Nylanderia caerula

A ground nesting species that has been found across a range of habitats from dry scrub to humid forest.

Identification
Dark brown mesosoma with distinct blue iridescence seen in lateral view under light microscopy on mesopleuron and sides of head and gaster; antenna, mandible and legs distinctly lighter brownish-yellow to yellow, contrasting sharply with dark brown body; gastral tergites I & II with dense pubescence.

Compare with: Nylanderia fuscaspecula, Nylanderia metacista, Nylanderia pini

Nylanderia caerula workers are most similar to workers of N. fuscaspecula, N. metacista and N. pini. This species is unique in that under light microscopy you can see distinct blue iridescence on the cuticle especially on the mesopleuron, anterolateral portions of the head and the dorsal areas of the first and second gastral tergites. It is important to note that the specimen must be in lateral view and the angle of the specimen may need to be adjusted to easily see the iridescence; otherwise it could be missed. The blue iridescence of N. caerula is reliably separates it from N. fuscaspecula, N. metacista and N. pini. The blue iridescence is interesting because it is reminiscent of what is commonly seen in workers of the Old World genus Paraparatrechina (LaPolla et al., 2010). Occasionally faint blue iridescence is seen in N. fuscaspecula, but it is not nearly as intense as in N. caerula. If this occurs separating N. fuscaspecula from N. caerula is relatively straightforward because the former typically has no gastral pubescence. Nylanderia fuscaspecula also has very sparse pubescence on the mesosoma and head in contrast to the more pubescent mesosoma and head of N. caerula.

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

Nomenclature

 *  caerula. Nylanderia caerula LaPolla & Kallal, 2019: 411, figs. 11-13 (w.) DOMINICAN REPUBLIC.

Worker
(n=8): TL: 2.30–2.50; HW: 0.51–0.56; HL: 0.61–0.68; EL: 0.16–0.19; SL: 0.80– 0.84; WL: 0.78–0.85; GL: 0.78–1.00; SMC: 23–33 PMC: 2–5; MMC: 2–3. indices: CI: 79–84; REL: 25–28; SI: 150–159; SI2: 19–23.

Head: sides of head in full face view rounded and slightly convergent anteriorly; posterolateral corner rounded; posterior margin straight and slightly emarginate medially; anterior clypeal margin slightly emarginate; ocelli absent; eye well-developed. Mesosoma: in lateral view, pronotum subangular; anterior margin of mesonotum raised slightly above posterior pronotal margin; metanotal area with short flat area anterior to spiracle; dorsal face of propodeum distinctly convex; dorsal face of propodeum and mesonotum approximately the same height in lateral view. Color and pilosity: body and procoxa dark brown, antenna, mandible, legs, and petiole yellow to brownish-yellow; in lateral view, under light microscope, blue iridescence seen on cuticle, particularly on the mesopleuron; cuticle smooth and shiny; cephalic pubescence sparse; pubescence on pronotum, mesonotum and anterior portion of propodeum; gastral tergites I & II with dense pubescence.

Type Material
Holotype worker, DOMINICAN REPUBLIC: Parque Nacional Sierra de Baharuco, 18° 18.579’N, 71° 34.668’W, elev. 407 m, humid woodland near stream, under rotten log in thick leaf litter, 25.vii.2009, J.S. LaPolla & S.A. Schneider (USNMENT00754780) ; 1 paratype worker with same locality data as holotype (specimen is from the same nest as holotype); 5 paratype workers, DOMINICAN REPUBLIC: Parque Nacional Sierra de Baharuco, 18° 17.868’N, 71° 34.144’W, elev. 722 m, mountain dry scrub forest, 25.vii.2009, J.S. LaPolla & S.A. Schneider (NMNH & ).

Etymology
The species epithet is a variation of caelum (L. = sky blue), named for this species’ bluish iridescence.

Determination Clarifications
This species is included in the phylogeny of Gotzek et. al (2012) as Nylanderia n.sp. 1 DR.

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.