This species can be recognised by the absence of erect hairs on the scapes (small white erect hairs may be present), the presence of spines on the anterolateral angles of the pronotum (humeral angles) and the spine or tooth-shaped apical projection on the dorsal surface of the petiolar node (Fig. 2).

Figure 2.  

Dolichoderus debilis worker (LEUA-00000061181) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 (B, C).

Dolichoderus debilis has a Neotropical distribution. In Colombia, it has been recorded in the Departments of Antioquia, Bolívar, Guajira, Magdalena and Santander (Fernández et al. 2019), as well as in the Departments of Amazonas, Meta and Putumayo in the Amazon Region (Ortíz and Fernández 2011). It is reported here for the first time in the Department of Caquetá. In the Neotropical Region, the species has also been recorded in Bolivia, Brazil, Peru, Guyana, Suriname, French Guiana, Panama, Costa Rica, Guatemala and Mexico (Kempf 1959, Fernandez and Sendoya 2004).

The specimens were collected in an Andean Amazonian transition zone (Amazonian foothills) in the cloud forest. It has been recorded from the rainforest (Mackay 1993). Some observations suggest that D. debilis is associated with the ant genus Crematogaster and with termites of the genus Nasutitermes (Forel 1898, Wheeler 1936).

This species is one of the largest of the genus, recognised by the length of the maxillary palps which extend to the foramen magnum; furthermore, these ants have mesosoma extremely long and narrow, with the meso and metapleural longer than wide (Fig. 3).

Figure 3.  

Dolichoderus rugosus worker (LEUA-00000062446) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 1.0 mm (A); 2.0 (B, C).

This species shows a Neotropical distribution with records only for South America, in the Amazon rainforest (Ortíz and Fernández 2011). It is reported here for the first time in the Department of Caquetá. In Colombia, it also has a record outside the Amazon Region, in the Department of Antioquia (Ortíz and Fernández 2011). In the Neotropical Region, the species has also been recorded in Bolivia, Brazil, Ecuador, Peru, Guyana, Suriname and French Guiana (Kempf 1969, Fernandez and Sendoya 2004).

Specimens record here were found in the leaf litter in the Rio Hacha Basin, being the predominant ant species in this highly conserved area (Andean-Amazonian transition zone in the Department of Caquetá).

The genus Myrmelachista is recognised by its five-toothed mandible, 9 or 10 segmented antennae, with a 3 or 4 segmented antennal club and a wedge-shaped, erect, prominent and exposed petiole (Fig. 4).

Figure 4.  

Myrmelachista schumanni worker (LEUA-00000066482) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 (B, C).

Information on this species is scarce. In Colombia, it was known to be present, but without specific locality data (Fernández et al. 2019). It is reported here for the first time in the Department of Caquetá, in the Colombian Amazon Region. In the Neotropical Region, the species has also been recorded in Ecuador, Peru, Guyana and Venezuela (Kusnezov 1953, Frederickson 2005a, Salazar et al. 2015).

M. schumanni is recognised for its specific relationship with some plant species, forming the so-called Devil's gardens. This mutualistic interaction has been the subject of several studies (Frederickson et al. 2005, Frederickson 2005a, Frederickson 2005b, Frederickson and Gordon 2007), demonstrating the impact of this relationship in tropical rainforests. The collected specimen was sampled by leaf-litter sifting in a preserved area from a cloud forest. The presence of this species in leaf litter can be incidental due to the species' foraging behaviour on vegetation, which can result in its falling to the forest floor.

This species is easily distinguished by sharp spiniform teeth on the median clypeal lobe and regular longitudinal striate sculpture on the head, pronotum, mesonotum, sides of mesosoma and petiole (Fig. 5).

Figure 5.  

Adelomyrmex striatus worker (LEUA-00000066483) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 mm (B, C).

This record in the Andean-Amazonian transition zone of the Department of Caquetá represents the second record of the species in Colombia, suggesting a possible distributional restriction for the Amazon rainforest (Guerrero et al. 2018). In the Neotropical Region, the species has also been recorded in Ecuador, Peru and Brazil (Longino 2012).

Slow-moving ants difficult to distinguish from the substrate. All specimens were extracted from sifted leaf litter from the humid forest above 1200 m in the Andean-Amazonian transition zone studied.

The Colombian specimen presents yellowish, long and flexuous hairs on the body, but shorter than in the populations from Manaus (Amazonas, Brazil). A population from Peru presents variation in the teeth of the medial clypeal lobe, as well as finer sculpting in the frontal area of the head (Longino 2012).

This species is recognised within the genus Basiceros Schulz, 1906 by the following characteristics: head almost as broad as long, occipital lobes rounded with the relatively straight with a narrow mesal concavity, without presence of continuous crest; petiolar node and postpetiole completely covered with dense pilosity; petiolar node well developed and, in dorsal view, sub-rectangular; petiole with ventral carina with many developed teeth, of different shapes; first gastral tergite with few specialised hairs on its most posterior margin, those longer than basilar pilosity (Fig. 6).

Figure 6.  

Basiceros conjugans worker (LEUA-00000061876) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 1.0 mm (A, B, C).

This species has few records in the country, limited to the Departments of Amazonas, Meta and Nariño (Probst and Brandão 2022). It is recorded here for the first time in the Department of Caquetá. In the Neotropical Region, the species has also been recorded in Ecuador, Peru and Brazil (Probst and Brandão 2022).

This species was collected in leaf litter in the Río Hacha Basin. Additionally, it was collected on a log in leaf litter in cloud forest, although only one worker was observed. Probst and Brandão (2022) suggest that B. conjugans feeds on dead arthropods. Furthermore, it is thought that they may prey on termites, a behaviour observed in other species of the genus.

This species is recognised within the genus Basiceros by the following characteristics: rounded occipital margin forming a continuous elevated crest, posterior crest of the vertex emarginate medially which meets the medial convexity of the vertex (Fig. 7).

Figure 7.  

Basiceros disciger worker (LEUA-00000066499) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 1.0 mm (A, B, C).

This species is rarely collected. In Colombia, it has been recorded in the Departments of Meta and Norte de Santander (Probst and Brandão 2022). It is reported here for the first time in the Department of Caquetá. In the Neotropical Region, the species has also been recorded in Argentina, Brazil, Ecuador, Paraguay, Peru and Venezuela (Probst and Brandão 2022).

B. disciger is a common species in leaf-litter samples and widely distributed. A distinctive characteristic of this species is it presence in both highly conserved and degraded areas, unlike other species of the genus (Probst and Brandão 2022).

This species is recognised within the genus Basiceros by the following characteristics: occipital margin strongly emarginate generating two occipital lobes, mandible subtriangular, strongly bent ventrally, outer edges straight basally; mesoanapisternum strongly depressed (Fig. 8).

Figure 8.  

Basiceros scambognathus queen (LEUA-00000066497) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 1.0 mm (A, B, C).

This species was previously recorded in the Department of Amazonas (Fernández and Palacio 1995). It is reported here for the first time in the Department of Caquetá. In the Neotropical Region, the species has also been recorded in Brazil, Peru and Venezuela (Probst and Brandão 2022).

According to Probst and Brandão (2022), the unusual morphology of the mandibles of the species suggests specific predation conditions. However, records on its biology are limited to those obtained by Feitosa et al. (2007); a queen was observed preying on termites under artificial conditions.

The genus and species can be distinguished from any other Myrmicine ant by a posteromedian portion of abdominal tergum VI and anteromedian portion of abdominal tergum VII with several minute, cylindrical micro-pegs, each bearing a hair on apex (Fig. 9) (Fernández et al. 2014).

Figure 9.  

Kempfidris inusualis worker (LEUA-00000066487) A head in frontal view; B body in dorsal view; C body in lateral view; D Electron microscopy of micro-cylindrical pins. Scale bars: 0.5 mm (A); 1.0 (B, C).

Kempfidris inusualis is a Neotropical species restricted to the Amazon rainforest. In Colombia, it is only known from the Department of Amazonas (Castro et al. 2018). It is reported here for the first time in the Department of Caquetá. In the Neotropical Region, the species has also been recorded in Ecuador, Peru, Brazil and Venezuela (Fernández et al. 2014, Camacho and Feitosa 2016).

This species was collected in the leaf litter in secondary forest near a fallen log in an Andean-Amazonian transition zone in the foothills of Amazonia.

Fernández (2007) mentions that the morphological variability of the species is low, finding a variation in colouration, with more than one difference in the dorsal face of the propodeum and in the propodeal ridges, attributing this variation to the geographical distribution of the species.

This uncommon species is recognised by the following characteristics: inner surface of antennal scrobes and first gastral tergum smooth and shiny; body covered by long, flexible hairs; mesosoma covered fine, short striation; in lateral view, promesonotum strongly convex, superior to level of propodeum; propodeal spines less than twice as long as distance between their bases. The specimens collected in the eastern Amazon Basin are smaller than the Brazilian populations (Fig. 10) (Feitosa and Brandão 2008).

Figure 10.  

Lachnomyrmex pilosus worker (LEUA-00000066488) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A, B, C).

This is a Neotropical species reported from Brazil, Ecuador, Peru and Venezuela and is little known in Colombia with records from Amazonas, Meta and Nariño (Feitosa and Brandão 2008). It is reported here for the first time in the Department of Caquetá.

Species common in the leaf litter of humid forests, distributed from 200 to 1400 m elev.

This species can be recognised by its mesosoma smooth and shiny, with no erect hairs; propodeum with a pair of acute and well-defined spines; head foveolate, with median longitudinal striae (Fig. 11) (Fernández and Serna 2019).

Figure 11.  

Lenomyrmex inusitatus worker (LEUA-00000066496) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 (B, C).

This is the first record of the genus and species for the Amazon Region. The species was previously known from southern Colombia (Delsinne and Fernández 2011) and Ecuador (Salazar et al. 2015). This finding highlights the importance of studying ants in transition zones, as valuable information can be obtained about the distribution of species considered primarily Andean.

Unusual species, rarely collected. According to Delsinne and Fernández (2011), L. inusitatus inhabits mainly leaf litter and modified mandibles may be related to their being specialised hunter ants, although their prey is not known.

This species is known for having the first gastral tergite depressed above, compressed on the sides, sub-truncated and gibbous behind and body covered with white scales along the hooked hairs (Fig. 12).

Figure 12.  

Mycetomoellerius farinosus worker (LEUA-00000061972) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 1.0 mm (A, B, C).

Mycetomoellerius farinosus is a Neotropical species distributed in the Amazon rainforest (Ryder et al. 2010b). This is the first record of the species in Colombia. In the Neotropical Region, the species has also been recorded in Brazil, Ecuador, Peru, Guyana, Suriname, French Guiana and Venezuela (Mayhe-Nunes and Jaffe 1998, Silva et al. 2004, Youngsteadt et al. 2009)

Mycetomoellerius farinosus is a species commonly present in leaf litter in the Andean-Amazonian transition zone of the Hacha River Basin (Caquetá).

This species is recognised by the following characteristics: dorsum of mesosoma smooth and shiny, irregularly reticulate sculpture absent; length of head not clearly greater than width; pronotum convex and rounded above, propodeum and metapleuron with well-marked costulae; propodeum saddle-shaped; posterior border of the katepisternum and posterior face of the postpetiole smooth and shining; petiole anteroposteriorly compressed, scale-like (Fig. 13) (Albuquerque and Brandão 2004).

Figure 13.  

Oxyepoecus ephippiatus worker (LEUA-00000066491) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 (B, C).

This species is rarely collected, with only a few records from the Amazon rainforest (Albuquerque and Brandão 2004). This is the first report of the species in Colombia and the second report of the genus in the country, which was previously known from only a single record in the Department of Meta. In the Neotropical Region, the species has also been recorded in Brazil, Ecuador and French Guiana (Albuquerque and Brandão 2004, Salazar et al. 2015, Franco et al. 2019).

The only specimen of Oxyepoecus ephippiatus was collected in leaf litter in the Andean-Amazonian transition zone, in the lower cloud forest of the Hacha River Basin.

This species is recognised by the following characteristics: Head subtrapezoidal with angulated occipital corners; frontal lobes markedly expanded laterally and anteriorly, projecting over the clypeus and part of the mandibles; antennal scrobes deep, completely covered by lateral expansions of frontal lobes; promesonotum continuously rounded in profile; metanotal groove wide and shallow; propodeal spines short and acute; tegument hard with sculpture and coarse pilosity (Feitosa et al. 2008) (Fig. 14).

Figure 14.  

Stegomyrmex manni worker (LEUA-00000066492) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 mm (B, C).

Stegomyrmex manni is a Neotropical species widely distributed in Mesoamerica, but with scarce records in South America (Feitosa et al. 2008). This is the first report of the species in Caquetá and the second report of this species in the country (Serna 2002), marking the first record of the species for the Amazon rainforest region. In the Neotropical Region, the species has also been recorded in Ecuador, French Guiana, Honduras, Nicaragua, Costa Rica and Panama (Smith 1946, Kempf 1972, Ryder et al. 2010b, Franco et al. 2019).

The specimen was collected using the TSBF methodology, between 0 and 10 cm depth, which would suggest that this species inhabits the soil. This record complements the observations made by Feitosa et al. (2008), where they mentioned that S. manni is a soil inhabitant and is collected infrequently using Winkler bags. Here, we report, for the first time, the hypogeic habits in this species.

This species is recognised by having a mandible located in the middle of the anterior margin of the clypeus, without intercalary teeth, with a single proximal pre-apical tooth located near the mid-length; propodeal declivity with a narrow carina; a disc of the postpetiole and dorsum of first gastral tergite partially smooth with the presence of the basigastral carina; hairs of the first gastral tergite rigid; dorsum of the pronotum strongly rugose longitudinally; metapleural and lateral region of the propodeum smooth (Fig. 15).

Figure 15.  

Strumigenys incuba worker (LEUA-00000062105) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 mm (B, C).

This species has a restricted distribution, being recorded only from Ecuador and Colombia (Ryder et al. 2010b). In Colombia, it is known from the Departments of Cauca and Putumayo (Fernández et al. 2019). It is reported here for the first time in the Department of Caquetá.

The specimens were collected 0 to 10 cm deep in the soil in an Andean-Amazonian transition zone.

This species is recognised by the following characteristics: in frontal view, mandibles arising from the middle of the anterior margin of the clypeus; cephalic dorsum with a single pair of erect hairs, located posteromedially; Mesosoma in profile, propodeal declivity concave, upper and lower propodeal teeth narrowly proximal, joined by a short, broad lamella; bulla of femoral gland located dorsally in apical quarter of segment length, usually with faint oval patch-like appearance; first gastral tergite with numerous flagellate, suberect to erect hairs arising over entire tergite (Fig. 16) (Emery 1906, Bolton 2000).

Figure 16.  

Strumigenys prospiciens queen (LEUA-00000062105) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 mm (B, C).

Strumigenys prospiciens is widely distributed in South America (Bolton 2000). It is reported here for the first time in Colombia. In the Neotropical Region, the species has also been recorded in Brazil, Bolivia, Ecuador, Peru, Paraguay, French Guiana and Venezuela (Lattke and Goitía 1997, Bolton 2000, Wild 2007).

The queen was collected 0 to 10 cm deep in the soil in an Andean-Amazonian transition zone, using TSBF sampling methodology.

This species is recognised by being one of the largest of the genus with clypeus without a disc mound; basal third of mandible serrated, masticatory margin of mandible forming an obtuse angle with its basal margin; petiole distinctly longer than wide, anterior face perpendicular to dorsal face of petiolar node, which is an elongate and straight petiole with a prominent subpetiolar process apically rounded to subtruncate (Fig. 17) (Forel 1911, Franco and Feitosa 2018).

Figure 17.  

Centromyrmex gigas worker (LEUA-00000061955) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 1.0 mm (A, B, C).

This is the first record of C. gigas in Colombia. It has been previously reported from Brazil (De Oliveira et al. 2009) and French Guiana (Franco and Feitosa 2018). This record represents one of the northernmost occurrences of this species (Souza et al. 2012, Pereira Souza et al. 2015).

All specimens were collected at a depth of 10 to 20 cm in cloud forest, in the Andean-Amazonian transition zone of Caquetá.

The collected C. gigas specimens varied in pilosity concerning the type specimen (CASENT0907212). Some specimens were with dispersed pilosity, but no dense areas on the head and dorsum of the mesosoma, smooth and shiny scapes with erect pilosity restricted to the apex.

This species is recognised by having, in frontal view, inner basal margin of mandible markedly separated from anterior margin of clypeus (closed mandibles); hypostomal tooth visible in whole or in part; in lateral view, petiole with sharp apical tooth (Fig. 18).

Figure 18.  

Leptogenys unistimulosa worker (LEUA-00000061897) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 1.0 mm (A, B, C).

This species is widely distributed in the Tropics of South America (Lattke 2011). In Colombia, it is known from the Departments of Cundinamarca and Meta (Fernández et al. 2019). It is reported here for the first time in the Department of Caquetá. In the Neotropical Region, the species has also been recorded in Bolivia, Brazil, Ecuador, Peru, Guyana, Suriname, French Guiana and Venezuela (Lattke 2011).

Specimens were collected from a log on the ground, using the TSBF sampling method in an Andean-Amazonian transition zone.

This species is recognised by the fact that, in frontal view, the apex of the apical tooth of the mandible clearly exceeds the lateral margin of the head and the external margin of the eye (Fig. 19).

Figure 19.  

Thaumatomyrmex atrox worker (LEUA-00000066493) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 mm (B, C).

Thaumatomyrmex atrox is widely distributed in the Neotropical Region (Brandão 1991, Rodríguez and Lattke 2012, Albuquerque et al. 2021). In Colombia, T. atrox is widely distributed in the Andean and Caribbean Regions (Vergara-Navarro and Serna 2013), with a single record from the Department of Amazonas (Jahyny et al. 2008). It is reported here for the first time in the Department of Caquetá.

The specimen was collected in leaf litter from the lowest cloud forest in they Andean-Amazonian transition zone.

This species is distinguished by a small triangular projection of the medial clypeus, not projecting beyond the outline of the clypeolabral junction; further, ventral margin of petiole is less symmetrical (Fig. 20).

Figure 20.  

Wadeura holmgrenita worker (LEUA-00000061779) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 (B, C).

Wadeura holmgrenita was previously known from Peru (Madre de Dios and Cusco) (Branstetter and Longino 2022). Although W. holmgrenita is considered a rarely collected species, our collection data suggest that it is widely distributed in the Basin of the Rio Hacha. This record represents the second known occurrence of the species in South America and the first record in Colombia.

The workers were collected 20 cm deep on the ground in the cloud forest of the Andean-Amazonian transition zone in Caquetá. Delabie et al. (2000) mentioned that Wadeura species could be specialised predators of soil termites.

The Colombian population of W. holmgrenita match largely with the type material of the species, at least in the shape of the subpeciolar process, mandibles and clypeus. The specimens from Caquetá present a slight variation in pilosity, having erect and suberect pilosity on the lateral margins of the head and generating an appearance of dense pilosity.

This species is distinguished by the mandible triangular; ventral margin of petiole less symmetrical; ventral margin of petiole a triangular lobe with pronounced anterior tooth (Fig. 21).

Figure 21.  

Wadeura pauli worker (LEUA-00000061987) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A); 1.0 (B, C).

This is the first record of the species in Colombia, previously known from Guyana and Brazil, with records from only two localities, respectively (Branstetter and Longino 2022).

W. pauli was collected 20 cm deep on the ground, in the cloud forest of the Andean-Amazonian transition zone in Caquetá.

The population of W. pauli found in this study resemble morphologically the holotype, the shape of the subpeciolar process and dentition of the mandible matching the description of the species. Some specimens present a slight variation in pilosity, with areas of dense erect and suberect pilosity on the lateral margins of the head and dorsum of the mesosoma. In dorsal view, the petiole has a wider anterior face giving a trapezoidal shape to the petiole.

This species is distinguished from the other Probolomyrmex species by the presence of subpetiolar process well developed, ventrally concave to sub-rectangular, with the postero-ventral angle acute and directed towards the gaster; prora and protuberance on the posterior region of the first gastral tergite present. (Fig. 22)

Figure 22.  

Probolomyrmex kelleri worker (LEUA-00000066494) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A, B, C).

This is the first record of the species for Colombia. Previously, this species had been recorded in Guyana, Peru and Venezuela. (Oliveira and Feitosa 2019).

The specimens were collected in leaf litter in the cloud forest in the Andean-Amazonian transition zone of Caquetá.

We document here the first case for the species of an ergatoid queen (Fig. 23). The ergatoid queen has developed compound eyes and ocelli; further, the mesosoma is a little wider and higher than workers. The shape of the subpetiolar process in the ergatoid queen and the worker is identical, this feature being important to separate P. kelleri from any other species of this genus.

Figure 23.  

Probolomyrmex kelleri ergatoid (LEUA-00000066495) A head in frontal view; B body in dorsal view; C body in lateral view. Scale bars: 0.5 mm (A, B, C).