Anillidris bruchi

Anillidris bruchi is known from limited number of collections in Argentina and Brazil. The workers are one of the most unusual in the subfamily, and are very similar to the formicine genus Acropyga. The morphological similarity of the Anillidris worker to workers of Acropyga is presumably a convergence caused by similar hypogeic habits (Shattuck 1992). A recent collection of this species (Schmidt et al 2013) was made in a hypogaeic pitall trap placed 50 cm below ground. This record confirms this ant lives a subterranean existence and greatly extends its known range. Schmidt et al. speculated A. bruchi could be found throughout the vast Paranaese phytogeographic province, which includes seasonal semidediduous rainforest habitats where this ant has been found.

Identification
Shattuck (1992) - (the following generic diagnosis is applicable for this Anillidris bruchi, the only species of the genus) Worker: Frontal lobes very close together; central region of clypeus raised, with a distinct medial trough and lateral ridges; compound eyes absent; palp formula 2:3; entire body covered with dense, short, erect pubescence. Known only from Argentina and Brazil. Queen: Palp formula 3:4; anterior clypeal margin with about 22 erect hairs. Male: Palp formula 3:4; mandible with 6 to 7 teeth, 1 denticle, and a distinct basal angle; fore wing with 2 closed cubital cells and 1 closed discoidal cell.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Paraguay.

Biology
Little is known about the habits of Anillidris. A colony has been collected under a large rock (Borgmeier 1937), while other data suggests that they are subterranean in moist areas (Kusnezov 1953b) and lestobiotic (Santschi 1937). The largest collection of workers was taken from a buried pitfall trap (Schmidt et al. 2013).

Nomenclature

 *  bruchi. Anillidris bruchi Santschi, 1936d: 414, figs. 21-28 (w.) ARGENTINA. Santschi, 1937c: 69 (q.m.). Combination in Linepithema: Kempf, 1972a: 135; in Anillidris: Shattuck, 1994: 3.

Description
Shattuck (1992):



Worker
HEAD. Vertex weakly convex. Compound eyes and ocelli absent. Antennae 12 segmented. Scape short, surpassing the vertex by less than one-third its length. Anterolateral clypeal margin even with the mediolateral region. Anteromedial clypeal margin entire, without a central notch or concavity of any type. Anterior clypeal setae about 4; short, less than twice the maximum scape diameter; moderately curved ventrally. Posterior clypeal margin even with or posterior to the posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Frontal carina present. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. Psammophore absent. MOUTHPARTS. Palp formula 2:3 (Santschi 1936). Mandible with 4 teeth and 3 denticles. Apical tooth subequal in length to the subapical tooth. Basal angle distinct, with a well developed tooth or angle separating the masticatory and basal margins. Basal margin smooth and without teeth or denticles. M ESOSOMA. Posteroventral pronotum lateral, rounded. Mesopleural process absent. Declivitous face of propodeum weakly convex; dorsal face convex, subequal in length to the declivitous face. Propodeal angle distinct. Mesosomal spines and tooth absent. Erect pro notal hairs numerous; very short, less than the maximum scape width. Dorsal promesonotal junction with the pronotum and mesonotum even. Metanotal groove reduced to a suture and with the mesonotum and propodeum forming a continuous, uninterrupted surface. Metanotal spiracle lateral and ventral of the dorsal surface when viewed in lateral profile. Propodeal spiracle lateral and ventral of the propodeal dorsum. Hind tibial spur with well developed barbules along entire inner surface (except extreme base). PETIOLE. Scale present; ridged and with a distinct angle dorsally; strongly inclined anteriorly and with the anterior face much shorter than the posterior face. Venter with a slight or weakly developed lobe. GASTER. First tergite damaged in available material. Fifth tergite ventral, gaster with 4 apparent tergites. GENERAL CHARACTERS. Worker caste monomorphic. Chromosome number unknown. Integument thin and flexible, weakly sculptured.

Queen
HEAD. Vertex weakly convex. Compound eyes relatively anterior on head. Antennae 12 segmented. Scape short, surpassing the vertex by less than one half scape length. Anterolateral clypeal margin even with the mediolateral region. Anteromedial clypeal margin entire, without a central notch or concavity of any type. Anterior clypeal setae about 22; short, less than twice the maximum scape diameter; straight. Posterior clypeal margin even with or posterior to the posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. Psammophore absent. MOUTHPARTS. Palp formula 3:4 (Santschi 1936). Mandible with 8 teeth and no denticles. Apical tooth slightly longer than the subapical tooth. Basal angle distinct, with a well developed tooth or angle separating the masticatory and basal margins. Basal margin smooth and without teeth or denticles. MESOSOMA. Posteroventral pronotum lateral, rounded. Episternal suture complete. Mesopleural process absent. Axilla parallel (very narrow across dorsal surface) and entire. Anterior axillar suture straight. Declivitous face of propodeum convex; dorsal face convex, subequal in length to the declivitous face. Propodeal angle indistinct. Propodeal suture absent. Mesosomal spines and tooth absent. Erect mesoscutal hairs absent. Propodeal spiracle lateral and ventral of the propodeal dorsum. Hind tibial spur with well developed barbules along entire inner surface (except extreme base). WINGS. Radial cell closed. Fore wing with 2 cubital and 1 discoidal cell. Hind wing with 2 cells. PETIOLE. Scale present; ridged and with a distinct angle dorsally; vertical and not inclined anteriorly. Venter with a slight or weakly developed lobe. GASTER. First segment vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception of the basal portion of the petiole. Fifth tergite ventral, gaster with 4 apparent tergites. Gastral compression absent (gaster circular in cross section). Fourth sternite flat across entire posterior border.

Male
HEAD. Inner margin of eye entire, flat. Scape length shorter than the length of funicular segments 2+3. First funicular segment barrel-shaped. Second funicular segment cylindrical, straight. Funicular segments 2 and 3 at most twice as long as broad. Third and fourth funicular segments straight. Anteromedial clypeal margin entire, without a central notch or concavity of any type. Anterior clypeal setae 6; short, about as long as the maximum diameter of the scape; straight. Posterior clypeal margin between the anterior and posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. MOUTHPARTS. Palp formula 3:4 (Santschi 1936). Mandible with 6-7 teeth and 1 denticle. Apical tooth slightly longer than the subapical tooth. Basal angle distinct, with a well developed tooth or angle separating the masticatory and basal margins. Basal margin smooth and without teeth or denticles. MESOSOMA. Posteroventral pronotum lateral, rounded. Episternal suture present, complete. Axilla parallel and entire. Anterior axillar suture straight. Declivitous and dorsal faces of propodeum convex. Propodeal angle indistinct. WINGS. Radial cell closed. Fore wing with 2 cubital and 1 discoidal cell. Pterostigmal appendage absent. Hind wing with 2 cells. PETIOLE. Scale present; ridged and with a distinct angle dorsally; vertical and not inclined anteriorly. Venter with a we" developed lobe. Attachment to gaster broad. GASTER. First segment elongated posteriorly, smooth and without a groove or indentation. GENITALIA. Pygostyles present. Posterior margin of subgenital plate with a 'V" -shaped notch. Paramere entire. Digitus linear, with a slight ventral arch. Ventral lobe of volsella present as concave lobe.

Type Locality
Loreto, Misiones Prov., Argentina.