Tapinoma melanocephalum ( Fabricius, 1793 )

Guerrero, Roberto J., 2018, Taxonomic identity of the ghost ant, Tapinoma melanocephalum (Fabricius, 1793) (Formicidae: Dolichoderinae), Zootaxa 4410 (3), pp. 497-510 : 499-506

Tapinoma melanocephalum ( Fabricius, 1793)

Figs. 1–28

Neotype worker ( Figs 1–3, 10 ), by present designation. Colombia: Magdalena, Santa Marta, Calabazo, roadside to Pueblito-PNN Tayrona , nest in dead branch on the roadside, secondary dry forest (11.2825°N, - 74.0239°W), 22.i.2017, leg. R. Guerrero, nest series, RJG01286 (ICNC-093716). Paraneotype workers (10), dealate queens (2), males (2), same data as neotype (1w, BMNH; 1w, 1dq, 1m CAS; 1w, 1q, ICNC; 2w, MCZ; 1w, MHNG; 2w, 1m, MZSP; 2w, USNM).

Formica melanocephala Fabricius, 1793:353 .

Lasius melanocephalus: Fabricius, 1804:417 .

Myrmica melanocephala: Lepeletier, 1836:185 .

Formica nana Jerdon, 1851:125 . Syntype worker: India: Mysore. Name pre-occupied by Latreille, 1802:263. Synonymy by Emery, 1892:166.

Myrmica pellucida F. Smith, 1857:71 . Syntype workers: Singapore ( BMNH; OXUM, University Museum of Natural History , Oxford , United Kingdom) [not examined]. Two syntype workers imaged on AntWeb: CASENT0903062 ( BMNH), CASENT0901925 ( OXUM). Synonymy by Mayr, 1886:359.

Formica familiaris F. Smith, 1860b:96 . Syntype worker: Indonesia: Bacan Island. Synonymy by Forel, 1899:101. Junior homonym of Formica familiaris F. Smith, 1860a:68 . Replacement name Formica wallacei , new name.

Tapinoma melanocephalum: Mayr, 1862:651 ; Emery, 1887:249 (male); Forel 1891:102 (description of queen); Forel, 1895:472 (re-description of worker); Kempf, 1972:247; Shattuck, 1994:148; Bolton et al. 2007: digital media (CD); Bolton, 2017: e-catalog (www.antcat.org).

Micromyrma melanocephala: Roger 1862:258 (queen, combination in Micromyrma ).

Tapinoma (Micromyrma) melanocephalum: Wheeler, 1922:923 .

Tapinoma melanocephalum var. coronatum Forel, 1908: 62 . Lectotype worker ( Figs 4–6, 11 ), by present designation: Costa Rica: Puntarenas (middle specimen on the pin, MNHG, AntWeb image and specimen identifier CASENT0909775) [examined]; two paralectotype workers: upper and lower specimen on the same pin as the lectotype. Kempf, 1972:247; Shattuck, 1994:148; Bolton et al. 2007: digital media (CD); Bolton, 2017: e-catalog (www.antcat.org). New Synonym.

Tapinoma melanocephalum var. malesianum Forel, 1913:93 . Lectotype worker ( Figs 7–9, 12 ), by present designation: Indonesia: Sumatra, Soengei Bamban (MNHG, AntWeb image and specimen identifier CASENT0909776) [examined]; paralectotypes: same data as lectotype (45 workers, 6 queens in MNHG, 1 worker in NHMB). Shattuck, 1994:148; Bolton et al. 2007: digital media (CD); Bolton, 2017: e-catalog (www.antcat.org). New Synonym.

Tapinoma (Micromyrma) melanocephalum var. australis Sanstchi, 1928a:53 . Syntypes (23 workers), Vanuatu: Santo Island, Hog Harbour (BMNH, Natural History Museum, London, U. K; NHMB, Natural History Museum, Basel, Switzerland) [not examined]. Two syntype workers imaged on AntWeb: CASENT0903063 (BMNH), CASENT0911572 (NHBM). Synonymy by Wilson & Taylor, 1967:80. Bolton et al. 2007: digital media (CD); Bolton, 2017: e-catalog (www.antcat.org). Although it appears Santschi intended australe to be the primary description and australis a redescription, australis was published first and has priority.

Tapinoma (Micromyrma) melanocephalum var. australe Santschi, 1928b:475 . Redescription and an incorrect spelling of australis . Shattuck, 1994:148; Bolton et al. 2007: digital media (CD); Bolton, 2017: e-catalog. (www.antcat.org).

Neoclystopsenella luffae Kurian, 1955:133 . Holotype male (described as a Bethylidae ): India: Delhi, Kapoor Coll., 2-7-1938, on Luffa, Imperial Entomologist (type material lost). New Synonym.

Tapinoma luffae: Brown, 1988:337 ; Shattuck, 1994:140; Bolton & al 2007: digital media (CD); Bolton, 2017: ecatalog (www.antcat.org).

Neotype measurement: HL: 0.51 mm, HW: 0.45 mm, SL: 0.47 mm; WL: 0.44 mm; CI: 88; SI: 92.

Worker measurements (n= 316): HL: 0.46 (0.38–0.60) mm, HW: 0.41 (0.35–0.60) mm, SL: 0.43 (0.35–0.52) mm; WL: 0.39 (0.28–0.60) mm; CI: 89 (80–104); SI: 94 (82–105).

Worker diagnosis. Bicolored small ants, with head and mesosoma black to brown, mandibles, antennae, legs and gaster light brown to pale yellow; third and fourth segment of the maxillary palps broad and flattened, spatulalike; basal end of the fifth segment inserted into the ventral face of the fourth segment.

Worker description ( Figs 13–14 ): Head. Ovoid, longer than wide with slightly convex lateral margins; posterior margin variable, convex to straight, or sometimes slightly emarginated medially, in all cases, with rounded posterolateral corners. Mandibles subtriangular, straight outer margin over 2/3 length, and distally curved inwards; masticatory margin consisting of strong apical tooth, acute and longer than wide; slender subapical tooth, half length of the apical tooth; third triangular tooth half as long as subapical; fourth tooth slightly longer than third, followed by row of tight denticles decreasing in size approaching curvature leading to undifferentiated basal margin, the latter completely smooth or slightly crenulated. Palpal formula 6:4; maxillary palps with the first segment small and cylindrical, second segment conical and wider distally, sixth segment elongated, digitiform, rounded at tip; segments of labial palps relatively similar in size, 1 st and 2nd segments wedge-shaped, 3rd subrectangular, last segment oval, longer than wide, with rounded tip. Clypeus broader than long; anteromedial margin with slight depression, and narrow, barely noticeable; margins lateral to depression relatively straight, those more lateral obliquely straight; posterior margin of clypeus convex, almost reaching base of frontal carinae. Frontal carinae diverging distally. Antennal scapes long, surpassing posterior margin of head by distance similar to length of pedicel, outer margins straight, slightly curved at both base and apex, wider near apical end; pedicel slightly conical with sub-parallel sides, third segment twice as wide as long, fourth-eleventh segments rectangular, much longer than wide, gradually elongating towards apex, last segment twice as long as others, rounded at tip. Eyes relatively large, oval, longer than wide, external margin relatively straight while the internal margin strongly convex, distance from the mandibular insertion approximately 1/2 maximum length of the eye.

Mesosoma. In lateral view, promesonotum strongly convex, forming nearly continuous line; metanotal sulcus broad and relatively deep; dorsopropodeum strongly convex, dome-shaped, at same level or slightly below level of promesonotum, declivitous face straight, inclined between 50–60°. Propodeal spiracle nearly circular, slightly longer than wide, opening laterally, well below half-length of lateropropodeum.

Metasoma. In lateral view, petiole short, flattened dorsal face with sharp apex inclined anteriorly; ventral lobe projecting, with straight anterior face and slightly curved posterior face. First tergum of gaster excavated anteriorly, as in other Tapinoma species.

Body surface and pilosity. Cephalic surface opaque, finely covered with punctures and reticulations forming very small alveoli; abundant pubescence very short. Mandibles relatively smooth and slightly opaque, dorsal surface tenuously foveolate, covered with abundant short suberect hairs, and longer suberect hairs towards middle and basal portion; ventral face with long erect hairs. Dorsal face of clypeus covered with pubescence similar to that of cephalic capsule; anterior clypeal margin with two longer and thicker hairs, one on either side of medial depression, two golden relatively shorter setae than previously described hairs, above the clypeal margin are a pair of thick hairs directed anteriorly.

Mesosoma completely covered with fine reticulations forming alveoli, relatively larger than those of head; surface rough and opaque, with dense whitish appressed hairs, very short and separated, sometimes imperceptible, giving appearance of glabrous surface, only visible in oblique-dorsal position. Legs with relatively fine granular and reticulated sculpture, relatively opaque, completely covered with dense whitish pubescence.

Petiole smooth and shiny, with few short, decumbent hairs near posteroventral margin. Gaster smooth to finely reticulated, relatively shiny, covered with fine dense golden yellowish pubescence; 5–6 erect hairs near posterior margin of fourth tergum, other terga without erect hairs; sternites with two erect hairs per segment.

Coloration. Bicolored, variable in color tone. Head and mesosoma intense dark brown to brown with some regions yellowish brown on the propleura and the dorsum of the promesonotum. Mandibles, maxillary and labial palps, scapes, antennal segments, and legs pale yellow; masticatory margin reddish brown. Gaster brown to pale yellow as legs, but sometimes with contrasting brown bands on posterior margins of each tergum.

Gyne measurements (n= 20): HL: 0.52 (0.43–0.60) mm; HW: 0.51 (0.41–0.60) mm; SL: 0.45 (0.35–0.52) mm; WL: 0.74 (0.59–0.83) mm; CI: 93–104; SI: 81–93.

Gyne diagnosis: Cephalic capsule diverging posteriorly, much wider posterior to the compound eyes than anterior to them. Second segment of maxillary palps triangular, flattened, longer than wide, 3rd and 5th segments much broader and flattened, 3rd and 4th segment almost fused at the ends where they meet, the basal end of the 5th segment inserted into the ventral face of the 4th segment.

Gyne description ( Figs 15–16 ): Head. Capsule cephalic square to rectangular (CI: 93–104), cuneiform; sides of the capsule relatively straight, lateral margin interrupted by the outer margin of the eyes; well-defined posterolateral corners, rounded, continuing to straight posterior cephalic margin, with shallow and wide concavity. Mandibles as in workers. Palpal formula 6:4; first segment of maxillary palps cylindrical and thickened, last segment thickened, digitiform, rounded at tip; segments of labial palps as in workers, but relatively broader and flattened. Dorsal face of clypeus as in workers, except for anterior margin relatively straighter and entire, with a slight mesal concavity. Frontal carinae divergent posteriorly. Scapes long, surpassing posterolateral corners of head by distance similar to length of pedicel; outer and inner margins straight in most of the length but slightly curved distally, wider mid-length; antennal segments as in workers. Compound eyes large, located at middle of length of cephalic capsule, relatively close to clypeal insertion; eyes located laterally, external margin breaking border of the cephalic capsule. Ocelli small, near level of posterior border of head; posterior ocelli near vertex but never breaking vertexal line.

Mesosoma. In profile, pronotum broad, propleura relatively broader than anterior part of pronotum; dorsal surface of mesonotum flattened; metanotum consisting of very thin strip, separated by deep mesonotal groove; dorsopropodeum without distinctive face, bending abruptly on a relatively inclined slope; mesopleuron divided into anepisternum and katepisternum, those divided by marked and relatively deep anapleural sulcus, anepisternum inverted U-shape, katepisternum subquadrate, almost as long as wide; propodeal spiracle circular, with an outer rim like a ring, directed posterad, and located on lateropropodeal face; metapleuron protruding, forming slight depression below propodeal spiracle. In dorsal view, mesoscutum strongly convex anteriorly, with parallel sides, diverging slightly posteriorly; mesonotal groove straight, slightly marked; mesoscutellum wider than long, posterior margin convex; dorsopropodeum restricted to very narrow band, posterior margin rounded bended abruptly on a slope, propodeum with the lateral margins, almost parallel.

Metasoma. Petiole relatively large, longer than wide, petiolar scale very low, restricted to small dorsal projection, inclined, directed anteriorly, with poorly developed lateral carinae; developed ventral lobe, most prominent posteriorly. Gaster as long as the mesosoma, flattened dorsally and slightly convex on ventral face.

Body surface and pilosity. Surface of the head dense and finely punctate; with dense whitish decumbent hairs relatively separate, distance between hairs less than individual length. Dorsal face of mandibles densely covered with short golden hairs, on almost entire surface, except near area behind masticatory margin where they are long and inwardly directed. Maxillary palps covered with very short pilosity; labial palps with short erect and suberect hairs. Clypeus with pubescence as remainder of head, pattern of hairs on anterior margin as described in workers.

Mesosoma opaque, abundantly and finely punctate; lateral regions of mesosoma covered with whitish pubescence, relatively longer than those of head, more abundant on katepisternum and the metapleuron; dorsum of the mesosoma covered with short pubescence, widely spaced, leaving surface partially exposed. Legs covered with short and decumbent hairs.

Metasomal surface finely punctate as mesosoma, but relatively brighter; covered with abundant pubescence; fourth tergite with six long erect hairs near posterior margin, one central pair, and other two towards sides of the tergite.

Color. Head brown to dark brown, mandibles, maxillary and labial palps and antennae pale yellow; mesosoma bicolored, part of mesoscutum, mesoscutellum and legs yellowish brown to pale yellow, dorsum of pronotum and central portion of mesoscutum as spot, mesopleuron, inferior part of propodeum, and metapleuron brown. Petiole yellowish; gaster brown with yellowish brown bands on posterior margin.

Male measurements (n= 17): HL: 0.44 (0.43–0.46) mm; HW: 0.42 (0.41–0.45) mm; SL: 0.39 (0.35–0.43) mm; WL: 0.66 (0.59–0.73) mm; CI: 93–104; SI: 81–93.

Male diagnosis: Third and fourth segment of the maxillary palps widened, oblong in shape, much longer than wide; the basal end of the 5th segment inserted into the ventral face of the 4th segment, like in the female caste.

Male description ( Figs 17–18 ): Head. In dorsal view, head as long as broad, largest width posterior to compound eyes, with lateral margin convex, cephalic capsule converging anteriorly, posterolateral corners rounded, continuous with straight posterior cephalic margin; ventral surface of cephalic capsule relatively flattened. Mandibles long, semifalcate; external margin slightly sinuous, curving inwards distally; masticatory margin straight, with apical tooth relatively large, obliquely directed downwards, subapical denticle overhanging from margin, remainder of margin with very tight denticles, same size, continuing towards the undifferentiated basal margin. Palpal formula 6:4; 1 st segment cylindrical, 2nd segment two times longer than first, cuneiform, 4th segment much wider than 3rd, 5th and 6th segments finger-shaped, the apical with rounded tip. Clypeus broad, relatively high, dorsal face outwardly projected; anteromedial border slightly concave, narrow, with rounded corners continuing toward relatively straight anterior margin, anterolateral margins inclined posteriorly; posterior margin convex but posterior vertex relatively flattened. Frontal carinae straight and semi-parallel at base, curved and diverging distally. Scape long, surpassing posterior cephalic margin by distance slightly less than distance between frontal carinae, scape with lateral margins parallel, outwardly curved from base to medial length, straight for rest of length, pedicel cuneiform, narrower at base, remainder of antennal segments cylindrical, longer than broad, last segment almost twice length of others. Compound eyes very large, oval, two times longer than broad, occupying almost entire lateral portion of head, breaking outline of lateral margins; anterior margin of eye separated from clypeal insertion by distance shorter than minimal width of scape. Ocelli large, located on wide base and relatively higher than dorsal surface of head, slightly below posterior cephalic vertex; anteromedial ocellus relatively smaller than lateral ocelli.

Mesosoma. In profile, propleura broad, flattened, with dorsal border thin, projecting dorsally; mesonotum anteriorly curved, with hump in lateral view, dorsal face relatively straight and high; mesopleuron divided into anepisternum and katepisternum, both delimited by wide and relatively deep anapleural sulcus; anepisternum inverted U-shaped, relatively wider than long, with dorsal margin slightly inclined posteriorly, anterior margin longer than posterior; katepisternum semiquadrate. Dorsopropodeum below level of mesonotum, with long surface, posteropropodeum slightly bulging decline of 90° toward base; propodeal spiracle oval, longer than broad, located on lateropropodeum, opening posteriorly. In dorsal view, anterior line of pronotum visible; mesoscutum slightly triangular with inferior margin truncated, longer than broad; dorsal face of propodeum visible.

Metasoma. In lateral view, petiole with petiolar scale well developed, anterior face relatively high and straight, forming angle with oblique dorsal face that descends posteriorly to declivity; ventral lobe developed, slightly convex. Cupula weakly sclerotized, easily collapsible when specimen pinned; telomeres dorsoventrally broad, obliquely truncated at apex; digitus long and narrow to tip, latter ventrally curved, cuspis located well inside genital capsule, semi-rectangular in lateral/medial view.

Body surface and pilosity. Head surface opaque, softly punctulate; abundant, whitish, appressed hairs. Mandibles smooth, shining, bearing scattered short and long hairs, subdecumbent from base to behind masticatory margin; some hairs long, surpassing external margin. Anterior margin of clypeus with same pattern of hairs as described in worker; more lateral portions with relatively larger curved hairs; dorsal face densely hairy. Scape surface opaque, slightly punctate, covered by very short pilosity, with some hairs relatively longer and suberect in lateral margins; antennal segments with surface granulate, densely covered by short decumbent hairs, with some short suberect hairs.

Mesosoma relatively shining, with some areas notably opaque, puncticulate; surface covered by relatively short dense golden scattered pubescence, more abundant on katepisternum and metapleuron.

Gaster reticulate, with small alveoli; covered by dense golden pubescence, but relatively sparse, leaving uncovered surface; telomeres densely covered by relatively long pilosity, surpassing margin.

Color. Ants completely yellowish brown, except for mandibles, scape and antennal segment, and legs which are whitish, contrasting with the remainder of body.

Larvae: Dolichoderine larvae described by Wheeler and Wheeler (1951), and examined in detail by Jesus et al. (2010).

Distribution: Species of worldwide distribution, especially in humid tropical and subtropical regions in both hemispheres, but also in temperate places ( Wetterer 2009). It is widely distributed within the Neotropical region, except for Chile.

Biology: The ghost ant biology is reviewed in Wetterer (2009), however, I provide here some additional information. Tapinoma melanocephalum exhibits a wide altitudinal distribution. Populations can be found from environments at sea level to almost 2700 m. Some records in Central America and Caribbean islands suggest that this species is generally distributed below 300 m, except for a record from Panama at 1220 m. In contrast, the distribution of populations established in South America is wider, ranging from 0 m to 2700 m; the highest elevations are recorded for the Colombian Andes, especially towards the center of that country (Antioquia, Cundinamarca, Risaralda, and others). In the center and south of South America , most records correspond to altitudes below 600 m (e.g., São Paulo and Rondônia in Brazil) .

Tapinoma melanocephalum is a polygynous species with 1–25 queens per colony ( Bustos & Cherix 1998). In some colonies studied in Santa Marta (Colombia) 2–5 queens were found, typical of the reproductive behavior of other invasive dolichoderine species such as Linepithema humile , Technomyrmex albipes , and other widely distributed Tapinoma species (Guerrero, unpublished data). One of these colonies (collected in October 2015, RJG01263) harbored two queens, 86 workers, 22 larvae and 10 pupae (3 males and 7 workers). Recently, I collected two colonies of T. melanocephalum near the Tayrona National Park (Santa Marta, Colombia: RJG01286 and RJG01289). One of those colonies (RJG01286, neotype series) was nesting in a dead branch on the roadside to Pueblito-Parque Nacional Natural Tayrona, and another one inside a dry branch hanging from the vegetation on the riverbank of a stream. In both cases, the colonies contained dozens of workers, with two queens, many eggs, larvae and worker pupae, but few males.

In addition to multiple queens, colonies can also be composed of workers with relatively modified morphology. A colony collected in Honduras (Cortés, La Lima: MZSP, catalogue # 6878) contained intercaste females. One of intercastes has a pair of vestigial mesonotal wings; one has a forewing on the right side; two have an enlarged mesonotum and wing scars; one has wing primordia on the mesonotum.

Figures

FIGURES 1–12. Tapinoma melanocephalum multifocus images. 1–3) Full face view of the head, profile, and dorsal view of the T. melanocephalum neotype worker; black arrow shows the enlarged segments of the maxillary palps. 4–6) Full face view of the head and profile of T. melanocephalum coronatum lectotype worker. 7–9) Full face view of the head and profile of T. melanocephalum malesianum lectotype worker. 10–12) Labels of T. melanocephalum neotype, T. melanocephalum coronatum and T. melanocephalum malesianum lectotypes, respectively; lectotypes of T. melanocephalum coronatum and T. melanocephalum malesianum were designated after the AntWebteam imagedthose specimens.Photos 1–2 by Tania K.Franco, and photos 3 and 10 by Emira García; photos4–9, and 11–12 by Will Ericson from www.AntWeb.org.

FIGURES13–18. Tapinoma melanocephalumworker, gyne and male habitus.13–14) Full face view of the headand profile of the worker [Colombia: Magdalena, Santa Marta, dry forest plot, (11.2219°N -74.1865°W), 10.x.2015, leg. R. Guerrero, CBUM, Catalogue # CBUMAG:ENT:08463].9–10) Full face view of the head and profile of the gyne [Colombia: Magdalena, Santa Marta, dry forest plot, (11.2219°N -74.1865°W), 10.x.2015, leg. R. Guerrero, CBUM, Catalogue # CBUMAG:ENT:08464].11–12) Full face view of the head and profile of the male [Paraneotype: Colombia:Magdalena, Santa Marta, Calabazo, roadside to Pueblito-PNN Tayrona, nest in dead branch on the roadside, secondary dry forest (11.2825°N, - 74.0239°W), 22.i.2017, leg. R. Guerrero, nest series, RJG01286, MZSP]. All images by Mayron E. Escárraga and Tania K. Franco.

FIGURES19–22. Head of Tapinoma melanocephalum castes showing the shape of the maxillary palps. 19–20) Polymorphism inthe maxillarypalps ofthe workers[Colombia:Magdalena, SantaMarta,dryforest plot,(11.2219°N -74.1865°W), 10.x.2015, leg. R. Guerrero, CBUM, CBUMAG:ENT:08464 and CBUMAG:ENT:08465]. 21–22) Widened segments of the maxillary palps of queen and male [both reproductive castes with same data as workers above, CBUM, CBUMAG:ENT:08466 and CBUMAG:ENT:08467, respectively]. Black arrows indicate fifth maxillary palp inserted in the inner face of fourth maxillary palp. All images by Mayron E. Escárraga.

FIGURES 23–28. Forewings of Tapinoma spp males.23) Tapinoma melanocephalum [Ecuador: Galápagos, Santa Cruz, Bella Vista, 0°41’38.1’’S 90°19’16.8’’W, 180 m, 13.x.2007, H.Herrera#HWH197, ICCDRS0002606 on www.AntWeb.org. 24) Tapinoma luffae male (= T. melanocephalum senior syn.) modified from Kurian (1955). 25) Tapinoma sessile [Mexico: 26 Km N J. María Aguirre, no more data, 20.v.1988. leg. W.P. Mackay, WEMC#10289]. 26) Tapinoma nigerrimum [Spain: Pozuelo, syntype specimen at Naturhistorisches Museum Basel (NHMB, Basel, Switzerland-), CASENT0911578]. 27) Tapinoma sp. [Brazil: Bahia, Ilhéus, Teotônio Vilela, 06.v.1998, leg. S.R.M. Santos, CPDC, no catalogue number]. 28) Tapinoma subtile [Madagascar: Antsiranana, Rés. Analamerana, 16.7 km 123° Anivorano-Nord, -12.80467°S, 49.37383°E, 225m, 4.xii.2004, leg., B.L. Fisher, BLF11379, CASENT0053839]. Black arrow indicates 1m-cu closing to form the discal cell-1; white arrow indicates 1m-cu absence. Note the wide reduction of venation in T. subtile. Photos 23 and 26 by April Nobile and Zach Lieberman, respectively, from www.AntWeb.org. Photos 27–28 by Mayron E. Escárraga.Name of veins and cells are those of Yoshimura & Fisher (2011).