Typhlomyrmex

A small primarily neotropical genus. Workers are small, have reduced eyes and are rarely sampled. It appears all the species nest and forage within soil or rotting wood.

Identification
Lacau, Villemant & Delabie (2004) - The genus is morphologically homogenous, but there is interspecific variation in petiole shape, head shape, and body size (Brown, 1965; Lacau et al., unpublished data). The terricolous species are the smallest. Bolton (2003: 46) proposed the following potential autapomorphies for the genus: “workers eyes vestigial to absent,” and “male hypopygium with an elongate upcurved and median digitiform process.” The first character has been reported as homoplasic for the entire family by Baroni Urbani et al. (1992): the eye reduction occurs in many other ant genera with hypogaeic habits, in several subfamilies (Hölldobler & Wilson, 1990).

All Typhlomyrmex species share a cryptic ecology and reduced eyes, but it is unknown if this character represents an autapomorphy for the genus in the clade Ectatomminae and/or a convergent adaptation between different Typhlomyrmex species. The digitiform process on the male hypopygium, proposed as autapomorphic by Bolton, is uniformly present in Typhlomyrmex but also occurs in some Gnamptogenys. The digitiform process is possibly homologous in the two taxa (Lacau, unpub.) and should be considered homoplasic. Thus, no clear autapomorphy distinguishes Typhlomyrmex from other ectatommine genera and its position in this subfamily remains unclear.

Biology
Lacau, Villemant & Delabie (2004) - Compared to other poneromorph genera (sensu Bolton, 2003), Typhlomyrmex biology remains largely unknown but the rare available data reveal a strong ecological diversity between species. Although the distributions of individual species are highly variable, the genus has one of the largest distributions among the New World endemic poneromorph genera (Kempf, 1972). For example, the type species, Typhlomyrmex rogenhoferi which was described from Amazonas State (Brazil), is spread from northern Argentina to southern Mexico (Kempf, 1972; Longino, 1999; Lattke, 2003; Lacau et al., in progress). In contrast, others species have a much more reduced distribution and several are known only from a single locality. Typhlomyrmex meire is only found in a narrow part of the cocoa producing region of southern Bahia (Brazil). Typhlomyrmex prolatus and Typhlomyrmex foreli are two other endemic species respectively described from San Jose (Costa Rica) and Rio Negro (Brazil, Paraná State) regions (Brown, 1965). These restricted geographic ranges must be considered with circumspection owing to the scarcity and the disparity of the data concerning the diversity and the distribution of the Neotropical Formicidae (Kempf, 1972). In fact, ants remain undersampled in large areas of South and Central America. Many species currently regarded as rare or endemic could be relatively common in poorly known regions. This is particularly true for Typhlomyrmex species because they are all cryptobiotic, nesting and foraging within soil or rotting wood. The autoecology of Typhlomyrmex species appears as variable as their distribution. Typhlomyrmex rogenhoferi is an epigaeic species that colonizes large dead trunks lying on the rain forest floor (Lacau et al., 2001), while the others species are subterranean and terricolous. In particular, the small colonies of Typhlomyrmex pusillus nest in minute soil chambers (Brown, 1965; Lacau, pers. obs.); its biological cycle remains almost completely subterranean and only the winged gynes and males periodically emerge for mating.

The genus Typhlomyrmex is generally considered to be rare (Brown, 1965) because these ants are very difficult to find in the field. The terricolous species are rarely collected with extraction traps such as Winkler or Berlese-Tullgren collectors because workers only occasionally forage in the litter (Ward, 2000; Lacau, pers. obs.). Also they are not found in woody macro-elements of litter, such as little branches or dried fruits, nor in logs (see Carvalho & Vasconcelos, 2002; Delabie et al. 1997; Lacau, pers. obs.). The best technique to find living colonies is to look for individuals by careful hand fragmentation of soil elements.

Such laborious field collecting explains the scarcity of Typhlomyrmex specimens in museum collections, especially when compared with those of other poneromorph genera such as Pachycondyla and Hypoponera. Furthermore, the morphology of the different castes is rarely known. For example, Typhlomyrmex prolatus and Typhlomyrmex foreli are only known from their winged queen holotype. In the other taxa, the castes were frequently described separately, from material collected in different localities so that complete series including workers, queens and males coming from the same colony or even from a single location are extremely rare in collections.

Nomenclature

 *  TYPHLOMYRMEX [Ectatomminae: Typhlomyrmecini]
 * Typhlomyrmex Mayr, 1862: 736. Type-species: Typhlomyrmex rogenhoferi, by monotypy.
 * [Typhlomyrmex Gistel, 1856: 447. Nomen nudum; see Wheeler, W.M. 1911c: 858.]