Tatuidris tatusia

Tatuidris tatusia is the only species of the subfamily Agroecomyrmecinae. Their biology is largely a mystery, with collections typically consisting of a single worker being found in a litter sample.

Identification
Worker with a shield-like head having a broad vertex, ventrally-turned heavy mandibles which do not overlap at full closure, deep antennal scrobes with eyes at or close to their apex, compact and fused mesosoma, 7-segmented antenna, first gastral segment ventrally directed, and an antenna socket apparatus sitting upside down on the roof of the expanded frontal lobe. Reddish brown. (Donoso 2012). Between specimen variation can be rather large, as noted in the nomenclature section below.

Distribution
Neotropics, northern Mexico to central Brazil, French Guiana and Amazonian Peru. Most specimens and collections are currently known to occur in localities west of the Andes, with more collections tending to occur towards Central America and Mexico.

This taxon was described from El Salvador.

Habitat
Most collections come from mountainside (pre-montane) areas at mid elevations (usually 800–1200m of altitude). Collections from lowland Amazonia are few.

Biology
Donoso (2012) - Little is known about the biology of the ant genus Tatuidris and, until recently, no observations of live specimens were registered. Details of a first collection event of a small live colony (3 workers and 4 gynes) by Dr. Thibaut Delsinne (pers. comm.) in a mid-elevation forest in southeastern Ecuador suggest that Tatuidris may well be a highly specialized predator, as colonies kept in captivity did not accept any food item offered to them. Food items rejected by the ants included live and dead termites, millipedes, mites, various insect parts, sugar water, tuna, biscuits, live and dead fruit flies (Drosophila), live springtails, live myriapods (Chilopoda and Diplopoda), live and dead Diplura, small live spiders, small live pseudoscorpions, one small snail, uncooked hen egg (i.e. piece of cotton wool soaked with fresh whisked hen egg; Brown 1977), ant larvae (Gnamptogenys sp.), and live ant workers (Cyphomyrmex sp., Brachymyrmex sp.). Potential food items (arthropods) for Tatuidris were taken from soil samples and Winkler samples (following Silva and Brandão 2010) collected at the site where Tatuidris was a priori determined to be present.

Further observations by T. Delsinne suggest that T. tatusia may be a sit-and-wait predator, as “both workers and gynes moved very slowly and were very clumsy. They often remained motionless during several tens of seconds or even several minutes when disturbed (either by my handling or by the contact with another arthropod). It is difficult to see them as powerful predators!” (pers. comm.). These observations were mainly performed at night, suggesting that T. tatusia may be nocturnal, a hypothesis also supported by collection patterns. For example, in the Río Toachi forest of Ecuador T. tatusia specimens tend to fall in pitfall traps, instead of Winkler sacs (Donoso and Ramón 2009). Because pitfall traps usually work 24-h, but Winkler sacs generally uses litter sifted during the day, then ants with nocturnal habits may be under represented in Winkler samples. The small eyes of Tatudris species provide further support for this hypothesis.

Nomenclature

 *  tatusia. Tatuidris tatusia Brown & Kempf, 1968: 187, figs. 1-4 (w.) EL SALVADOR. Senior synonym of kapasi: Donoso, 2012: 69.
 * kapasi. Tatuidris kapasi Lacau, Groc, et al., 2012: 2, figs. 1-6 (w.) FRENCH GUIANA. Junior synonym of tatusia: Donoso, 2012: 69.

Type Material


Donoso examined many specimens (118 specimens from 52 collection events). He found quite a range of variation within specimens but felt this still represented a single species. He reported the following notable variation among the samples examined:

Pilosity variability Currently, four striking pilosity patterns are known to occur within Tatuidris collections. Pilosity pattern A consists of a mix of both long flexuous and short appressed setae. This is the most common pilosity pattern and the one that most resembles the type specimens from El Salvador and the gyne from Otongachi, Ecuador. Pilosity pattern B is characterized by very short, fully appressed, and regular spaced setae arrayed homogeneously and equidistantly on the head, mesosoma, petiole, postpetiole and gaster. Pilosity pattern C is characterized by dense lanose-looking setae. Pilosity pattern D consists of short and uniform decumbent (strongly inclined but not fully appressed) setae scattered throughout the body.

Size Specimens of T. tatusia are small (average WbL = 0.62mm), but specimens can vary greatly in size, with larger specimens being twice as large as the smaller ones (min WbL = 0.45 mm, max WbL = 0.90 mm). Size variability within trap catches (possibly same colonies) may be considerable. For example, workers from one collection catch in Nicaragua (collection series MGB#1179) varied 30% in size (WbL from 0.65 to 0.85 mm). It is still unclear whether intra-colony size variation is due to the presence of morphological worker castes (e.g. minor and major castes) or continuous size variability. A PCA analysis revealed that most variability among specimens is related to size.

Sculpture The strength and depth of all sculpture patterns is accentuated in larger sizes. Collections from Nicaragua also tend to present more accentuated sculpture patterns. The head dorsum is usually smooth and shining, except for the area below eyes, which presents longitudinal carinae. The head vertex is covered with transverse carinulae. The lateral surface of the mandible is smooth and shining except for longitudinal superficial striae on the side that vary in depth. The antennal scape is shagreened and superficially areolate. The surface of the ventrolateral part of the pronotum varies strongly across specimens, from smooth and shining to strongly striate, or carinulate. The dorsum of the mesosoma has concentric carinulae and sometimes is slightly punctate. The mesopleuron is smooth and shining except for punctuations and areolae on the ventral margin. The propodeal declivity is smooth with fine transverse striae. The petiole and postpetiole are dorso-laterally strigulate. The gaster is mostly smooth and shiny but sometimes finely and sparsely strigulate.

Eyes The relative position of eyes is highly variable within the species. For example, eye location ranges from being completely within the antennal scrobes to completely outside the scrobes (Figure 1b). In some cases (specimen J.Longino#2088-S) the eye itself is located outside the antennal scrobe, but the eye’s fossa is well marked and confluent with the antennal scrobe. In most specimens, the antennal carina bifurcates from the antennal scrobes and lies straight above the eyes. However, in specimens from Nicaragua (MGB#1179 colony collection), a strongly impressed antennal carina is present. In these specimens about 40% of the eye’s area lies within the antennal scrobes. In the gyne, only ~1/6 of the eye lies within the antennal scrobes. A depression sometimes forms in the integument in the sides of the propodeum, below the propodeal spiracle and above the metapleural gland. The depth of this depression varies among specimens and tends to be deepest in larger specimens.

Worker
Donoso (2012) - HW = 0.56–1.10mm. Body short and compact. Color ferruginous to dark red. Integument thick and rigid. Body covered by hairs, which are variable in length and inclination. HEAD. Head shape pyriform, broadest behind. Maxillary palps one-jointed. Labial palps two-jointed. Labrum bilobed, broader than longer, capable of full reflexion over the buccal cavity. Mandibles opposing in most of their border (except in the tips of the masticatory margin). Masticatory margin with two blunt apical teeth overlapping at closure. Setae (mandibular brush) abundant, present on the ventral side of mandibles. Antenna 7-segmented. Antennal club two segmented, well developed. Scape clavate, gently downcurved at base. Torulus with hypertrophied dorsal lobe and strongly curved downwards. Antennal scrobe present. Antennal socket and antennal scrobe confluent. Antenna socket apparatus sitting upside down on the roof of the expanded frontal lobe. Eyes present, small (REL= 5.41–11.48), located at the posterior apex of antennal scrobe. MESOSOMA. Promesonotal suture fused. Metapleural gland orifice round. Metapleural gland opening visible. Metapleural gland bulla separated from annulus of propodeal spiracle by more than the diameter of the spiracle. Katepisternal oblique groove absent. Lower mesopleuron with longitudinal costulae. Propodeum unarmed. Propodeal spiracle, in profile, located at about mid-length of sclerite. PETIOLE and POSTPETIOLE. Petiole short and sessile. Petiolar ventral process large and rounded. Petiole dorso-ventrally fused. Petiole broadly attached to postpetiole (abdominal segment III). Postpetiolar tergum and sternum overlapping at junction. Postpetiole in dorsal view wider in posterior half. GASTER. Articulation between postpetiole and gastral segment 1 (abdominal segment IV) broad. Postpetiolar postsclerites not set in a concavity or depression. Pretergite of first gastral segment with neck-like constriction. Stridulitrum present on first gastral segment. Limbus (i.e. anterior transverse cuticular ridge of the first gastral segment) absent. Suture between first gastral tergite and sternite anteriorly rounded. First gastral tergosternal suture strong, but not fused. Base of the first gastral sternum in profile rounded. First gastral sternite length is reduced, such that tergite is much larger than the sternite and strongly vaulted. First gastral tergum and sternum smooth or with scattered puncta. Sting present. LEGS. Mid and hind tibial spurs present.

Measurements (in mm) and indices: [average (min–max) of 10–58 specimens]: AScL 0.46 (0.31, 0.67); AScW 0.24 (0.18, 0.36); CIx 129.03 (117.07, 137.93); EL 0.05 (0.03, 0.08); FL 0.43 (0.31, 0.70); FW 0.11 (0.08, 0.17); HL 0.59 (0.43, 0.88); HW 0.76 (0.56, 1.10); IAD 0.36 (0.25, 0.54); PL 0.16 (0.10, 0.24); PpL 0.16 (0.10, 0.25); PW 0.25 (0.18, 0.37); PpW 0.36 (0.26, 0.53); PPpIx 68.92 (58.14, 80.00); PrW 0.52 (0.38, 0.77); TiL 0.35 (0.27, 0.52); TiW 0.10 (0.06, 0.17); WbL 0.62 (0.45, 0.89); SL 0.42 (0.32, 0.51); SW 0.13 (0.11, 0.17); SI 329.82 (300.00, 360.00); REL 9.02 (5.41, 11.48).

Queen
Donoso (2012)- Gyne: HW = 1.28mm. Body short and compact, with exterior morphology and characters similar to workers. Body covered by hairs. Color yellow, paler than workers. Integument thick and rigid. HEAD. Head shape pyriform, broadest behind. Vertex straight, not concave. Labrum bilobed, broader than long, capable of full reflexion over the buccal cavity. Mandibles opposing in most of their border, except in the tips of the masticatory margin. Masticatory margin with two blunt apical teeth overlapping at closure. Mandibular setae present but less abundant than in workers. Antennal joints 7-segmented. Antennal club two segmented, well developed. Scape clavate, gently downcurved at base. Antennal scrobe present. Antennal socket and antennal scrobe confluent. Antenna socket apparatus sitting upside down on the roof of the expanded frontal lobe. Eyes present, EL = 0.20mm, eyes larger than in workers (REL = 22.63), located laterally at posterior border of antennal scrobes. Lateral ocelli and median ocellus present. WINGS. WingL=4.60mm, about 60% longer than total body length. Forewing well developed, with costal cell, basal cell (radial), sub-basal cell (cubital), no vein present between sub-marginal cell 1 and sub-marginal cell 2, R1 vein surrounding sub-marginal cell 3, discal cell 1 and discal cell 2 present, divided by cubital vein which extends a distance similar to the inferior edge of discal cell. Hindwing well developed, with Cu-a vein present. Basal cell completely surrounded by M-Cu and and rs-m+M veins. MESOSOMA. Promesonotal suture present, not fused. Scutellum broad. Anepisternum and katepisternum broad and shiny, not sculptured. Propodeum armed with a small posteriorly directed spine. Propodeal spiracle in profile at about one-diameter from posterior edge. Metapleural gland present, metapleural spiracle big, longer than broader, within a dorsally directed fold. PETIOLE and POSTPETIOLE. Petiole broadly attached to postpetiole (abdominal segment III). Postpetiole in lateral view much shorter than gaster (abdominal segment IV). GASTER. Shiny. Vaulted. Constriction between postpetiole and gaster present. Abdominal sternum IX simple, triangular in shape, without spines or lobes. Sting present. LEGS. Mid and hind tibia with pectinate spurs present.

Measurements (in mm) and indices: (n=1) AScL 0.47; AScW 0.15; EL 0.20; FFS 0.09; FL 0.77; FW 0.20; HL 0.88; HW 1.28; IAD 0.56; Pl 0.22; PPL 0.28; PPW 0.72; PW 0.45; TL 0.69; TW 0.20; WingL 4.60; WbL 1.53; REL 22.63.

Male
Donoso (2012) - HW = 0.88mm. Body compact, with exterior morphology (except head) similar to workers. Body covered by decumbent setae. Color dark. HEAD. Dorsum with scrabrous-strigate sculture. Lateral ocelli and median ocellus present. Antenna 12-segmented. Antennal sockets exposed, not covered by frontal carinae, at mid-length from the anterior border of clypeus and the head posterior vertex margin. Antennal scrobes absent. Antennal carinae absent. Scape very short, about 1.3 times as long as pedicel. First flagellar segment relatively short, about the same length as pedicel, slightly curved at base. Antennal club absent, but apical segment is at least 2 times longer than preceding segment. Mandibles reduced, falcate, without differentiated masticatory and basal margins. Mandible edentate, with no visible apical tooth. Clypeus broad, with straight anterior margin. Clypeus does not extend to space between eyes. EL = 0.32mm, eyes larger than in workers (REL = 48.44) located at mid-length at lateral margin. WINGS. WingL = 3.6mm, about 50% longer than total body length. Venation and cell composition of both fore- and hind-wings similar to that of gyne. MESOSOMA. Oblique mesopleural furrow close to but not reaching pronotum. Mesonotum notauli absent. Mesoscutum and mesoscutellum mostly shiny, with small foveae. Pronotum with rugae. PETIOLE and POSTPETIOLE. Constriction between petiole and postpetiole (abdominal segment III)present. Petiole and postpetiole similar in shape to worker petiole and postpetiole. Petiole broadly attached to postpetiole. Postpetiole, in lateral view, much shorter than gaster (abdominal segment IV). GASTER. Shiny. Vaulted. Constriction between postpetiole and gaster present. Abdominal sternum IX simple, triangular in shape, without spines or lobes. LEGS. Hind tibia with 1 pectinate spur.

Measurements (in mm) and indices: (n=1) EL 0.32; FFS 0.13; HL 0.66; HW 0.88; IAD 0.21; ScL 0.11; WingL 3.6; WbL 1.22; FL 0.9; REL 48.44.

Type Material
The collection of Tatuidris tatusia was made by Berlese funnel from humus, and the sample also contained specimens of a small Solenopsis, an undescribed species of Eurhopalothrix, and Octostruma balzani.

Additional References

 * Billen, J. & Delsinne, T. 2013. A novel intramandibular gland in the ant Tatuidris tatusia (Hymenoptera: Formicidae). Myrmecological News 19: 61-64.
 * Donoso, D.A. 2012. Additions to the taxonomy of the armadillo ants (Hymenoptera, Formicidae, Tatuidris). Zootaxa 3503: 61–81.