FURTHER REVISIONARY STUDIES ON THE ANT GENUS MEGALOMYRMEX FOREL ( HYMENOPTERA : FORMICIDAE : MYRMICINAE : SOLENOPSIDINI )

I hereby revise, for the second time, the primarily Neotropical solenopsidine ant genus Megalomyrmex, describing M. wettereri n. sp., of the Silvestrii group, based on workers and gynes. Megalomyrmex latreillei Forel is synonymyzed under M. foreli Emery. The gyne of M. poatan is described and that of M. wallacei redescribed; males of M. acauna, M. incisus and M. wallacei are described. New locality records are given for M. ayri, M. cupecuara, M. goeldii, M. iheringi, M. modestus, and M. wallacei (Modestus group); M. acauna, M. balzani, M. cyendyra, M. emeryi, M. foreli, M. glaesarius, M. leoninus, M. staudingeri, and M. timbira (Leoninus group); M. poatan, M. silvestrii, and M. symmetochus (Silvestrii group), and M. drift, M. incisus, M. myops and M. pusillus (Incisus group). New biological data are recorded for M. acauna, M. goeldii, and M. wallacei. Comments are made for M. bidentatus, M. miri and M. mondabora.


INTRODUCTION
The 31 valid species of the ant genus Megalomyrmex are restricted to the wet and subtropical forests of South and Central America (Brandão, 1990).Since the publication of my revision of the genus (op.cit.), material from critical areas has accumulated in the collection of the Museu de Zoologia, Universidade de São Paulo (MZSP) and others that, combined with new information on the biology of some species, make it possible to resolve some issues left open, including the description of a new species, and castes of known species.Samples loaned from the Los Angeles County Museum (Roy R. Snelling -curator), the Instituto Humboldt (Bogotá, Fernando Fernández -curator), the CPDC -Centro de Pesquisas for museum collections.Collections newly studied are: LACM -Los Angeles County Museum of Natural History (Roy R. Snelling, curator), IHVL -Instituto Humboldt, Villa de Leiva, Bogotá (Fernando Fernández C., curator), INBC -Instituto Nacional de Biodiversdidad (INBIO on labels), Costa Rica (Jack Longino, curator), and CPDC -Centro de Pesquisas do Cacau, Comissão Executiva do Plano de Lavoura Cacaueira (CEPLAC), C.P. 7, Itabuna, BA, 45600 (Jacques Delabie, curator).Acronyms for collections follow Brandão (2000).
Unless otherwise stated, all studied specimens are deposited in the Museu de Zoologia da Universidade de São Paulo.Following also what has been done in the first revision (Brandão, op. cit.),I divided large series and redistributed specimens among collections to allow an efficient dispersal of duplicates.If the final destination of a given sample is not the MZSP, I acknowledge it under each species subheading.
I adopt also the terminology employed in Brandão (1990), but should correct the terms mesosternum and metasternum paired acrotergites to mesosternum and metasternum paired acrosternites, respectively.
The SEM images were made with a Leica 360 microscopy, after coating with gold.

RESULTS
The increasing use by myrmecologists of new collecting techniques for surveying the ant fauna in several localities of the Neotropics has been fruitful in the case of Megalomyrmex.In particular, rarely collected species, mainly the relatively small ones, have been recovered by submitting forest leaf litter samples either to Berlese-Tülgrem funnels or Winkler extractors, by attracting them to ground sardine baits, or recovering ants from sifted litter (see Brandão et al. 1999).It is interesting to note that even with significant sampling efforts in different habitats, all Megalomyrmex were collected only in wet and subtropical forests; it is also worthwhile to note that Megalomyrmex has never been collected from canopies using insecticide fogging techniques (Wilson, 1987), further indicating that Megalomyrmex are ground living ants that only inhabit the litter of wet and subtropical forests in the Neotropics.
The Megalomyrmex species groups adopted previously (Brandão, 1990) are followed here, as they proved to be useful in keying out the species sharing important biological and morphological traits.
The Modestus and Leoninus groups were separated from members of the other two groups in the 1990 key as having dental formula 1 + 4 and palp formula 4:3 in the worker caste (see Brandão, 1990, figs 9-16;49-59).It should be added that in both groups the preapical teeth show virtually identical development and the cutting blades of the mandibles lack a diastema.Some species of the other groups may have similar denticle counts but in this case the subapical teeth are unequal and often separated by a diastema.Jones et al. (1999) presented a table comparing the venom alkaloids in two species (M.modestus and M. goeldii) belonging to this group.New information regarding the species in this group follows.Brandão, 1990 Dr. Heraldo Vasconcellos collected two workers of Megalomyrmex ayri at Km 72, BR 174, Manaus, Amazonas state, Brazil (03°08'S, 60°01'W), in March 1990 (# 4642).A.B. Casimiro collected a worker and a gyne of M. ayri also in Manaus (# 4832 -Rs 2108 -E3).These are the first records of the species in Central Amazon, and the first records after the description of the species by Brandão (1990).Regarding the Modestus species group, only M. wallacei was previously recorded in the Amazonian basin.Megalomyrmex ayri appears to be uncommon in Manaus, as this locality has been intensively collected in recent years by several colleagues, and only these two samples have turned up thus far.

Megalomyrmex ayri
J. Delabie (CEPLAC, Itabuna, Bahia state, Brazil) sent me for study material collected in three localities in eastern Bahia state, Brazil: 3 alate gynes and a worker (# 4733) in Cachoeira, collected by G. Santos, in December 11, 1993, a worker from Ubatã (14°13'32"S, 39°27'56"W), collected by J.C.S. Carmo in December 27, 1996, and a worker from Ilhéus (# 4544B), collected by A.B. Casimiro in August 25, 1992.Workers of these three samples fit the definition of M. ayri since they show a clear suture between anepisternun and katepisternun.However, the Cachoeira gynes are problematically assigned as they present smooth mandibles.Also all other M. ayri samples come from Amazonian localities.For this reason, it is preferable to wait for more Bahian material before applying a name to these samples.Brandão, 1990 I considered the first funicular segment twice as large as the second, one of the characters that define the Modestus group of species (Brandão, 1990).However, in M. cupecuara workers, that agree in all other characters with other members of the Modestus group, the first segment is decidedly larger than the second, although never the double.

Megalomyrmex goeldii Forel, 1912
J. Delabie, sent me from CPDC a sample of M. goeldii, including workers and several "ergatoid" females collected in an old cocoa plantation located at Km 22 of the Itabuna-Ilhéus road (14 48'S, 39°16'W), Bahia state, Brazil.Reproductives are larger and darker than conspecific workers, and retain only the anterior median ocellus (as do ordinary gynes of this species), lacking any vestiges or scars of the lateral ones.Their mesonotuns bear a transverse impression (in side view) and the metanotuns can be clearly differentiated from other sclerites.The dorsal area of the anepisternuns and lateral margins of the katepisternuns bear rugulae.
I failed to notice any difference between workers of this sample and those of queenright colonies workers from southern localities.It is interesting to note that these are the only colonies from which ergatoids are known, and they come from the periphery of the species distribution, northern in this case.
Later on, J. Diniz visited the same locality (but in a specific location called Parque Zoobotânico) and found a Megalomyrmex goeldii colony with several ergatoids (voucher workers at MZSP).Unfortunately, we do not know if all of them were inseminated, as is the case for many other Megalomyrmex species.
Queenright colonies from southern localities may have several inseminated dealated gynes (see Brandão, 1990:424).I studied, from the same locality but unfortunately not from the same colony series, seven males collected by P. Terra in March 3, 1988 (# 4587).In these specimens the pronotum is strongly depressed, representing one extreme of the tendency already noticed in southern samples.Jones et al. (1999) compared the amount of different venom alkaloids present in M. goeldii ergatoid gynes and workers.
In July 1987, I collected 30 foraging workers of M. goeldii on a rotten stump in a dense evergreen primary Atlantic Forest reserve, Parque Municipal Baepi, Ilha de São Sebastião, São Paulo state, Brazil, 500 m of altitude (23°50'S, 45°18'W).Although I failed to locate the nest, this sample helped to confirm that, in workers from the southern end of the species distribution, the epipetiolar carina is not complete over the foramen (Brandão, 1990:424).
From the Los Angeles County Museum (LACM), I received three workers of M. goeldii from "Brazil" mounted on one pin, from the U.S. Quarantine at Hobboken, New Jersey, collected in July 16, 1947 by McMaster & Adams in wild Cattleya pur purata (# 47-10233).
I studied three workers of M. goeldii collected by M. Queiroz in a coffee plantation in Viçosa, Minas Gerais state, Brazil, in April 26, 1988 (20°45'S, 42°53'W), deposited in the MZSP.Soares et al. (1998) collected M. goeldii visiting sardine/honey baits set in a secondary growth semideciduous forest in the same locality.
Megalomyrmex goeldii seems to be fairly common in the localities where it has been recorded, but populations seem to be widely scattered.This may be related to the fact that in some populations of this species, the female reproductives are ergatoids, and hence dispersion is severely limited.These ants are easily attracted to baits, so it may be reasonable to conclude that they do not occur in places where they have never been found using baits.However, Yamamoto (1999) surveyed the litter ant fauna in the Estação Biológica de Boracéia, Salesópolis, São Paulo state, Brazil (23°39'26"S, 45°53'36"W), 843 m above sea level, an Atlantic Forest reserve pertaining to the MZSP.The author collected 132 individually sifted 1 m 2 litter samples submitted to Winkler extractors, obtaining a total of 95 ant species in 1304 records (record in this case means a species recorded in a given sample).M. goeldii was recorded 14 times in the survey (1.1% of all records), in a locality previously surveyed by sev-eral ant researchers and where specimens of M. goeldii were never found so far.Notwithstanding, M. iheringi (see below) has not been found recently in the E.B. Boracéia, a locality where it was still fairly common in the beginning of the twentieth century.
As part of an ongoing leaf litter ant fauna survey along the Atlantic forest, financed by FAPESP, A.A. Tavares (2002) collected 50 individually sifted 1 m 2 litter samples submitted to Winkler extractors for 48 hours, in Ribeirão Grande, Parque Estadual Intervales, Base Barra Grande, São Paulo state, Brazil, in February 5, 1999.Megalomyrmex goeldii was recorded four times in the survey.In Parque Estadual Serra do Mar, Núcleo Cunha-Indaiá Cunha, São Paulo state, Brazil (23°15'03"S, 45°00'26"W), Tavares repeated the procedure and recorded M. goeldii 20 times.The species seems to be one of the most common litter inhabiting ants in these localities.

Megalomyrmex iheringi Forel, 1911
The Estação Biológica de Boracéia, from where most of the few known samples of M. iheringi came from, is located some 70 Km in straight line from the previously mentioned Ilha de São Sebastião.This island is separated from the mainland by the relatively narrow São Sebastião Channel (less than 2 Km in the narrower width), and it is covered by vegetation which is very similar to that of the Serra do Mar.In my 1990 revision, I listed a worker of M. goeldii from Boracéia, although a re-examination of this individual led me to re-identify it as a very small M. iheringi.This raises doubts on the identity of M. iheringi, as I used overall size as the main diagnostic character between them.This was also the only locality where sympatry was ever recorded among these two species (see below).It seems premature to consider them conspecific given that the two species consistently differ in the length of the trunk.
I also studied a worker (CPDC collection # 143) from Parque Estadual Carlos Botelho, São Paulo state, Brazil (24°00'-20'S, 47°44'-48'W) collected with "Taz" (sic) bait by Y.M.B. Neptume in January 13, 1991.This collection was made probably around the headquarters of the Park.The latter covers parts of Eldorado Paulista, Sete Barras, Tapirai and São Miguel Arcanjo counties.This is an additional record of M. iheringi with consistently larger measurements of Weber's length of thunk than in any M. goeldii.

Megalomyrmex modestus Emery, 1896
The type locality of this species in Costa Rica is Suerre (near Jimenez) in the Limón province, and not in the Alajuela province as stated by Brandão (1990).
Three workers of this species, from Rio Toro Amarillo, near Guapiles, Alajuela province, belonging to the MZSP collection, were erroneously listed in the 1990 revision as gynes.Also from Costa Rica, I received from the LACM two workers of M. modestus collected in La Selva, Heredia province (10°26'N, 83°59'W), March 1974and August 4, 1974(# 0515-1740) in pitfall traps set at the forest litter by propodeum the sculpture is much stronger than in the other studied gynes.However, this Colombian specimen agrees in all other characters with M. modestus, and could represent a microgyne, expected in a genus like Megalomyrmex where female reproductives vary in size and development from typical alate gynes.A worker from the same sample agrees with other M. modestus workers.I also studied another worker of the same species, from the same locality (01 09'N, 77°68'W), collected by F. Escobar in 1994 (leg. # 39).

Megalomyrmex wallacei Mann, 1916
This species has been previously recorded only in the states of Amazonas and Rondônia in Brazil.Recently the MZSP received several samples from this species after the publication of my 1990 revision, extending M. wallacei known distribution.I had already commented on the extreme variation of the sculpturing pattern shown by specimens of M. wallacei, but should add that even the mandibles can be completely shiny and smooth, especially in samples from the northern part of its distribution.
I collected several workers, four gynes and three males (see description below) from four colonies, in September 27, 1987, Maracá Island (3°25'S, 61 40'W), near "Furo do Igarapé Firmino", more precisely near the mouth of this small creek into the Uraricoera river, state of Rodônia, Brazil.The colonies with up to 300 workers, one gyne, and immatures, live under dead leaves of the litter.Workers keep the larvae in between the mandibles.When disturbed, they spread out to rejoin after some minutes under a different leaf.R.R. da Silva and N.L. de Albuquerque obtained three workers of M. wallacei from a 1 m 2 sample of litter, submitted to Winkler extractor, taken from a gallery forest inside the savanna (cerrado) in Palmeirante, Tocantins state (formerly the northern half of Goiás state), Brazil (07 52'25"S, 47°57'07"W) in December 10 to 15, 2001.This sample represents the eastern record of the species and shows the smallest values in all measurements for workers of M. wallacei.

Gynes
In the 1990 revision, I stated that the gyne bodies are totally covered by rough punctures.However the samples studied and described herein furnished gynes with bodies mostly smooth and shining, while other individuals from other localities have bodies totally sculptured, or with intermediates between these conditions.In general, workers and gynes from the same colony share the same sculpturing pattern.In Maracás, for instance, the propodeal faces of both workers and gynes are covered by coarse transverse reticulations.

Males (first description)
Clypeus not swollen, smooth; mandibles smooth with four large teeth in the cutting edge, with some small denticles superimposed on the large ones; three equally developed ocelli with surrounding coarse sculpture; head otherwise smooth and shining, as the rest of the body; 2 nd to 5 th funicular segments darker than the others; mesonotum with parapsidial furrows, and notaulus; propodeum declivity much longer than basal face, declivity bears 3-4 concentric rugosities over the foramen and a complete epipetiolar carina; petiolar node compressed antero-posteriorly, with the lateral angles produced laterally; ventral process of postpetiole globose.

Leoninus group
In my 1990 paper, I said that instead of true winged gynes, members of this group present gamergates as the sole female reproductives.Although true winged gynes of the Megalomyrmex of the Leoninus group of species have never been found, yet the current nomenclature for wingless gynes in the Myrmicinae applies the term "ergatoids" to similar cases, meaning they are modified evolutionary descendants of winged gynes (see revision in Hölldobler & Wilson, 1990).However, until now I am not aware of any detailed study of the reproductive biology of any species of Myrmicinae in which the female reproductives are similar in size and shape to the sterile workers -a phenomenon that seems to be more common than previously believed.
In any case, permanent wingless female reproductives affect speciation, dispersion rates, and intraspecific variation, making the specific recognition rather problematic in this group of species.I would like to point out what I consider to be one of the most important results of wingless females, namely that colonies of Megalomyrmex of the Leoninus group of species do not construct or excavate nests, but rather occupy pre-formed spaces among rocks, under bark or within the leaf litter, readily moving away immatures when disturbed.This behavior also prevents their establishment in laboratory nests; in my experience there are no other myrmicine ants as difficult to keep in laboratory conditions as the species belonging to this group.As soon as they are transferred to artificial nests, each worker grabs an immature (or a group of them [if they are small enough]), and runs away to the nearest hiding place without any apparent coordinated behavior, to join nestmates only by chance afterwards.
In relation to the brief characterization provided in 1990 for females of this group, I should add that in larger specimens it is often possible to observe the small mesonotum spiracle openings, at the anterolateral dorsal border of the metapropodeal sulcus.Jones et al. (1999) described the pyrrolidine alkaloids found in extracts of two species in this group, M. cyendyra Brandão and M. latreillei Emery.Pyrrolidines are well known venom components of other myrmicine ants in general and have been detected also in M. leoninus.Brandão, 1990 This species was described from two samples collected in Gustavo Dutra and another locality in the Chapada dos Guimarães, near Cuiabá, Mato Grosso state, Brazil.Dr. Antonio Mayhé-Nunes visited the area recently and found out that Gustavo Dutra was actually the name of an Agricultural School.The small village is now known as São Vicente, and is located in the county of Santo Antonio do Leverger, some 100 Km East of the state capital, Cuiabá.

Megalomyrmex acauna
Megalomyrmex acauna is the only Leoninus group species recorded in the "cerrados".The Leoninus group is otherwise an entirely Amazonian group.In fact, Prof. Marcelo Tavares sent me recently a sample from the Indian Reserve Tadarimana, Rondonópolis, state of Mato Grosso state, Brazil (16°28'S, 54°38'W).I collected in May 6 to 29, 1996, two colonies of M. acauna in Uruaçu, northwestern Goiás, Brazil (14°17'06"S, 48°55'01"W).Both localities are situated within the "cerrado" biome.The ants live in fairly large colonies that occupy spaces among stones, in a way that is very similar to the most closely related species, M. balzani.In both cases the colonies were found along gallery forests and all attempts to rear them in the lab failed.

Male (first description)
Clypeus smooth without anterior denticle; cephalic integument smooth next to the compound eyes: first funicular segment similar in size to scape, second and third smaller; mesonotum with parapsidal furrows impressed, but no notaulus; epipetiolar carina complete; dorsal face of propodeum smooth; petiole compressed dorso-ventrally; petiolar spiracles laterally produced; petiolar and postpetiolar nodes almost indistinct; postpetiole without ventral process; genual plates rounded.

Megalomyrmex balzani Emery, 1894
J. Diniz and I collected in October 1, 1987, a large colony of M. balzani on the campus grounds of the Universidade Federal do Amazonas, in Manaus.Most individuals occupied a space hidden among the root system, litter and moss of a large tree, but a trail led to a space under bark some 1 m high on the live trunk, where part of the colony was found.The colony had more than 400 workers and several immatures, all brought alive to the Museu de Zoologia, but again, they did not survive for more than a few weeks in artificial conditions.P. Ward sent me a worker of M. balzani he collected in Fazenda Esteio, 80 Km northeast of Manaus (02°25'S, 59°46'W) (80 m), in September 15, 1987, (accession number 9150-2).
From Dr. Jacques Delabie, I received two workers of M. balzani (Ceplac # 302) labeled "Brasil: PA, origem provável".This represents the first record of this species in Pará state, where they do probably occur.
The AMNH collection houses a worker from Rio Purus, Amazonas state, Brazil, collected (date unknown) by A. Goeldi.The specimens belong to M. balzani and not to M. bituberculatus Fabricius as the label says.

Megalomyrmex bidentatus Fernández & Baena, 1997
This species was described based on workers collected by F. Escobar in two localities within the county of Barbacoa, Nariño province, Colombia (see localities description in Fernández and Baena, 1997): Tajadas, 1000 m (accession number 446), and Reserva Natural Río Nambí (see Escobar & Valderrama, 1995).Fernández deposited one specimen labelled as paratype from Rio Nambí at the MZSP, but in the original description, after giving information on the holotype, the authors say: "Obrera paratipo: Una obrera con los mismos datos del holotipo depositada en MZSPC; 13 obreras...", although in the measurements section they present figures taken from 13 "paratype" workers.I consulted Fernández, who agreed that their intention was to consider all 14 known specimens as types, so, with their agreement, I hereby correct this information, and thus consider also the specimens from the second locality as paratypes.
The original description includes characters I used to define the Leoninus group, except for the bidentate propodeum, which is apparently the only apomorphy for this species.Megalomyrmex foreli and M. timbira may have pointed propodeal angles, but never produced as pointed teeth as in the M. bidentatus paratype examined.To the original description I should add that the paratype lacks paired pointed acrosternites at the meso and metasternae.Also Fernández & Baena (op.cit.) rightly call attention to the shape of the head, which in this sample, is greatly modified in relation to other species in this group, being much longer than broad.
The only species in the Leoninus group recorded thus far in such high Andean altitudes is M. foreli (see below), which can be distinguished from M. bidentatus by the presence of a conspicuous sharp tooth on the ventral side of the postpetiole, that may be worn out (if so leaving a noticeable scar), but never completely lacking as in M. bidentatus.

Megalomyrmex cyendyra Brandão, 1990
Workers of M. cyendyra sometimes have the propodeal declivity mostly smooth, with very faint rugosities over the foramen, and the epipetiolar carina incomplete.The main diagnostic characters that separate this species from all other Megalomyrmex of the Leoninus group is the number of club segments (4-5) and the continuous promesonotum.
I studied three Colombian samples belonging to the IHVL collection collected in Reserva Nacional La Planada, Nariño province: two workers collected at 1800 m "interior bosque" (01°17'N, 78°15'W), one collected by F. Escobar and the other by C. Estrada; two with the same locality data collected from February to July, 1993, by C. Estrada; and two workers collected in the Parcela Olga by G. Oliva, in July 16 to 20, 2000, at 1850 m (01°15'N, 78°15'W).Jones et al. (1999) studied the venom alkaloids of M. cyendyra workers collected in July, 1997 in Borrero Ayerbe, Municipio de Dagua-Corregimiento, Departamiento del Valle, Colombia.

Megalomyrmex emeryi Forel, 1904
Until now, the only known specimen of the rather aberrant M. emeryi is a worker, the holotype, collected somewhere in Suriname (see Brandão, 1990).I tentatively assigned a male from southern French Guyana to this species, which has also aberrant characters in relation to the known males of other species in this group, and does not belong to any of the species in the Leoninus group known to occur in the region.It was with great surprise that I received from the LACM 6 workers clearly belonging to this rather distinctive species from Boquerón (500 m), Loreto, Peru collected by J. Schunke in July 7 to 14, 1965, and bearing a label that reads "M.latreillei Emery, R. Hamton det.".At first, I thought the extreme modifications could be the result of some kind of parasitism, but I am not aware of any case where parasitism might have resulted in such extreme modifications, particularly involving the characters that separate M. emeryi from all other taxa in this species group.Notwithstanding, since this new sample comes from a locality so distant from that of the holotype, I cannot rule out this hypothesis.
I. Zelner-Polania sent me for study three samples of Megalomyrmex of the Leoninus group from localities in Colombia that fill the gap in the known distribution of M. foreli and M. latreillei.These are: one worker from Caño La Curia, 580 m, Reserva Nacional La Macarena (02°45'S, 73°55'W), Meta province, collected by F. Fernández, two workers collected at the banks of Rio Guayuriba, Meta province, by Richter in December, 1950 to January, 1951, 500-700 m (03°55'S, 73°05'W), and six workers from Doncello, collected by Zelner-Polania in February, 1991.These samples are intermediate in all characters I thought could separate M. foreli from M. latreillei, including color pattern; therefore, I propose the synonymy of the former under M. foreli.The resulting taxon is very variable in character states otherwise constant in the genus, as the postpetiolar ventral process that, in certain localities (particularly in Colombia), can be strongly produced into a long and thin spine, lacking or completely worn out in specimens from other places, although the anteroventral margin of the postpetiole in this case is always sharp.This process wears out with age, leaving only a scar.
In these specimens, the gasters are concolorous with the rest of the body.The gaster is often darker in this species.Specimens from Costa Rica and Ecuador (limits of the known species distribution) are lighter in color than those from Colombia and Brazil (Acre).
From J. Delabie I received a worker (CEPLAC # 991) collected in Darien, Cerro Pirre, Panama, in August 26 to 30, 1991 by R. Ruiz.It is clearly a member of the Leoninus group.Megalomyrmex foreli is the only species in the Leoninus group that probably occurs in Panama, although I have samples only from Costa Rica and Colombia and not from Panama itself.This particular specimen, although too small in relation to all other samples of M. foreli studied so far, shows the color pattern of the Costa Rican samples of M. foreli, but lacks an anteroventral process of the postpetiole.As I have seen only one specimen, I refrain to describe it as a new species for the time being, hoping to study more material of the Leoninus group from Panama.Jones et al. (1999) studied the venom alkaloids of M. foreli (= M. latreillei) workers collected in Garza Cocha-Añyagu, 175 km eastern of Coca, Provincia de Sucumbios Ecuador in August 12,1994.I have not studied this material.
The locality record "Colombiana Farm" in Brandão (1990) is in the Alajuela province, and not in Santa Clara, as stated.Kempf, 1970 This species was known only from the type specimens from Llama, Cajamarca, Peru and from one sample collected 94 Km southwest of Cuencas, Nieves, Napo, Peru.I recently studied the first Colombian sample: two workers (IHVL) collected by F. Escobar at 1000 m in Tajadas, Barbacoa, Nariño, Colombia in May 1, 1994.These workers have the gaster with the same color as the rest of the body, while other samples of this species have the gaster decidely darker, almost shiny black, including the males from lago Agrio (see Brandão, 1990), not included in M. glaesarius for biogeographic reasons.However, in all other characters, the Colombian sample agrees with the diagnosis for M. glaesarius, extending further north the known distribution of this species.Nothing is known on the biology of M. glaesarius.
To distinguish M. timbira from M. staudingeri, as they seem to occur sympatrically at the Colombian-Venezuelan border, I used not only the peculiar propodeal shape in M. timbira, but also the fact that in M. timbira the petiole is almost twice as wide as the postpetiole, while in M. staudingeri, they are of similar width.The shape of the postpetiole is similar to that depicted in figure 83 in Brandão (1990), while the dorsal profile of the postpetiole is always evenly rounded.
To the original description, I should add that the epipetiolar carina in M. timbira is complete around the foramen, although in some specimens the carina almost fades out at the mid propodeal declivitous face.Some specimens are distinctly more hairy in relation to the type specimens and to other Megalomyrmex species in the Leoninus group.Brandão, 1990 M. cuatiara was described from the Colombian Amazon (Bolivar, Putumayo and Meta provinces); I have recently received from INPA two series with four and three workers respectively, both collected in Manaus by A.B. Casemiro in October 20, 1993(A3", # 4832 -Rs 2108), and in November 10, 1993 (N9", # 4832 -Rs 1202).Although there is no indication in the labels, Casimiro often collected ants sifting superficial soil and leaf litter samples, what can partially explain why this rather distinctive species has never been recorded before in Manaus -a place visited already by many ant specialists that traditionally collected mostly manually.These are the first non-Colombian records for M. cuatiara.

Megalomyrmex mondabora Brandão, 1990
The correct spelling for the type locality of this species is Turrialba, Cartago province, and not "Turialba" as stated in the original description (Brandão, 1990: 442).

Megalomyrmex poatan Brandão, 1991
Megalomyrmex poatan was described from a unique worker recovered from a leaf litter sample collected in San Pedro de la Sierra, Magdalena, Colombia submitted to Berlese.I received from the MCZ a second sample of this species, including 12 workers and one gyne (description below) from 15 Km north of Puerto Maldonado, Tambopata Province, Cuzco Amazonico, Peru, collected by S.P. Cover and J. Tobin (CA-27), elevation 200 m (12°36'S, 69°11'W).Three subsamples, including respectively three, two and one worker bear distinctive labels that read: "Camp.sifted litter from compost pile by trail to zone 1; Camp. in compost pile under bananas at forest edge, berlesate # 148; and seasonally flooded forest, plot ZUZI, flower fall, berlesate # 468".As for the workers, the main difference of these specimens in relation to the holotype is that the mesonotum is higher than the base of the dorsal face of propodeum in dorsal view.The anterior denticle of the petiole ventral face is not as developed as in the holotype, but can be seen with high magnification (80X).The petiolar postero-dorsal face has very faint rugosities, while the holotype shows conspicuous rugosities.83°36'W), 100 m, December 18, 1990 (2 workers) # 2769-S; and Reserva Biologica Hitgy-Cerere, provincia Limón (09°40'N, 83°02'W), 500 m, collected in August 30, 1985 (1 worker) # 970-S.The locality record for this species previously referred as Bataan, Santa Clara, Costa Rica in Brandão (1990)

Megalomyrmex symmetochus Wheeler, 1925
New records for M. symmetochus are as follows: Rio Manacapuim, Amazonas state, Brazil, collected in March 27, 1967 by the Expedição Permanente da Amazônia (MZSP), and recovered from MZSP Isoptera collection # 1382; one sample from the MCZ collected at 15 Km N of Puerto Maldonado, Tambopata Province, Cuzco Amazonico, Peru, in June 23 1989 by S.P. Cover and J. Tobin (CA-426), at elevation of 200 m.There are two workers of a minute attine Sericomyrmex with the same number are labeled as host for M. symmetochus.The type series of this species has also been collected within a nest of the much bigger Sericomyrmex amabilis (Wheeler, 1925:162).A sample from Belém (IPEAN), Pará state, Brazil, was recovered from an unidentified Trachymyrmex nest.
The locality record for this species "Hamburg Farm" as cited in Brandão (1990) is located along the Rio Raventazon, Limón province, Costa Rica.

Types
Holotype and five worker paratypes (La Selva) deposited at MCZ, Harvard; five paratypes (La Selva) and two paratypes (worker and gyne from Panama) deposited at the MZSP; five worker paratypes (La Selva) and one worker paratype (Panama) deposited at the USNM; two worker paratypes (La Selva) deposited at the BMNH.

Worker
Mandibles smooth, except for the coarse rugosities at the external area near the base (Fig. 1), dental formula 2+6; palp formula 3:2 (?); anterior clypeal border without median denticle; compound eye with 5 ocular facets at its largest diameter; occipital margin not raised; promesonotal suture not impressed dorsally (Fig. 2), mesonotum undistinguished from pronotum; metanotal groove longitudinally rugose; katepisternum smooth; propodeum spiracles laterally projected in an angle of 45° from the main axis of the body; base with divergent carinae at the meeting with propodeum sides, declivity smooth; epipetiolar carina not complete over the foramen; dorsal profile of petiole, in side view, evenly curved till apex of node, ventral face with a pronounced anteromedian double denticle (Fig. 3) originating in a non-translucent short longitudinal flange; dorsal margin of petiolar node, in frontal view, round; ventral process of postpetiole produced in a sharp tooth.
Color: uniformly bright yellow; apex of segments reddish.

Gyne
Three equally developed ocelli; mesonotum with notaulus; katepisternum distally rugose; propodeum dorsal face and declivity meeting in an angle similar to that of the conspecific workers; petiole and postpetiole also similar in shape and sculpture to the con-specific workers.

Diagnosis
The mandibular dentition and shape of propodeum distinguish M. wettereri, n. sp.from all other species in the Silvestrii group.

Comments
This is another Megalomyrmex of the Silvestrii group that inhabits the nests of fungus growing ants, in a peculiar lestobiotic relationship.The type specimens were found inside a nest of Trachymyrmex bugnioni (Attini), collected by J. Wetterer (Fig. 4), to whom the name of this species is dedicated, and inside a nest of Cyphomyrmex longiscapus in Panama collected by U. Mueller.Adams et al. (1998Adams et al. ( -1999;;2000) described the finding of two colonies of this new species in Panama containing healthy fungus gardens of C. longiscapus, although no attines were present at the time of collecting.According to these authors, laboratory observations revealed that the Megalomyrmex "consume the fungus by cropping mycelium from the garden substrate.However, they do not forage for and add nutrient substrates, or otherwise tend the fungus garden; thus, when the garden becomes depleted, Megalomyrmex sp. must locate and usurp new gardens in other attine colonies".When presented with active colonies of C. longiscapus, workers of this new species displace "host" workers in mass raids, stinging and ultimately killing the apparent defenseless C. longiscapus.When presented with C. longiscapus larvae in the laboratory, M. wettereri n. sp.workers strip them of the mycelium layer that naturally covers the cuticle, then place the larvae with their own brood.Adams et al. (1998Adams et al. ( -1999) ) considered this Megalomyrmex as a predator on C. longiscapus as they forcibly eject the resident attine to usurp their fungus gardens.Adams et al. (2000) described in detail how this species conducts mass raids to usurp gardens of C. longiscapus, then lives in the garden and consumes the fungi.Megalomyrmex wettereri n. sp.workers feed their larvae with attine brood only after removing the fungal mycelium that covers the attine larval integument, suggesting that this fungal coat may provide partial protection against predators.

Pusillus group
Workers of the species in this group are relatively small inhabitants of the leaf litter, and hence rare in collections, but the most prone to be collected using recently adopted techniques, such as the Winkler extraction apparatus, soil samples or Berlese funnels.From CPDC collection (sample # 1027), I studied a worker from Cuyabeno, Ecuador, collected by P. Caldwell from October 12 to January 05, 1994 (# 10726), and a worker (same accession number) from Nicaragua, collected by I. de Dramante, October 9 to 10, 1994 (# 8652).

Megalomyrmex incisus M.R. Smith, 1947
With the help of J. Lattke and E. Cancello I collected a colony of M. incisus in a dead twig on the ground in Caripe, Monagas province, Venezuela (10°10'N, 63°34'W), in a very wet afternoon (October 30, 1986).Only adult ants occupied the small chamber under the bark of the twig.The sample includes one dealated female (undescribed) and 28 workers.From the IHVL, I studied a worker from Caquetá Salzano, Colombia.
From the MCZ, I studied a sample of M. incisus including one dealate gyne and seven workers collected at Windblow Ridge, Arima Valley, Trinidad (elevation 1800') T-40, in May 15, 1988, collected

Gyne (first description)
Three equally developed ocelli; mesonotum with parapsidal sutures but no notaulus; katepisternum smooth; propodeum dorsal face and declivity continuous, with only one rugosity over the foramen; petiole ventral face with an anterior denticle, otherwise smooth; the postpetiole posterodorsal face has one continuous rugosity just before the socket, although rugosities are absent from the ventral face.Brandão, 1990 The type locality of this species is Zent, Limón province, Costa Rica.The specific locality is missing in the original description.

Megalomyrmex pusillus Forel, 1912
Of this rather rarely collected, although very distinctive species, I received from CPDC a worker collected in Poços de Caldas, Minas Gerais state, Brazil (21°48'S, 46°34'W), in October 28, 1991, by A.M.D. Aguiar.This is the first record of this species in Minas Gerais.

ACKNOWLEDGMENTS
This work would not have been possible without the generous support of several colleagues and, especially, my students, who sent me Megalomyrmex samples after the publication of my 1990 revision.I take this opportunity to thank them all together (see comments under each species).FAPESP and CNPq have been funding my projects over the years.CNPq financed a trip to Venezuela in 1986, and FAPESP a series of projects to the Brazilian Central Plateau and the Atlantic Forest, resulting in the collection of several specimens of Megalomyrmex.Dr. Nelson Jorge da Silva, from Universidade Católica de Goiás, in Goiânia, is acknowledged for inviting my students and me to participate in the survey project in northern Goiás, from where important specimens recorded in this addendum came from.James Wetterer kindly allowed me to publish the color picture, and to describe the specimens he collected inside a fungus growing ant nest.Jacques C.H. Delabie, Jack Longino and Fernando Fernandéz provided several specimens for this study, and information regarding their biology.Lara Maria Guimarães (MZSP) took the SEM pictures.Alexandre P. Aguiar, Ted Schultz, and an anonymous reviewer read earlier versions of the manuscript and suggested several improvements to the text.

FIGURE 1 .
FIGURE 1. Megalomyrmex wettereri n. sp.Paratype worker, head in frontal view, see measurements in the text.

FIGURE 3 .
FIGURE 3. Megalomyrmex wettereri n. sp.Paratype worker, petiole in oblique ventral view; note the shape of the ventral process; see measurements in the text.
by S. Cover and M. Moffett, "44 miles past end of Cooker Trace; secondary montane rainforest, about 20 years old, in rotten branch on forest floor".S. Cover already compared the workers with the paratypes of M. incisus M.R. Smith in the MCZ (S.Cover det.1990), with which I concur.
Santschi, 1925Soares et al. (1998) collected M. myops in Doane soil traps set in a secondary growth semideciduous forest and eucalyptus plantation in Viçosa, Minas Gerais state, Brazil.