Lenomyrmex

Lenomyrmex species have been collected from elevations close to sea level to 1800m but seem to be mainly restricted to mid-elevations (1100–1500m). Queen-worker dimorphism is weak, suggesting small colony sizes and absence of claustral independent colony foundation (Delsinne and Fernandez 2012).

Identification
The genus is characterized by elongate manidbles bearing a series of minute peg-like denticles that arise behind the masticatory margin, by frontal lobes that are poorly expanded laterally, by large and deep antennal fossae, and by pedunculate petiole, with a poorly defined node.

Distribution
Mid to high elevation rain-forests in southern Central and northwestern South America.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Biology
Delsinne and Fernandez (2012) - Lenomyrmex ants seem always locally rare and our collection of 34 workers (evergreen lower montane forest litter samples in an area near Podocarpus National Park at 1420m, Zamora-Chinchipe province, Ecuador in the Eastern Cordillera of the South-Ecuadorian Andes) is the first time that such a concentration of specimens have been collected within a relatively small area (400m2). A thorough inspection of the dead wood laying on the ground and of soil samples failed to uncover any nest of L. inusitatus. This and the fact that both workers and dealate queens were extracted from the leaf litter (Winkler method) may indicate that this species nests and forages in the leaf litter. The unusual morphology of the mandibles suggests that Lenomyrmex is a specialist predator on an unknown prey. This habit is possibly linked to its apparent rarity and restricted elevational distribution.

Two additional workers were found within a soil sample, at slightly higher elevation (1500 m), than the location where the the winkler sampled workers were found. The two workers were maintained alive during six days. They moved relatively slowly and feigned death when disturbed. They did not feed on any offered food items (alive and dead termites, millipedes, mites, various insect parts, sugar/water, tuna, biscuits).

Rabeling et al. (2016) - Lenomyrmex ants are rare in museum collections and the majority of the specimens have been collected sporadically in leaf-litter samples (Fernández and Palacio 1999, Fernández 2001, Longino 2006, Delsinne and Fernández 2012). So far only colonies of Lenomyrmex mandibularis have been collected manually because this species constructs nests in stems of a Palicourea species in the plant family Rubiaceae and in rotten logs (Fernández and Palacio 1999). In addition to systematic leaf litter sampling and hand collecting, the examination of stomach contents of leaf-litter foraging amphibians is a valuable source of cryptic and rarely collected ant species (Weber 1938, Delsinne and Fernández 2012, Sosa-Calvo 2015). Many species of amphibians and non-avian reptiles specialize on ant feeding and some species are predominantly myrmecophagous (Solé et al. 2002, Darst et al. 2005, Esteves et al. 2008). In the Neotropical poison frog family Dendrobatidae, myrmecophagy evolved at least twice, possibly three times independently (Santos et al. 2003, Darst et al. 2005), and the frogs sequester the skin alkaloids mostly from their ant and mite diet (McGugan et al. 2016). In addition to ants and mites, other arthropods, such as beetles and millipedes, are considered alkaloid sources for poison frogs (Dumbacher et al. 2004, Saporito et al. 2003, 2004, 2007).

To study the feeding ecology of the Little Devil poison frog, Oophaga sylvatica, the stomach contents of more than 300 individuals from different populations in Ecuador have been examined recently (McGugan et al. 2016, O'Connell, Sosa-Calvo et al., unpublished data). The majority of the frogs' diet consisted of ants, constituting between 40 and 86 % of diet volume in different frog populations. Of the more than 3000 examined prey items, 44 different ant genera could be identified, representing nine different subfamilies (Sosa-Calvo, O'Connell et al., unpublished data). The majority of the eaten ant genera belong to the subfamily Myrmicinae, including the rarely collected genus Lenomyrmex, with a total of nine specimens belonging to two species, Lenomyrmex hoelldobleri (the holotype worker) and Lenomyrmex foveolatus (seven workers and one gyne). Other cryptic and rarely collected ant genera include Leptanilloides, Stigmatomma, and Cerapachys, among others. To sample stomach contents of amphibians and other vertebrates solely for nutritional studies, it is not necessary to kill the animals. Stomach flushing methods have been developed and successfully applied in numerous studies, which avoids killing individuals of the study species (Solé et al. 2005). To conclude, the study of vertebrate stomach contents is not only a way of studying the trophic ecology of vertebrates themselves, but also an interesting source of cryptic and new arthropod species, including ants.

Nomenclature

 *  LENOMYRMEX [Myrmicinae: Lenomyrmecini]
 * Lenomyrmex Fernández & Palacio, 1999: 8. Type-species: Lenomyrmex mandibularis, by original designation.