Cephalotes specularis Brandão, Feitosa, Powell & Del-Claro, 2014

Brandão, Carlos Roberto F., Feitosa, Rodrigo M., Powell, Scott & Del-Claro, Kleber, 2014, Description of Cephalotes specularis n. sp. (Formicidae: Myrmicinae) — the mirror turtle ant, Zootaxa 3796 (3), pp. 568-578 : 569-578

Cephalotes specularis Brandão, Feitosa, Powell & Del-Claro sp. nov.

Figures 1–7 .

Holotype minor worker. BRAZIL: Minas Gerais: Uberlândia, Clube Caça & Pesca Itororó, -19.004587°, - 48.312506° (hand held GPS with a reported error range of +/- 5 meters), 09.vi.2007, S. Powell col. [ MZSP].

Paratypes. Same data as holotype (4 workers and 2 gynes) [ CPDC]; (7 workers and 2 gynes) [ DZUP]; (4 workers and 2 gynes) [ FMNH]; (200 workers and 14 gynes) [ MZSP]; (4 workers and 2 gynes) [ USNM].

Diagnosis. Polymorphic species of the fiebrigi species group (see clade diagnosis in de Andrade & Baroni Urbani, 1999: 623); eyes situated behind and slightly above the antennal scrobes; vertexal angles without projections; cephalic disc of major worker complete, covered by irregular rugae and erect clavate hairs; minor worker with dorsum of head and mesosoma convex in profile; propodeum with three pairs of lateral denticles; postpetiole with a well-developed ventral process; anterior borders of the first gastral tergite with solid membranaceous extensions; pilosity on the dorsal surface of first gastral tergite scarce to absent; gaster strongly shiny.

Composite description. Minor worker ( Figs 1–2 , 7 ). Holotype (paratypes): HL 1.21 (1.15–1.36); HW 1.21 (1.09–1.39); EL 0.30 (0.27–0.33); PW 0.91 (0.85–1.10); WL 1.24 (1.18–1.39); PTL 0.27 (0.24–0.33); PTW 0.55 (0.52–0.64); PPL 0.24 (0.24–0.30); PPW 0.59 (0.52–0.67); GL 1.33 (1.24–1.58); TL 4.30 (4.12–4.97); CI 100.00 (92.50–102.44); OI 25.00 (22.73–25.64); PI 50.00 (46.78–61.11). Color dark brown to black; frontal lobes pale yellow, with translucid elongate central portions; masticatory margins of mandibles, apices of the antennal scapes and femora, dorsum of the tibiae, body spine tips, and anterior extensions of first gastral tergite light brownish to ferruginous.

Body entirely lightly reticulate-punctate and weakly shiny, except for the gaster which is weakly reticulate and strongly shiny. Mandibles strongly punctate; dorsum of head and mesosoma foveolate, the head foveae tightly accommodate the canaliculated hairs and are more impressed near the vertexal margin and on the pronotal dorsum; external surfaces of femora and tibiae and dorsum of petiole and postpetiole weakly and irregularly foveolate; lateral surfaces of mesosoma with short longitudinal subparallel rugosities; anterior third of first gastral tergite with a few short longitudinal rugosities, originating from the postpetiole insertion.

Pilosity cream-colored and composed by four types of hairs: (1) canaliculated, truncate, thick and appressed, generally originating from each fovea; similar hairs may be present in some parts of body without an associated foveae; (2) clavate and suberect on the mandibles, anterior margin of clypeus, borders of frontal carinae, apex of leg segments, and on the posterior border of gastral segments; (3) long, pointed and subdecumbent on external margins and ventral surface of mandibles, antennal funiculi, surface of abdominal terga 4–7 and on sterna 3–7; (4) minute and appressed, sparsely distributed on the dorsum of the first gastral tergite.

Head ( Fig. 2 a) as broad as long, anterolateral surfaces of frons and frontal lobes depressed. Mandibles with a conspicuous longitudinal lateral angle; anterior margin of clypeus slightly concave and simple, devoid of projections; external margins of frontal carinae (lateral margins of frontal lobes) weakly crenulate; frontal carinae minimally concave in front of the eyes and almost straight over the eyes; vertexal angles truncate, with an obtuse projection near the vertexal margin in full-face view; vertexal margin without projections and narrowly concave medially. Eyes situated behind and slightly above the antennal scrobes.

Mesosoma convex in lateral view ( Fig. 2 c), with a continuous dorsal profile. In dorsal view ( Fig. 2 b), anterior margin of pronotum evenly rounded; pronotum dorsum with two to three lateral pairs of irregular teeth; the first pair comparatively longer and acute and the following ones blunt to truncate. Promesonotal suture visible but shallowly impressed. Mesonotum with a pair of lateral irregular projections. Metanotal suture conspicuous in dorsal view but only weakly impressed. Propodeum with dorsal and declivous faces continuous, and with the lateral margins converging backwards towards the petiolar insertion; in dorsal view, lateral margins of propodeum with two pairs of lateral teeth, the first short and blunt and the second larger and acute; declivous face of propodeum with a single pair of short acute lateral teeth, better seen in lateral view. Mid and hind femora not angulate dorsally; mid and hind basitarsi anteroposteriorly flattened and with subparallel dorsal and ventral faces.

Petiole strongly compressed anteroposteriorly, anterior margin with a discrete, narrow concavity medially, in dorsal view; petiolar dorsum without a transverse carina; lateral petiolar spines well developed and pointed, arising from the anterolateral portion of the petiole and strongly curved backwards; anteroventral process of petiole rounded in profile and expanded anteriorly, but without conspicuous projections. Postpetiole slightly broader than petiole and subtrapezoidal in dorsal view; postpetiolar lateral spines broad and curved backwards; subpostpetiolar process pronounced and anteriorly acute.

Gaster suboval, with a pair of well-developed thick anterolateral lobes, not extending posteriorly in the form of lateral lamellae.

Major worker ( Fig. 3 ). HL 1.61–1.85; HW 1.52–1.73; EL 0.30–0.33; PW 1.33–1.59; WL 1.58–1.82; PTL 0.36–0.42; PTW 0.64–0.73; PPL 0.30–0.39; PPW 0.67–0.79; GL 1.73–2.12; TL 5.58–6.61; CI 92.98–98.18; OI 19.23–20.75; PI 56.87–63.64. Color predominantly black; frontal lobes and margins of cephalic disc yellowish; masticatory margins of mandibles and apices of the antennal scapes dark reddish-brown; lateral expansions of pronotum, apices of femora, dorsum of tibiae and body spines yellowish; first gastral tergite quadrimaculate (two pairs of yellow spots), the first pair close to the anterolateral lobes and the second one laterally placed on the posterior third of the tergite.

Dorsum of cephalic disc ( Fig. 3 a) strongly reticulate-rugose; rest of body superficially reticulate-punctate and weakly shiny. Dorsum of head and mesosoma foveolate, the foveae deeper and contiguous on the dorsum pronotum and mesonotum, slightly sparser and shallower on the dorsal face of propodeum, and only superficial on the ventral surface of head, external surfaces of femora and tibiae and dorsum of petiole and postpetiole; lateral surfaces of mesosoma with thin and short longitudinal subparallel rugosities; anterior third of first gastral tergite with a few short longitudinal rugosities originating near the postpetiole insertion, in a fan-like fashion.

Body with four types of hairs: (1) thick and appressed, generally originating from each fovea, somewhat shorter and thinner on the body parts without foveae; (2) strongly clavate and erect on the mandibles, anterior margin of clypeus, dorsal surface of cephalic disc (where they are particularly dark yellow), apex of tibiae, and on the posterior border of gastral segments; (3) long, pointed and suberect on external margins and ventral surface of mandibles, antennal funiculi, and ventral surface of gaster; (4) minute and appressed, sparsely distributed on the dorsum of the first gastral tergite.

Head slightly longer than broad and dorsally convex. Cephalic disc complete and raised, margins of disc convex posteriorly and strongly concave anteriorly, with lateral margins gently diverging towards mandibles, not completely hiding the eyes; frontal lobes margins and borders of head disc sharp, crenulate and expanded anterolaterally. Vertexal angles truncate and well-projected, without teeth or denticles; vertexal margin without projections and minimally concave medially. Mandibles with a strong longitudinal lateral angle.

Mesosoma almost entirely flat, in lateral view ( Fig. 3 c), except by a discrete anterior convexity formed by the ascending profile of the pronotum. In dorsal view ( Fig. 3 b), anterior margin of pronotum evenly rounded; humeral angles of pronotum considerably expanded and with an anterior pair of acute denticles followed by rounded lamellae. Promesonotal suture feebly impressed. Mesonotum strongly rounded laterally, and without projections. Metanotal suture conspicuous and impressed. Propodeum with well differentiate dorsal and declivous faces, with the latter gently converging posteriorly; in dorsal view, lateral margins of propodeum with a single median pair of obtuse teeth; propodeal spines well-developed, directed upwards, broad basally and acute at apex, in lateral view. Mid and hind femora not angulate dorsally; mid and hind basitarsi anteroposteriorly flattened and with subparallel dorsal and ventral faces

Petiole and postpetiole as in the conspecific worker, but with less developed lateral expansions.

Gaster with the anterolateral lobes protruding anteriorly, but without the membranaceous borders seen in the minor workers.

Gyne ( Fig. 4–5 ). HL 1.70–1.76; HW 1.61–1.67; EL 0.33–0.37; PW 1.45–1.55; WL 2.30–2.36; PTL 0.46–0.55; PTW 0.67–0.73; PPL 0.42–0.48; PPW 0.79–0.82; GL 2.61–2.76; TL 7.61–7.79; CI 93.10–94.64; OI 20.75–22.64; PI 66.09–81.82. Very similar to the conspecific major worker, except by the characteristics expected for myrmicine gynes and a few additional traits (in comparison to workers):

Yellow spots on the gaster occupying a relatively broader area. Foveae sparser over mesossoma and petiole. Pilosity slightly sparser than in the major worker, especially on the dorsum of mesosoma and gaster.

Head ( Fig. 4 a) slightly longer than broad. Vertexal lobes shorter and less pronounced. Posterior portion of cephalic dorsum with a single median ocellus. In dorsal view, pronotum anteroposteriorly narrower than in the major worker and with the lateral projections reduced to small denticles ( Fig. 4 b); scutum large and subtriangular, with the anterior margin strongly rounded; notauli absent; parapsidial lines feebly visible and parallel; transcutal sulcus deeply impressed, but not reaching the lateral margins of mesosoma in dorsal view; scutoscutellar sulcus arched and formed by short and transverse subrectangular foveae; scutellum well-delimited and broad, at the same level as the scutum in lateral view ( Fig. 4 c); dorsal face of propodeum convex and meeting the declivous face in a pair of large short, blunt, and acute teeth.

Wing venation developed, but lacking crossvein 2rs-m, rendering submarginal cell 2 open ( Fig. 5 ). Forewing with a strongly pigmented stigma; anal vein spectral for most of its length, not attaining the cubitus (Cu) vein; media (M) and cubitus (Cu) extending distally beyond stigma as nebulous veins, not reaching the distal border of wing. Marginal cell closed; free R (at apex of marginal cell) long and distant from anterior wing margin; 1rs-m+M abscissa of M arising from Rs+M more than half way between 1m-cu and 2r-rs. Hind wing with R+Rs mostly tubular until the junction with radius (R); M+Cu complete until the junction with radial sector and cubitus (Cu), the latter extending as spectral veins for most of their length and failing to reach the distal border of the wing; around eight submedian hamuli present.

Petiole with lateral projections reduced to a pair of small and blunt denticles. Postpetiole as in the major worker, but with the lateral projections less developed.

Gaster long and subcylindrical with protruding anterolateral lobes.

Male. Unknown (see comments below).

Larva (late instar) ( Fig. 6 ). Length through spiracles: 4.2 mm. Profile pheidoloid ( Fig. 6 c). Segmentation more distinct near the lateral area of the body on the six first gastral segments. No leg or wing vestiges observed under SEM. Prothorax with a ventrolateral boss at each side. No other protuberances present. Anus subventral without lip. Spiracles not visible under SEM.

Integument spinulose, the spinules minute and in short to long subtransverse rows (more common or concentrated in different regions). Body hairs: minute (ca. 10 microns), dispersed and common throughout the body, longer (ca. 40 microns) hairs less common, also dispersed throughout the body. Six pairs of parallel, very approximate, flexuous, very long (200 microns) anchor tipped hairs on AI to AVI along the larva dorsal line; in AI and AII there is a single anchor-tipped hair laterally at each side of the dorsal pair.

Cranium subquadrate, with convex posterior margin ( Fig. 6 a). Head covered by sparse stiff minute hairs with less than 10 micra. Antennae at cranial dorsolateral areas, closer to posterior head margin than to clypeus, as a low circular convexity, only slightly elevated from cranium surface. Clypeus with 7–8 long (ca. 40 microns) stiff hairs, otherwise bare. Rectangular labrum, with almost straight anterior margin, bearing twelve 20 microns hairs concentrated in a row at labrum midlength. Mandible cephalotoid with one apical rounded tooth and no subapical teeth, covered by labrum when closed. Maxillae lobose ( Fig. 6 b), undivided (no discernible cardo and stipes), galea longer and wider than palp, paxilliform (relatively high cylinder) with two sensilla. Palp also paxilliform (low cylinder), with an apical sensillum. Labium hemispheric, with rounded anterior margin. Opening of sericteries not visible. Palp paxilliform, set anteriorly in the labium, with an apical sensilla. Hypopharynx not visible in the studied specimens

Etymology. The specific epithet refers to the reflective property of the minor worker gaster. From Latin “ speculum ” = mirror.

Comments. On morphological grounds, Cephalotes specularis belongs to de Andrade & Baroni-Urbani’s fiebrigi species group. This is further supported by molecular phylogenetic analysis, with C. specularis as a member of a monophyletic clade that contains the fiebrigi and bruchi species groups ( C. specularis is C. sp 1 in Price et al. 2014). Including C. specularis , the combined fiebrigi and bruchi groups comprise 12 species that are present in or limited to the “dry diagonal” (Cerrado, Caatinga, Chaco habitat types) that spans Brazil, Uruguay, Paraguay, and Argentina (de Andrade & Baroni Urbani, 1999; Price at al. 2014). Cephalotes pilosus (Emery) and C. fiebrigi (Forel) were recorded in caatingas in the Brazilian states of Bahia and even in Piauí, but also within the range of the arid diagonal. Members of fiebrigi and bruchi groups share the following characters: minor workers with three to four pairs of denticles on the sides of propodeum; first tergite of gaster with solid and membranaceous anterolateral expansions; and males (known for only four species) with very long gonostyli. However, de Andrade and Baroni-Urbani (1999) mentioned that the number of propodeal spines may be homoplasious among members of other species groups.

Morphologically, C. specularis is undoubtedly closer to C. quadratus (Mayr) than to any other species in the clade. In fact, C. specularis will key to couplet 25 of de Andrade & Baroni-Urbani’s key to minor workers (1999: 738) and may be misidentified as C. quadratus on the basis of the vertexal angles of head without spines, cephalic dorsum covered with erect hairs, and head and mesosoma strongly convex. However, C. specularis can be readily distinguished from C. quadratus by the following features of the minor workers: gaster less sculptured and strongly shiny (rather opaque in C. quadratus ); frontal carinae straight over the eyes (sinuous in C. quadratus ); vertexal angles truncate (rounded in C. quadratus ); first pair of pronotal denticles relatively long and acute (short and obtuse in C. quadratus ); propodeum with barely differentiate dorsal and declivous faces (well differentiate faces in C. quadratus ); and petiolar dorsum without a transversal carina separating the anterior face from the posterior one (transversal carina present in C. quadratus ). In addition, the cephalic disc of C. specularis major workers is strongly reticulate-rugose while major workers have the cephalic disc only superficially foveolate-rugose in C.

quadratus . In fact, the heavily sculptured head disk of the C. specularis major worker is unique among all members of the fiebrigi clade.

Generally, the collection of full colonies of Cephalotes species in the reproductive period of the year leads to the finding of all castes and sexes. The colony from which the types were described was a reproductive colony that had not yet released its sexuals. In addition to this colony, two other colonies were collected from the same population. Although all three of these colonies contained alate gynes, none contained males. De Andrade & Baroni-Urbani (1999) already commented about the scarcity of males in the Cephalotes species of the fiebrigi and bruchi groups; males are known for only four out of the combined total of 12 species. Populations of the species in this group may exhibit split sex ratios (individual colonies specializing in male or female production; Kümmerli and Keller, 2009) as recorded for other Cephalotes species (S. Powell unpubl. data).

There is intraspecific variation is size of both worker castes and queens, as revealed in the ranges of measurements. The yellow pronotal and gasteral spots of major workers and gynes are often absent in the smallest "soldiers" and become more pronounced in the largest ones. Caste intermediates, with blended minor and major worker traits, are moderately common.

As far as we know, C. specularis is restricted to Cerrado areas of Uberlândia, state of Minas Gerais, Brazil. Collections were made from two field stations, the Clube Caça & Pesca Itororó (-19.004587°, -48.312506°) and Estação Ecológica Panga (-19.18235°, -48.39359°). However, the improvement in collection efforts in different localities of the Brazilian Cerrado may reveal new populations of this species.

Cephalotes specularis has been shown to engage in a new form of resource-based social parasitism of the host ant Crematogaster ampla Forel (Myrmicinae: Crematogastrini ), which involves both mimicry of the host ( Fig. 7 ) and eavesdropping on their pheromone trials (Powell et al., unpubl. data). Discovery of additional C. specularis populations will therefore be of great value in examining the nature of this parasitic relationship across the range of both host and parasite.

Cephalotes specularis minor workers assume a peculiar posture, raising their gaster to almost a vertical position when visiting Crematogaster ampla trails (see Fig. 7 b). Minor workers of Cephalotes umbraculatus ( umbraculatus clade of de Andrade & Baroni Urbani, 1999) and C. biguttatus (multipinosus clade, same reference) are able to raise their gasters to an extraordinary degree (up to 112o and 124o respectively) in a defensive posture while secreting clear, volatile fluids from the apex of the gaster that makes them distasteful to predators ( Coyle, 1966). This extreme raise is achieved because of the marked inclination of the declivous face of the propodeum and the low, flat dorsal surface of the petiole, which lacks a truncate anterior face in both species. In C. specularis the petiole has a truncate, perpendicular anterior face in lateral view ( Fig. 2 c) and the gaster is raised up to 70o in relation to the horizontal plane by virtue of the upward flexing of the petiole-postpetiole and postpetiole-gaster joints.

Penick et al. (2012) observed that workers of several myrmicine genera (including Cephalotes ) hang fourthinstar larvae from the walls and ceiling of their nests. This behavior was dependent on the presence of specialized anchor-tipped hairs that occur on the dorsal surface of these larvae, as observed for C. specularis . When larvae received ‘‘haircuts,’’ they were no longer able to adhere to the nest walls. The occurrence of anchor tipped larval hairs in numerous myrmicine genera suggests that larval hanging behavior is common and widespread in this group.

Figures

FIGURE 1. Minor workers of Cephalotes specularis n. sp. walking on a tree in the type-locality. Note the bright blue sky and clouds mirrored on the gaster. Picture taken by S. Powell.

FIGURE 2. Cephalotes specularis n. sp. holotype minor worker in (a) face, (b) dorsal, and (c) profile view.

FIGURE 3. Cephalotes specularis n. sp. paratype major worker (soldier) in (a) face, (b) dorsal, and (c) profile view.

FIGURE 4. Cephalotes specularis n. sp. paratype gyne in (a) face, (b) dorsal, and (c) profile view.

FIGURE 5. Cephalotes specularis n. sp. paratype gyne forewing (top) and hindwing (bottom).

FIGURE 6. Cephalotes specularis n. sp. mature larva (a) head in full face, (b) detail of mouthparts and (c) total larva in profile view. Note the dorsal pairs of anchor-tipped hairs.

FIGURE 7. (a) Crematogaster ampla minor worker in defensive posture on a tree in the type locality of Cephalotes specularis n. sp. (b) Cephalotes. specularis n. sp. mirroring posture of its host C. ampla.