Martialis heureka

On the basis of the specimen’s external morphology, we are able to infer some aspects of the species’ biology. The pale integument and the absence of eyes suggest that M. heureka lives hypogaeically or in covered low-light environments, like leaf litter or rotting wood. The fact that the first two M. heureka individuals were collected in soil core samples during the day, and the present specimen in leaf litter at dusk, supports this hypothesis. Possibly, M. heureka surfaces during the night to forage. The unusually enlarged procoxae and long front legs could potentially be an adaptation to prey capture. Presumably, they are used less for digging activities, because the legs are relatively thin and lack the characteristic erect setae of actively digging species. We speculate that M. heureka might take advantage of preexisting underground cavities, like hollow rotten roots. The forceps-like mandible type is not seen in any other ant species. These long, filigree instruments could be used to drag soft prey items out of cavities. Annelids, termites, insect larvae, and other soft-bodied arthropods are possible prey. We do not expect M. heureka to prey on heavily sclerotized invertebrates. (Rabeling et al. 2008)

Identification
See the description given below.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Castes
Known only from the worker caste.

Nomenclature

 *  heureka. Martialis heureka Rabeling & Verhaagh, in Rabeling, Brown & Verhaagh, 2008: 14914, figs. 1, 2 (w.) BRAZIL. See also: Brandão, et al. 2010: 413; Kück, et al. 2011: 1.

We assume that the present specimen of M. heureka is a worker, because it lacks ocelli, the enlarged mesosoma and the extra sclerites associated with wings. In addition, the specimen was collected in the leaf litter suggesting foraging activity usually performed by the worker caste. However, queens with worker-like morphology have been reported from several poneroids and socially parasitic Formicinae and Myrmicinae. Because we did not perform a dissection of the single specimen no statement can be made about palpal segmentation or internal anatomy.

Worker
(holotype and only known specimen). Measurements:HW0.65 mm, HL 0.62 mm, SL 0.46 mm, FL 1.03 mm, ML 0.90 mm, WL 1.02 mm, PW 0.40 mm, PEW 0.19 mm, PEL 0.27 mm, PPW 0.34 mm, PPL 0.30 mm, HFL 0.60 mm, HTL 0.57 mm, CI 105, MI 145, SI 72, DI 45. Including the characters of the subfamily and genus description: small (HW 0.65, WL 1.02), pale yellow, and blind, integument in dried condition partly translucent. Very long, slender, forcepslike mandibles (ML 0.90, MI 145) inserted on outer anterior margin of head capsule, projecting straight forward to ~5/7 of its length, then curving slightly mesally. Inner margin bearing a tiny sudmedian tooth at ~2/5 of its length, measured from the base and a group of 3 subapical teeth at ~5/7 of its length: a median larger tooth and a somewhat smaller tooth to each side of it. The subapical teeth and the sharply pointed mandibular tip frame an oval space. Mandibles crossed in dried condition, not crossing in live individual or while stored in 80% EtOH. Head capsule bulbous in lateral view, narrowing toward posterior margin. Clypeus reduced, narrow strip between lateral head margin and wider between antennal sockets, covered with at least 20 setae that project forward, beyond the margin of antennal sockets, resembling a brush. Antennal scape relatively short (SI 72, DI 45), 1st and 2nd funicular segment 3⁄4 and 1⁄4 longer than 3rd funicular segment. Funiculus more than twice as long as scape. Mesosoma long and slender. Promesonotal suture present, pronotum and mesonotum presumably capable of movement relative to each other. Pronotum forming a slender cervix. Front legs enlarged: procoxae twice as long and wide as meso and metacoxae; profemura and tibiae also enlarged. Petiole subsessile with a short anterior peduncle; petiolar node rounded, smooth, with a short sloping posterior face; no teeth or projection ventrally. Metasoma (abdominal segment IV–VIII visible) laterally compressed, drop shaped in lateral view. Head, pronotum, and legs densely covered with erect to suberect hairs and sparsely with longer erect setae; mandibular pubescence dense, consisting of short suberect hairs. Inner margin with two rows of at least 18 long straight setae, which are arranged pair wise. Propodeum without any hairs; petiole with few suberect setae on dorsal surface of node and abdominal segment III–VIII with irregularly spaced long erect setae. Dense appressed pubescence absent from entire body. Only few body parts bear distinct sculpturing: neck, mesonotum, propodeum, and ventral surface of petiole punctate; lateral surface of propodeum faintly striate.

Type Material
Brazil: Amazonas, Manaus. Headquarters of Empresa Brasileira de Pesquisa Agropecua´ria (EMBRAPA)-Amazonia Ocidental, located at kilometer 28 of highway AM 010; 2°53'S, 59°59'W; elev. 40–50 m; 09 May 2003; col. C. Rabeling; ex leaf litter at dusk, primary tropical lowland rainforest. The holotype is deposited in Museu de Zoologia daUniversidade de Sa˜o Paulo, Brazil (MZSP).

Etymology
The species epithet heureka (gr.:I found it!) epitomizes the troubled story of the species’ rediscovery. Five years after two workers were discovered by M. Verhaagh in a soil sample and subsequently lost, a single worker, the present holotype, was recollected in a nearby patch of primary rainforest.