P. verenae , but there is enough overlap that size alone is not always diagnostic. Given the strength and consistency of the morphological differences across multiple instances of sympatry, significant gene flow between these species is unlikely.
The common species P. verenae and P. apicalis both show considerable variation across their ranges in a number of characters, including petiole shape, head shape, scape length, eye size, and pilosity. This variation is either localized or broadly allopatric over a north-south cline, and thus in spite of the overall amount of variation there appears to be no justification for further division of the complex. In contrast, P. obscuricornis shows almost no variation across its range, suggesting a recent origin or a population bottleneck.
Phylogenetic relationships among the three species are unknown. Some characters, such as antennal scape length and hypopygial pubescence, suggest a closer relationship between P. apicalis and P. verenae , while others, such as mesosomal and petiolar configuration, indicate a relationship between P. obscuricornis and P. apicalis . Molecular genetic data will likely provide the most satisfactory resolution to the problem. Given the variation in the life-histories of these ants (e.g., monogyny in P. apicalis and polygyny in P. verenae ) and the amount of published biological information, a phylogeny could be of great utility.
Nomenclature
The amount of nomenclatural confusion in this complex is surprising considering the small number of species involved. Latreille (1802) described two similar species from South America, Formica flavicornis and F. apicalis . I have not seen type specimens of either, but the description of the shape of the node and the coloration of the antennal apices leaves little doubt about the identity of apicalis , a conclusion also reached by Brown (1957). The identity of flavicornis is not as clear. The name flavicornis is preoccupied by an older Fabricius (1798) species, and Forel (1905) provided Neoponera latreillei as a replacement name. Brown (1957) placed flavicornis and latreillei as a synonyms of apicalis on the basis of antennal coloration, a decision that I see no reason to challenge.
Emery was alone among previous workers in correctly recognizing three distinct entities, although he misapplied the name apicalis . In his 1890 paper “Voyage de M. E. Simon au Venezuela”, he discussed a form with a strongly marginate petiolar node (“ apicalis ”), a form with a more rounded node and yellow antennal tips (“ flavicornis ”), and a new variety of flavicornis with dark antennal tips (“ obscuricornis ”). Material determined by Emery in MHNG confirms that these names correspond to P. verenae , P. apicalis , and P. obscuricornis , respectively. Emery was content to keep the two forms with the more rounded node as varieties of a single species rather than as separate species, so he placed obscuricornis as a variety of flavicornis , and later latreillei as a variety of obscuricornis in “Genera Insectorum ” (Emery 1911) once Forel (1905) proposed latreillei as a replacement name for the preoccupied flavicornis .
Forel’s handling of the group parallels Emery’s but is less consistent. Examining the Forel collection at MHNG, I found that Forel largely followed Emery’s treatment of the species with the marginate node as apicalis and that with the yellow antennal apices as flavicornis / latreillei . Forel also provided new names for relatively slight variants, verenae from Panama as a variety of apicalis , and latocciput from Ecuador as a race of obscuricornis . Why he assigned latocciput to obscuricornis instead of latreillei is not clear, all the more so since he acknowledges both taxa in the brief description. It is apparent, however, that he put more consideration into form than coloration.
Brown’s (1957) primary contribution was the realization that Latreille’s original description of Formica apicalis matched the species that Forel and Emery had been calling first flavicornis and then latreillei . He put these into synonymy under apicalis . Brown evidently did not examine relevant specimens in either Forel or Emery’s collections, however, so he did not know that Emery and Forel used the name apicalis in a sense opposite to his own. This led him to infer erroneously that Forel’s Neoponera apicalis var. verenae must be a variety of Latreille’s apicalis instead of the oldest available name for the species with the marginate petiole.
Brown apparently did not see sufficient South American material prior to his 1957 publication to uncover the rarer species P. obscuricornis , as he lays out a case for the existence of “two and only two species” (Brown 1957, pg 231). Brown’s two species, “ apicalis ” and “ obscuricornis ”, are unambiguously apicalis Latreille and verenae Forel . Under his two-species dichotomy, Brown argued in the absence of type material that Emery’s obscuricornis could not be apicalis because of the antennal coloration. By default he treated it as the valid name for the other widespread species ( P. verenae [Forel] in the present study). Apparently Brown did arrive much later at a three-species conclusion that was never published, although it is unlikely he recognized the third species as being Emery’s obscuricornis (C. R. F. Brandão , pers. comm).
Brown’s reorganization was perpetuated in an unpublished but widely circulated manuscript key to Neotropical Pachycondyla . Consequently, the common species P. verenae has been misdiagnosed consistently as P. obscuricornis in the literature and in museum collections. In those cases where voucher specimens of “ obscuricornis ” were available in this study (Kempf 1972, Duelli & Duelli-Klein 1976, Wild 2003, Longino 2004), as well as in Traniello and Hölldobler (1984) which contained sufficiently detailed photographs, all records actually pertain to P. verenae . Since there are no collection records of true P. obscuricornis from Central America, it is almost certain that other MesoAmerican studies of “ obscuricornis ” (e.g., Fresneau 1984, Oliveira & Hölldobler 1991, Lommelen et al 2002) also pertain to P. verenae . More ambiguous are South American references (e.g., Wheeler et al 1999, Düssman et al 1996). Given the relative rarity of true P. obscuricornis , most South American records may also refer to P. verenae , but the identity of these cannot be verified without the examination of specimens.
Unfortunately, taxonomic instability may continue to persist for some time in the Pachycondyla apicalis complex. While the species-level nomenclature may stabilize with the recognition of three species, it is almost certain that the heterogeneous genus Pachycondyla is paraphyletic with respect to much of the rest of the tribe Ponerini (C. Schmidt, unpublished molecular data). As generic taxonomy falls in line with new phylogenetic hypotheses, it is entirely possible that various generic names, including Neoponera for the species discussed here, will be resurrected to retain monophyly of the ponerine genera.
