Nylanderia metacista

The type material was collected from a nest under the bark of a rotting, fallen tree in cloud forest. Other specimens were found in humid forest leaf-litter and in the soil of a transitional forest.

Identification
Brown head, mesosoma, and gaster contrasting with yellow legs and antennae; gastral tergites I & II with a dense layer of pubescence.

Compare with: Nylanderia bibadia, Nylanderia pini, Nylanderia fuscaspecula

Workers of this species can usually be separated from N. fuscaspecula and N. pini based on the presence of dense pubescence of the first gastral tergite. Males of N. metacista males have a fine, wispy, silvery pubescence between the ocelli and the compound eyes. In contrast, N. pini has short, thick, dark brown pubescence and some pubescence free areas between the ocelli and the compound eyes. Separating N. metacista from N. bibadia can generally be done with color: N. metacista has lighter brown workers, with distinct yellow antennae and legs, which contrasts against the darker workers of N. bibadia. However, color is not always reliable and can be difficult to qualitatively assess. Nylanderia metacista is overall smaller than N. bibadia (especially with regards to head length and width).

Male morphology provides some further characters for separating the two species. Males of N. metacista are brownish-yellow whereas N. bibadia are dark brown. Additionally, in N. metacista the gastral pubescence is very appressed against the cuticle. In contrast N. bibadia possess gastral pubescence that is less appressed, the gaster having a shaggy appearance. The anteroventral process of the penial sclerites in N. metacista is distinctly emarginate in contrast to the broadly rounded anteroventral process of N. bibadia. Uniquely among West Indian Nylanderia N. bibadia, N. metacista and Nylanderia pubens have rather elongated penial sclerites. The valvurae of the penial sclerites in all three species are also ventral to the midline of the penial sclerites. It is not surprising that N. metacista and N. bibadia workers can be challenging to separate from each other because molecular analyses indicate they are sister taxa (Gotzek et al. 2012).

Distribution based on Regional Taxon Lists
Neotropical Region: Dominican Republic.

Nomenclature

 *  metacista. Nylanderia metacista LaPolla & Kallal, 2019: 422, figs. 43-51 (w.q.m.) DOMINICAN REPUBLIC.

Worker
(n=7): TL: 2.50–2.80; HW: 0.53–0.59; HL: 0.64–0.68; EL: 0.17–0.19; SL: 0.74– 0.78; WL: 0.80–0.89; GL: 0.90–1.30. SMC: 18–25; PMC: 3–6; MMC: 2. indices: CI: 83–88; REL: 25–28; SI: 132–142; SI2: 22–24.

Head: sides of head in full face view nearly parallel; posterolateral corners rounded; posterior margin straight, occasionally very slight emarginated medially; anterior clypeal margin emarginate; ocelli absent; eye well-developed. Mesosoma: in lateral view, pronotum convex; anterior margin of mesonotum raised slightly above posterior pronotal margin; metanotal area without short flat area before spiracle; dorsal face of propodeum slightly convex; dorsal face of propodeum and mesonotum approximately the same height in lateral view. Color and pilosity: body brown; mandible, scape, legs, mesocoxa and metacoxa lighter brown; cephalic pubescence sparse; pronotum, mesonotum, anterior portion of propodeum with sparse pubescence; gastral tergites I & II with dense pubescence dorsally.

Queen
(n=1): TL: 4.80; HW: 0.86; HL: 0.87; EL: 0.3; SL: 0.92; WL: 1.6; GL: 2.3. SMC: 8; PMC: 5; MMC: 27. indices: CI: 98; REL: 34; SI: 107.

Generally, as in worker with modifications expected for caste and with the following noted difference: lighter brown (to yellow) than seen in workers.

Male
(n=1): TL: 2.40; HW: 0.53; HL: 0.56; EL: 0.23; SL: 0.85; WL: 0.85; GL: 1.00. SMC: 4; PMC: 0; MMC: 8. Indices: CI: 94; REL: 41; SI: 161.

Head: sides of head in full face view nearly parallel becoming distinctly broader posterior to eyes; clypeus evenly rounded anteriorly; mandible with distinct apical tooth and much smaller subapical tooth adjacent to apical tooth; basal angle rounded and indistinct. Mesosoma: in lateral view, dorsal margin of mesoscutum same as height as dorsal margin of mesoscutellum; propodeum steeply sloping without distinct dorsal and declivitous faces. Genitalia: gonopod apex coming to triangular point in lateral view; in dorsal view, gonopod margin curves away from penial sclerite; digitus with pointed apex that bends away from penial sclerite; cuspis tubular, rounded at apex bending sharply towards digitus; anteroventral process of penial sclerite comes to a point with ventral margin of process emarginate; valvura of penial sclerite placed ventral to midline. Color and pilosity: yellow to light brown; head darker than remainder of body; head, scapes, mesosomal notum, legs and gastral dorsum with a layer of short pubescence; fine, wispy, silvery pubescence between the ocelli and the compound eyes.

Type Material
Holotype worker, DOMINICAN REPUBLIC: Cachote Forest, 18° 04.01’N, 71° 10.768’W, elev. 1054 m, cloud forest, nest under bark of rotting, fallen tree, 28.vii.2009, J.S. LaPolla & S.A. Schneider (USNM00754797). 3 paratype workers, 1 paratype male with same locality data as holotype (specimens are from the same nest as holotype) (NMNH & ).

Etymology
Species epithet is a combination of cista (L. = box) with the prefix meta- (L. = end), named for thickened tips of the penial sclerites found in this species.

References based on Global Ant Biodiversity Informatics

 * LaPolla J. S., and R. J. Kallal. 2019. Nylanderia of the World Part III: Nylanderia in the West Indies. Zootaxa 4658: 401-451.