Pseudomyrmex nimbus

Pseudomyrmex nimbus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Pseudomyrmecinae
Genus:	Pseudomyrmex
Species group:	elongatulus
Species:	P. nimbus
Binomial name
Pseudomyrmex nimbus Ward & Branstetter, 2022

Pseudomyrmex nimbus is known only from several cloud forest sites in Costa Rica, at elevations of 730 m to 1,200 m. The following are Jack Longino’s field notes on the type series (JTL2694): ‘Workers abundant on small Inga sapling. I dissected the entire tree, finding 3 nests excavated in live stems (there was also stem-borer damage here and there, so the ants could have been invading pre-existing cavities). I never found reproductives. Either the queen was little different from workers and escaped, or the colony was queenless, or there was more of the colony off the Inga tree.’ Another nest series (JTL/5Jul84/1017) was collected ‘inside branch of still live but recently felled Inga’ and included workers, alate queens, and a male. A third collection by Longino (JTL0900) was taken in a live Cecropia insignis sapling. Thus, the available data suggests that this species is a live-stem nester, a habit not seen in the majority of Pseudomyrmex species (Ward 1991). There is no evidence that P. nimbus keeps trophobionts (hemipterans) in these nests.

Identification

Relatively large species (HW 1.03–1.20, LHT 0.96–1.09); head only moderately elongate (CI 0.85–0.89) and with rounded posterolateral corners in full-face view (Fig. 16); eyes relatively large (REL 0.48–0.51); frontal carinae separated by less than basal scape width; metanotal groove strongly impressed, conspicuous in profile; dorsal face of propodeum generally convex in profile, rounding into declivitous face, the two subequal in length; petiole slender, elongate-triangular in profile (PLI 0.44-0.53, PL/ HL 0.58–0.60, PL/LHT 0.71–0.79); petiole with slight anterior peduncle, in profile the anterodorsal face flat to convex, ascending gradually to summit in posterior third of node, then rounding into more steeply descending posterior face; profemur relatively slender (FI 0.41–0.45); hind leg relatively long (LHT/HL 0.76–0.82). Head subopaque, densely punctulate-coriarious, the punctures becoming less dense on vertex (separated by their diameters or more). Standing pilosity sparse, absent from propodeum and mesonotum (MSC 2–5). Head, dorsum of propodeum, metafemur, and gaster dark brown, other parts of body with variably lighter coloration (medium brown to yellow-brown).

Pseudomyrmex nimbus can be recognized by the combination of large size (worker HW 1.03–1.20; queen HW 1.15–1.18), well-developed metanotal groove (in worker), and predominantly dark coloration. The relatively long legs (worker LHT/HL 0.76–0.82, queen LHT/HL 0.70–0.72) and elongate eyes (worker REL 0.48–0.51; queen REL 0.48) are also notable. This species is in the P. elongatulus complex (within the P. elongatulus group), and is a distant sister to the trio of Pseudomyrmex exoratus, Pseudomyrmex elongatulus, and Pseudomyrmex ereptor (Fig. 1).

Keys including this Species

• Key to Pseudomyrmex elongatulus group species

Distribution

Latitudinal Distribution Pattern

Latitudinal Range: 10° to 9°.

North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

• Source: Ward & Branstetter, 2022

Distribution based on Regional Taxon Lists

Neotropical Region: Costa Rica.

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Phylogeny

Relationships among Pseudomyrmex elongatulus group species based on Ward & Branstetter (2022).

Pseudomyrmex	Pseudomyrmex salvini some Pseudomyrmex championi some Pseudomyrmex championi Pseudomyrmex apache Pseudomyrmex fasciatus some Pseudomyrmex cognatus some Pseudomyrmex cognatus Pseudomyrmex comitator some Pseudomyrmex arcanus some Pseudomyrmex arcanus Pseudomyrmex capillatus Pseudomyrmex veracruzensis Pseudomyrmex nimbus Pseudomyrmex exoratus Pseudomyrmex ereptor Pseudomyrmex elongatulus

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• nimbus. Pseudomyrmex nimbus Ward & Branstetter, 2022: 25, figs. 16, 26 (w.) COSTA RICA.

Type Material

• Worker. COSTA RICA Alajuela: Río Peñas Blancas, 800 m, 10° 19′ N, 84° 43′W, 22–25 May 1990, ex live stems Inga sapling, wet forest clearing, J. Longino JTL2694 (MUCR) (CASENT0863541).
• Paratypes: series of workers, same data as holotype (CASC, JTLC, LACM, MCZC, PSWC, UCDC, UNAM, USNM).

References

• Ward, P.S., Branstetter, M.G. 2022. Species paraphyly and social parasitism: Phylogenomics, morphology, and geography clarify the evolution of the Pseudomyrmex elongatulus group (Hymenoptera: Formicidae), a Mesoamerican ant clade. Insect Systematics and Diversity 6(1), 4: 1-31 (doi:10.1093/isd/ixab025).