Nylanderia usul, Williams & Williams & Lapolla & Lucky, 2025

Williams, Jason L., Williams, John F., Lapolla, John S. & Lucky, Andrea, 2025, Nylanderia of the World, Part IV: Taxonomic contributions to the American Clade I of New World Nylanderia (Hymenoptera: Formicidae), Zootaxa 5569 (3), pp. 549-593 : 584-587

Nylanderia usul , sp. nov.

Figs. 62–64 (worker); Figs. 65–66 (queen); Figs. 67–70 (male)

Holotype worker, COSTA RICA: San José, 11km SSE Santa María, 9.55301 -83.94523 ±10m,elev.1950m, 24.vi.2015, cloud forest, sifted litter, ADMAC#Wa-E-04-1-49 ( USNM: USNMENT01131798 ). 5 paratype workers, 1 paratype queen, and 1 paratype male with same locality data as holotype ( USNM: USNMENT01131109 , USNMENT01131799 , USNMENT01131800 , USNMENT01131819 , USNMENT01131831 ; MNCR: USNMENT01131802 , USNMENT01131804 ).

Worker diagnosis: Antennae relatively short, with scapes surpassing posterior margin by about a quarter to a third of their length; color variable from yellow to dark brown, with meso- and metacoxae at most somewhat lighter than mesosoma; fine cuticular microsculpture resulting in moderate to strong blue iridescence on head, mesosoma, and gaster; moderate to dense cephalic pubescence; propodeum high and evenly rounded, with posterior face steep and at most slightly longer than dorsal face.

Compare with: N. mendax , N. mosaica

WORKER. Measurements (n=11): TL: 2.00–2.35; EL: 0.11–0.13; EW: 0.08–0.10; IOD: 0.32–0.39; HE: 0.01– 0.02; HL: 0.58–0.65; HW: 0.47–0.53; HLA: 0.18–0.23; HLP: 0.27–0.30; SL: 0.65–0.74; PW: 0.36–0.40; MW: 0.18–0.21; PrW: 0.26–0.32; PDH: 0.18–0.27; PTW: 0.13–0.15; LHT: 0.58–0.69; WL: 0.69–0.80; GL: 0.70–0.94; SMC: 9–12; PMC: 2–3; MMC: 2–3. Indices: BLI: 144–154; CI: 81–84; EPI: 67–80; HTI: 113–131; REL: 18–21; SI: 128–140.

Color: variable, from yellow to dark brown; darker specimens often with yellow to yellow-brown mandibles and leg joints; in darker specimens, meso-and metacoxae somewhat lighter than mesosoma; overall cuticle moderately to finely microsculptured, resulting in moderate to strong blue iridescence on head, mesosoma, and gaster. Pilosity: moderate to dense cephalic pubescence; mesosoma pubescence sparse to absent, limited at most to scattered hairs on pronotum and propodeum, and a fringe of hairs concentrated just posterior to the metanotal groove; gaster pubescence sparse to absent; pair of small, erect setae on apex of petiole. Head: longer than broad and quadrate with distinct posterolateral corners and flattened posterior margin, with moderate medial emargination; scapes surpass posterior margin of head by about a quarter to a third of their length; median ocellus small, but often apparent; lateral ocelli absent or not apparent. Mesosoma: promesonotal area evenly convex in profile view, with posterior margin of pronotum continuous or nearly continuous with anterior margin of mesonotum; propodeum high and evenly rounded, with posterior face steep and at most slightly longer than dorsal face.

QUEEN. Measurements (n=1): TL: 3.73; EL: 0.19; HL: 0.72; HW: 0.69; SL: 0.86; WL: 1.44; GL: 1.58. Indices: BLI: 200; CI: 97; REL: 26; SI: 125.

Relatively large. Color: medium to dark brown, with meso- and metacoxae at most somewhat lighter than mesosoma. Pilosity: most of body covered in moderate to dense pubescence; pubescence sparse to absent laterally on pronotum, sparse on most of anepisternum, absent on dorsal half of katepisternum. and absent on posterior face of propodeum; 4-5 small, erect setae on anepisternum.

MALE. Measurements (n=1): TL: 2.20; EL: 0.18; HL: 0.53; HW: 0.46; SL: 0.70; WL: 0.82; GL: 0.85. Indices: BLI: 180; CI: 86; REL: 34; SI: 154.

Color: medium brown with yellow mandibles; meso- and metacoxae lighter than mesosoma. Pilosity: dense pubescence on head, mesoscutum, and mesoscutellum; pubescence sparse to absent on pronotum, anepisternum, katepisternum, propodeum, and gaster; 1-2 small, erect setae on anepisternum. Head: as broad as long; compound eyes surpass lateral margins of head in full-face view; scapes curve sinuously and surpass posterior margin of head by about a third of their length. Mesosoma: In profile view, propodeum gently curved with dorsal face somewhat longer than posterior face. Genitalia: gonopod long, narrow, and evenly triangular to weakly digitiform, with apex tapered and coming to a point ( Fig. 71 ); in ventral view, ventromedial edge of basivolsella unevenly bracket-shaped and crenate, with edge at base of cuspis forming a right angle ( Fig. 69 ); gonossiculus straight and nearly three times longer than cuspis.

Other material examined: COSTA RICA: Heredia, 16km SSE La Virgen , 10.26667 -84.08333 ±m, elev. 1100m, 8.ii.2001, montane wet forest, leaf litter,ALAS#11/B/all; Heredia, 16km SSE La Virgen , 10.26863 -84.08287 ± 200m, elev. 1110m, 14.iii.2001, montane wet forest, leaf litter, ALAS#11/WF/02; Heredia, 16km SSE La Virgen , 10.26863 -84.08287 ± 200m, elev. 1110m, 14.iii.2001, montane wet forest, leaf litter, ALAS#15/WF/02; Puntarenas, Monteverde , 10.30327 -84.81099 ± 50m, elev. 1400m, 6.i.2020, moist forest, leaf litter, J.T. Longino #JTL10993-s; Puntarenas, Monteverde , 10.30259 -84.79269 ± 50m, elev. 1590m, 13.v.2014, cloud forest, leaf litter, J.T. Longino #JTL8625-s; Puntarenas, Monteverde , 10.28987 -84.79322 ± 50m, elev. 1310m, 13.v.2014, moist forest, leaf litter, J.T. Longino #JTL8631-s; Puntarenas, Monteverde , 10.28744 -84.79266 ± 50m, elev. 1180m, 13.v.2014, moist forest, leaf litter, J.T. Longino #JTL8632-s; Alajuela, 5km E Monteverde , 10.29824 -84.78163 ± 50m, elev. 1495m, 18.v.2014, cloud forest, leaf litter, J.T. Longino #JTL8698-s; San José, 7.5km SSE Santa Maria de Dota , 9.58689 - 83.94758 ± 50m, elev. 1520m, 27.v.2014, 2nd growth cloud forest, leaf litter, T. Sumnicht & J.T. Longino #JTL8704- s; San José, 11km SSE Santa María , 9.55387 -83.94547 ± 10m, elev. 1940m, 24.vi.2015, cloud forest, leaf litter, ADMAC#Wa-E-04-1-21; San José, 11km SSE Santa María , 9.55378 -83.94551 ± 10m, elev. 1940m, 24.vi.2015, cloud forest, leaf litter, ADMAC#Wa-E-04-1-24; San José, 11km SSE Santa María , 9.55296 -83.94551 ± 10m, elev. 1940m, 24.vi.2015, cloud forest, leaf litter, ADMAC#Wa-E-04-1-42; San José, 8km SSE Santa María , 9.58425 -83.94826 ± 20m, elev. 1580m, 23.vi.2015, cloud forest, leaf litter, ADMAC#Wm-E-04-1-02; San José, 8km SSE Santa María , 9.57877 -83.95085 ± 20m, elev. 1620m, 25.vi.2015, cloud forest, leaf litter, ADMAC#Wm-E-04-1- 06; San José, 9km SSE Santa María , 9.56191 -83.94807 ± 20m, elev. 1830m, 25.vi.2015, cloud forest, leaf litter, ADMAC#Wm-E-04-1-09; San José, 10km SSE Santa María , 9.55908 -83.94646 ± 20m, elev. 1870m, 25.vi.2015, cloud forest, leaf litter, ADMAC#Wm-E-04-1-10.

Etymology: The species epithet is derived from Frank Herbert’s science fiction novel Dune. In the novel, “Usul” is the secret name given to the protagonist, Paul Atreides, by the Fremen, the desert dwellers of the planet Arrakis. This name references the species’ moderate to intense blue iridescence, alluding to the “blue-within-blue” eyes that Paul acquires after joining the Fremen and consuming the spice melange. The term “Usul” translates to “the strength of the base of the pillar” and is derived from the Arabic word usul , the plural form of asl, which means “origin,” “root,” or “principle.”

Notes: Nylanderia usul workers most strongly resemble those of N. mendax and N. mosaica . This species is most readily separable from N. mendax by its relatively short scapes, which only surpass the posterior margin of the head by a quarter to a third of their length, whereas in N. mendax they surpass the posterior margin by nearly half their length. There are two distinct color morphs of this species. The dark form is dark brown with yellow to yellow-brown mandibles and tarsi, meso- and metacoxae somewhat lighter than the mesosoma, and has moderate cephalic pubescence, concentrated mostly as patches around the compound eyes ( Fig. 4B ). The light form is uniformly yellow, with dense cephalic pubescence ( Fig. 4A ). The light form is more likely to be confused with N. mosaica , but the latter is smaller in overall size and bicolored with a yellow to yellow-brown head and mesosoma and medium to dark brown gaster. Interestingly, the light form, represented by NT002, NT003, NT020, and NT024 in the phylogeny ( Fig. 3 ), resolved as paraphyletic with respect to the dark form. This pattern may indicate a case of incipient speciation, in which one is beginning to diverge from the other but has not yet achieved full reproductive isolation. Consequently, the two forms may be interpretable as two distinct species based on their morphology. However, for now we conservatively treat them all as a single species. If someday these two forms are split into separate species, the dark form will keep the name N. usul and the light form will take a new name. Nylanderia usul is only known from moderate to high elevation forests in Costa Rica ( Fig. 2B ), where it is sympatric with only N. mosaica and no other species in American Clade I.

Figures

FIGURE 2. Distributions of species: (A) N. austroccidua in the United States and northern Mexico, (B) species found across southern Mexico and Mesoamerica, and (C) N. docilis in South America. Maps were created using GPS coordinates listed in Table S1 and from the Global Ant Biodiversity Informatics (GABI; Guénard et al. 2017) database.

FIGURE 3. Maximum likelihood phylogeny of clade AC1 reconstructed using the 90% complete SWSC partitioned matrix. Nodal support (SH-aLRT/UFBoot) is displayed only for nodes with <95% support for either measure. The map inset in the bottom-right indicates the extent of geographical overlap between the Nearctic and Neotropical subclades around the Isthmus of Tehuantepec.

FIGURE 4. Line drawings depicting examples of cephalic pubescence patterns in full-face view: (A) N. austroccidua with uniformly dense cephalic pubescence; (B) N. lazulina with moderate pubescence, concentrated primarily in areas anterior and posterior to the compound eyes; and (C) N. cf. docilis with sparse cephalic pubescence.

FIGURE 71. Line drawings of male gonopods of N. austroccidua, N. breviscapa, N. contraria, N. cf. docilis, N. lazulina, and N. usul.

FIGURES 62–64. Nylanderia usul holotype worker (USNMENT01131798). Lateral, full-face, and dorsal view of the body.

FIGURES 65–66. Nylanderia usul paratype queen (USNMENT01131819). Full-face and lateral view of the body.

FIGURES 67–70. Nylanderia usul paratype male (USNMENT01131831). Full-face and lateral view of the body; ventral and dorsal view of the genital capsule.