Xymmer muticus ( Santschi, 1914 )

Hamer, Matthew T., Gómez, Kiko & Jocque, Merlijn, 2025, A new Xymmer Santschi, 1914 (Formicidae: Amblyoponinae) species from the Congo Basin, with male and female descriptions of X. muticus (Santschi, 1914), Zootaxa 5647 (5), pp. 479-495 : 481-489

Xymmer muticus ( Santschi, 1914)

Figure 1A–C ; 2A–C ; 3A–C ; 4A–E .

Stigmatomma (Xymmer) muticum Santschi, 1914 d: 311 , fig. 2 (w.) NIGERIA. (specimen images examined)

Combination in Xymmer : Wheeler, 1922: 758. In Amblyopone : Brown, 1960 a: 168. In Xymmer : Yoshimura & Fisher, 2012 a: 19.

Redescription—worker

Figures 1A–C .

Material examined (n = 14):

Ivory Coast: Montagnes: Site 07 (Taï N. P.) 200 m, 5.84598, -7.34815, Primary Forest. Gómez, K., Kouakou, L. 13/11/2019, Hand, ex. rotten log; 1 worker on pin KGCOL03192, RBINSFOR1000801 [RBINS] • same data; 1 worker on pin KGCOL03959, RBINSFOR1000804 [RBINS] • same data; 1 worker on pin KGCOL03960, RBINSFOR1000805 [RBINS] • Site 07 (Taï N. P.) 200 m, 5.84598, -7.34815, Primary Forest. Gómez, K., Kouakou, L. 13/11/2019, Hand, ex. rotten log; 1 worker in ethanol KG04106, 2 workers on pin KGCOL03165 [KGAC] • Ivory Coast: Montagnes: Site 04 (Taï N. P.) 200 m, 5.83093, -7.344, Primary Forest. Gómez, K., Kouakou, L. 10/11/2019, Hand, Ex soil; 1 worker in ethanol KG04078, 1 worker on pin KGCOL03166 [KGAC] • same data; 2 workers on pin KGCOL03165 [KGAC] • Site 07 (Taï N. P.) 200 m, 5.84598, -7.34815, Primary Forest. Gómez, K., Kouakou, L. 13/11/2019, Hand, ex. rotten log; 2 workers in ethanol KG04341 [KGAC] • Ivory Coast: Oumé-Goulikao, Foret. Kone, M. 31/03/2009, M1 (0-15 cm); 1 worker on pin, RBINSFOR002633 [RBINS] • same data, Winkler, Leaf litter, 1 worker on pin, KGCOL03166 [KGAC].

Measurements (n = 3):

HW 0.51–0.52; HW₂ 0.49–0.51; HL 0.57–0.59; MBL 0.36–0.36; SL 0.35–0.40; WL 0.82–0.83; ML 0.79–0.81; PNW 0.27–0.34; HFL 0.38–0.39; PL 0.41–0.42; PH 0.27–0.28; DPW 0.22–0.27; DPL 0.27–0.30; AIIIW 0.35–0.35; AIVW 0.35–0.38; AIIIL 0.24–0.28; AIVL 0.28–0.29; AVL 0.11–0.15; AVIL 0.07–0.10; AVIIL 0.17–0.26; TL 3.08– 3.20.

Indices: CI 86.50–90.01; MI 69.13–71.54; SI 68.45–79.25; WI 241.54–302.63; HFI 72.72–77.67; AIIII 130.74– 161.86.

Head

In full-face view, head slightly longer than broad, subquadrate (CI 86.50–90.01); lateral head margins convex, reaching maximum width in anterior half; occipital margin weakly concave. Mandible linear, long (MI 69.13–71.54), widest medially; masticatory margin with 9 teeth, 5 of them being paired; first two basal teeth minute, unpaired; proceeding 5 teeth paired, triangular, subtly incrassate apically; subapical tooth unpaired, triangular; apical tooth large, sharply triangular. Eye absent. Anteromedial clypeal lobe, projecting into intermandibular space, straight to very subtly concave, lacking denticles. Frontal lobes concealing majority of antennal foramen. Frontal carinae minute, scrobes absent. Genal teeth absent. Scape failing to reach posterior head margin (SI 68.45–79.25), reaching its maximum width slightly apically to the mid-length. Antennal pedicel longer than wide, reaching maximum width apically; flagella segments I-IX wider than long and incrassate apically; flagella segment X longer than wides sharppointed apically.

Mesosoma

In profile view, dorsal outline gradually convex, highest at promesonotal articulation; posterior pronotal angle obtuse, propodeal dorsum gradually sloping towards declivity. In dorsal view, pronotum just slightly wider than propodeum; mesosoma narrowest at mesonotum and anterior region of propodeum; pronotal anterior margin convex, posterior margin concave; promesonotal articulation present, metanotal groove absent; propodeal declivity flat. In lateral view, lower propodeal lobes present. Lower-upper mesopleural suture absent; meso-metapleural suture present only between the lower portion of these sclerites. Anterolateral corner of the mesopleuron with a short blunt, anteriorly directly cuticular extension. Metapleural gland reservoir circular, occupying less than half of propodeal surface, located on the lower and posteriormost corner of propodeum in lateral view; propodeal spiracle circular, located below the median line of propodeum, separated from the reservoir by a distance about 1× its diameter. Propodeal lobe inconspicuous, semi-circular. Meso-metapleural suture present only between the lower portion of these sclerites. Profemora medially swollen. Tibiae roughly triangular, distinctly wider apically than at base. Metatibiae with pectinate comb and barbulate spur; mesotibiae with one spur. Pretarsal claws simple, lacking teeth on their inner margins.

Metasoma

In lateral view, petiole with distinct peduncle; anterior face straight; angle between petiole anterior face and dorsum obtuse; dorsum subtly convex across length; lacking posterior face. Posteroventral angle obtuse; anteroventral margin subtly concave, as long as posteroventral margin. Petiole spiracle circular; located just posterior to peduncle. In dorsal view, petiole narrow, distinctly longer than wide, lateral margins subtly convex.Anterolateral angle gradually curved. In ventral view, petiolar poststernite ovoid; narrow inverted U-shaped sulcus separating poststernite and laterotergite; ventrolateral junction marginated. In profile, ventral outline of gastral sternite of abdominal segment III distinctly more convex than corresponding tergite. Girdling constriction of abdominal segment IV conspicuous. Sting well-developed.

Sculpture

Head densely foveolate overall, with medial smooth central, longitudinal strip extending from clypeal lobes to vertexal margin. Mandible, scape and antennal segments punctulate, rendering a dull surface. Pronotum overall punctulated, mat, except for collar, with faint transverse strigulae, mesopleuron, metapleuron and propodeum including declivity finely striate. Visible portion of presternite III imbricate. Girdling constriction abdominal segment IV with areolate sculpturing across its width. Abdominal segments II-VII finely punctured with smooth and shining interspaces.

Pilosity

Whole body covered with appressed dense pubescence. Mandible masticatory margin lined with a series of erect, fine setae directed into inner mandibular space; mandible dorsum with subdecumbent setae of varying length. Anterior clypeal margin with a pair of long and numerous fine shorter setae that extend well into inter-mandibular space. Head dorsum, with pubescence directed medially. Frontal lobes with numerous, appressed setae radiating outwards. Meso-, metapleuron and declivity of propodeum mostly glabrous. Petiole peduncle glabrous. Gastral sternites with numerous, short subdecumbent setae as well as longer, erect setae; pygidium and hypopygium with a denser concentration of such setae, including the longest in metasoma, lacking spiniform setae. Legs covered with appressed pubescence.

Colour

Head, mesosoma, and metasoma orange yellow; mandible, scape, flagellum, and legs yellow.

Description—gyne

Figures 2A–C ; 4B

Material examined (n = 4):

Ivory Coast: Montagnes: Site 07 (Taï N. P.) 200 m, 5.84598, -7.34815, Primary Forest. Gómez, K., Kouakou, L. 13/11/2019, Hand, ex. rotten log; 1 alate gyne on pin, KGCOL03193, RBINSFOR1000802 [RBINS] • same data; 1 dealate gyne in ethanol, KG04106 [KGAC] • Site 02 (Taï N. P.) 200 m, 5.83117, -7.3429, Primary Forest. Gómez, K., Kouakou, L. 08/11/2019, Winkler, Leaf litter; 1 dealate gyne on pin, KGCOL00224 [KGAC] • Site 06 (Taï N. P.) 200 m, 5.83458, -7.34638, Primary Forest. Gómez, K., Kouakou, L. 12/11/2019, Winkler, Leaf litter; 1 dealate gyne on pin KGCOL00282 [KGAC].

Measurements (n = 1):

HW 0.55; HW₂ 0.54; HL 0.60; MBL 0.38; SL 0.37; WL 0.93; ML 0.89; PNW 0.38; HFL 0.42; PL 0.45; PH 0.30; DPW 0.25; DPL 0.30; AIIIW 0.41; AIVW 0.43; AIIIL 0.34; AIVL 0.37; AVL 0.20; AVIL 0.18; AVIIL 0.26; TL 3.71.

Indices: CI 92.17; MI 69.44; SI 66.00; WI 237.77; HFI 75.59; AIIII 164.92.

Head

As in the worker, except: in full face view, eye present in posterior third of head; eye positioned laterally; with ca. 30 ommatidia and 7 across maximum width; eye barely surpassing lateral head margin. Ocelli present in posterior quarter of head, their width shorter than the distance between them. Masticatory margin of mandible with a maximum 8 teeth, 5 paired.

Mesosoma

With the usual gyne morphological features; mesosoma segmented, in dorsal view, pronotum visible; mesoscutum wider than long; notaular lines absent; parapsidal lines present, faintly impressed; scuto-scutellar suture present, narrow; metanotum present as a transverse strip, longer than wide; mesepimeral lobe indistinct; meso-metapleural sulcus narrow; metapleuron divided into upper metapleuron only, lower metapleuron fused to lateral propodeal surface. Metapleural gland reservoir large, almost reaching propodeal spiracle.

Metasoma

As in the worker, but metasomal segments III-VII enlarged.

Wings

Forewing; as in Figure 10. and Xymmer forewing description presented in Yoshimura and Fisher (2012). Hindwing; as in Figure 10. and Xymmer hindwing description presented in Yoshimura and Fisher (2012).

Sculpture

As in worker, except: mesoscutum and metanotum smooth and shining other than hair bearing punctures; meso-, meta- pleuron, and lateral face of propodeum with stronger striae covering the majority of each pleuron.

Pilosity

As in worker except for denser pubescence.

Colour

Head, mesosoma, metasoma, mandible, scape, flagellum, and legs light orange yellow.

Description–male

Figures 3A–C ; 4C–E

Material examined (n = 4):

Ivory Coast: Montagnes: Site 07 (Taï N. P.) 200 m, 5.84598, -7.34815, Primary Forest. Gómez, K., Kouakou, L. 13/11/2019, Hand, ex. rotten log; 1 male on pin, KGCOL03192, RBINSFOR1000803 [RBINS] • Site 07 (Taï N. P.) 200 m, 5.84598, -7.34815, Primary Forest. Gómez, K., Kouakou, L. 13/11/2019, Hand, ex. rotten log; 3 males in ethanol, KG04106 [KGAC].

Measurements (n = 1):

HW 0.45; HW₂ 0.31; HL 0.49; MBL 0.20; SL 0.12; WL 0.92; ML 0.94; PNW 0.52; HFL 0.43; PL 0.36; PH 0.26; DPW 0.21; DPL 0.18; AIIIW 0.29; AIVW 0.324; AIIIL 0.20; AIVL 0.20; AVL 0.20; AVIL 0.17; AVIIL 0.15; AVIIIL 0.11; TL 2.99.

Indices: CI 91.08; MI 43.43; SI 26.50; WI 180.27; HFI 95.55; AIIII 135.38.

Head

In full-face view, head longer than broad (excluding eyes); posterior margin straight, posterolateral margins evenly curving towards posterior margin. Mandibles linear and subtly falcate, bearing a single apical tooth. Anterior clypeal margin straight, posterior clypeal margin concave between antennal sockets. Frontal lobes and carinae absent. Frontal furrow present, feebly impressed and terminating in posterior third of head. Ocelli subequal in size, located at the posterior quarter of head, separated from each other by a distance greater than their diameters, subtly protruding from posterior head margin. Eye occupying majority of lateral head margin; significantly protruding; with ca. 100 ommatidia. Antennae comprising scape, pedicle and 11 flagellomeres; scape shorter than mandible, about 1.5× as long as pedicel; pedicle as long as wide; flagellomeres longer than broad, 2nd flagellomere as long as pedicel, 11th flagellomere as long as scape. Palp formula indiscernible.

Mesosoma

In dorsal view, pronotum barely visible; mesoscutum subtly wider than long. Notauli strongly impressed; meeting medially, forming a Y-shaped sulcus; anteriorly extending to lateral mesoscutal margins, posteriorly reaching scutoscutellar sulcus. Parasidal line weakly impressed on mesoscutal posterior half. Mesoscutellum as wide as long. Scutoscutellar suture deeply impressed. Metanotum a thin transverse strip. In lateral view, mesopleural sulcus absent. Mesepimeral lobe not distinct. Mesopleuron not divided. Upper and lower metapleuron divided by a sulcus; lower metapleuron well-separated from lateral propodeum by a sulcus. Propodeal spiracle round, located just below medial line of propodeum. Propodeum dorsum as long as declivity, angle of junction obtuse.

Wings

Fore and hindwings as in Figure 10 and Xymmer description presented in Yoshimura and Fisher (2012).

Metasoma

In lateral view, petiole rhomboidal in shape, slanted posteriorly. Posterior margin fully fused to metasomal segment III. In lateral view, peduncle small; subpetiolar process absent. In dorsal view, petiolar dorsum as wide as long, lateral margins straight to feebly convex. In ventral view, prosternite present as a large anteriorly convex and expanding posteriorly. Cinctus not well marked. Abdominal sternum IX narrowly convex. Parameres long, laterally convex and apically blunt. Digitus and aedeagus as long as parameres.

Sculpture

Head dorsum densely foveolate; laterally smooth and shining with scattered punctae. Clypeal dorsum areolaterugose. Mandible smooth and shining. Pronotum smooth and shining. Mesoscutum and Mesoscutellum densely foveolate; mesoscutum posterolaterally with scattered punctae; notauli and scutoscutellar sulcus scrobiculate. Metanotum, propodeum, and petiolar peduncle densely punctate. Mesopleuron and upper metapleuron smooth and shining; lower metapleuron faintly striated on its upper section and faintly punctate on its lower section, otherwise smooth and shining. All leg segments smooth and shining. Petiole dorsum thinly foveolate, laterally smooth and shining. Abdominal segments III–VIII smooth and shining with scattered punctae. Girdling constriction weakly areolate.

Pilosity

Head dorsum with dense, short, subdecumbent setae. Clypeal dorsum and anterior clypeal margin with sparse, decumbent setae. Mandible dorsum with longer, erect setae. Scape and flagellum with subdecumbent, appressed and scarce erect setae. Eye with short, erect setae between ommatidia. Mesosoma dorsum with dense, subdecumbent setae; laterally mostly glabrous; scattered subdecumbent hairs on lower mesopleuron. Petiole and abdominal segments III-VII with appressed and subdecumbent hairs; lateral surface of petiole mostly glabrous. Abdominal sternite IX with numerous long setae that extend beyond posteriormost margin. Parameres with several short, erect setae laterally.

Colour

Head, mesosoma, metasoma brown; mandibles and scape light brown fading into orange; pedicle yellow; legs light brown.

Bionomics

All X. muticus specimens examined within this study were collected from primary forests from within leaf litter and from decaying wood. Other specimens on antweb.org are known from primary evergreen rainforests (e.g. CASENT0351684), littoral rainforests (e.g. CASENT0500007), as well as savannah ecosystems (e.g. CASENT0006826), collected from within rotting wood, leaf litter and soil microhabitats.

Figures

FIGURE 1. Xymmer muticus worker (RBINFOR1000801). A) Lateral view, B) Full face view, C) Dorsal view.

FIGURE 2. Xymmer muticus alate gyne (RBINFOR1000802). A) Lateral view, B) Full face view, C) Dorsal view.

FIGURE 3. Xymmer muticus male (RBINFOR1000803). A) Lateral view, B) Full face view, C) Dorsal view.

FIGURE 4. Close up images of Xymmer muticus worker (RBINFOR1000801), alate gyne (RBINFOR1000802) and male (RBINFOR1000803) morphological features. A) Alate gyne wings, B) Mandibles and lower head region in full face view, C) Male wings, D) Male genital capsule dorsal, E) Male genital capsule ventral.