Crematogaster mahery, Blaimer, Bonnie B., 2010

Blaimer, Bonnie B., 2010, Taxonomy and Natural History of the Crematogaster (Decacrema) - group (Hymenoptera: Formicidae) in Madagascar, Zootaxa 2714, pp. 1-39 : 22-23

Crematogaster mahery NEW SPECIES

( Fig. 35 & 41 )

Holotype worker. MADAGASCAR: R.S. Manombo, -23.01580, 47.71900, 30m, 21-22.iv.2006, ex dead twig above ground, littoral rainforest, B.L.Fisher et al. #14050 (CASENT0071537, specimen image on antweb) (deposited in CASC).

Paratypes. 2w, R.S. Manombo, -23.01580, 47.71900, 30m, 21-22.iv.2006, ex dead branch above ground, littoral rainforest (B.L.Fisher et al. #14055: CASENT0193587 and CASENT0193588); 2w, P.N. Andringitra, -22.22350, 47.01176, 780m, 8-9.iii.2010, ex carton nest, riparian rainforest edge (B.B.Blaimer #228: CASENT0193558 and CASENT0193549) (deposited in MCZC, SAMC, MHNG, UCDC).

Material examined. ( BBBC, CASC) MADAGASCAR Toamasina: P.N. Zahamena: -17.75244, 48.85320, 760m; -17.75908, 48.85468, 780m; -17.74300, 48.72936, 860m, -17.73360, 48.72625, 950m (B.L.Fisher et al.); Fianarantsoa: Rés. Andringitra [=P.N. Andringitra]: -22.23333, 47.00000, 825m (B.L.Fisher); P.N. Andringitra: -22.22350, 47.01176, 780m (B.B.Blaimer); R.S. Manombo: -23.01580, 47.71900, 30m (B.L.Fisher et al.); Toliara: P.N. Andohahela: -24.76389, 46.75167, 900m (B.L.Fisher et al.); 13km NW Enakara, Rés. Andohahela [= P.N. Andohahela]: -24.55000, 46.80000, 1250m (B.L.Fisher).

Worker measurements (n=11). HW 1.09–1.21; HL 0.98–1.12; EL 0.24–0.28; SL 0.87–0.97; WL 1.18– 1.32; SPL 0.23–0.41; PTH 0.22–0.26; PTL 0.32–0.38, PTW 0.30–0.39, PPL 0.21–0.28, PPW 0.28–0.37; LHT 0.99–1.07; CI 1.06–1.20; OI 0.23–0.29; SI 0.83–0.92, SPI 0.20–0.33; PTHI 0.64–0.76; PTWI 0.87–1.11; PPI 1.26–1.62; LBI 1.15–1.23.

Worker description. Large to very large (HW 1.09–1.21, WL 1.18–1.32).

Masticatory margin of mandibles with 5 teeth; posterior margin of head straight, laterally subangular; antennal scapes surpassing posterior margin of head easily; midline of eyes situated at or above midline of head in full face view.

Pronotum laterally angular; promesonotal suture broadly impressed, usually complete and continuing laterally to mesopleural spiracle, thereby distinctly constricting mesonotum in relation to pronotum; outline of promesonotum more or less flat in lateral view; antero-medial portion of mesonotum from slightly to prominently raised in respect to pronotum, medially tuberculate; dorsal face of mesonotum medially flat, lateral portion broadly angular; mesonotum postero-laterally angular or tuberculate, and with a distinct posterior face; propodeal spines massive, medium to large (SPI 0.20–0.33), at least longer than width between their bases, evenly tapering, in lateral view from straight to strongly upwards curved, in dorsal view usually moderately to strongly diverging (>20˚); petiole in dorsal view usually hexagonal, not lobed, lacking dorsolateral carinae or tubercule; dorsum of petiole flat; subpetiolar process variable, articulated as round or angular antero-ventral tooth or close to absent.

Head sculpture aciculate; mesosoma with mesopleuron partly shiny, partly rugulose, and metapleuron carinulate to costulate; dorsal face of propodeum costulate, posterior face largely shiny; otherwise mesosoma including legs largely aciculate; dorsal face of petiole mostly shiny, laterally and ventrally coarsely reticulate; postpetiole dorsally feebly rugulose, ventrally reticulate; helcium carinulate; face with 4–6 erect setae; promesonotum with 2 erect humeral setae and sometimes 2 erect setae laterally present on mesonotum; petiole and postpetiole lacking erect pilosity.

Colour medium brown to black, if black then abdominal segment 4–7 sometimes of brown or ochre coloration.

Variation. Populations from P.N. Zahamena and R.S. Manombo possess strongly upwards curved and slightly shorter spines, whereas the P.N. Andringitra and P.N. Andohahela populations have straight, but therefore longer spines.

Comments. This species is closely related to the C. hova -complex and C. sabatra and is hardly separable from the former in the field. It may further be confused with both even under the microscope. Workers of the C. hova -complex reaching the body size of C. mahery usually possess a costulate or areolate head sculpture, not strictly aciculate as in C. mahery . Furthermore, although in size and other characters very similar to C. sabatra , there is only opportunity for confusion of the two at one locality, P.N. Andringitra. Here the two species can be separated by head sculpture: at this locality C. sabatra exhibits a reticulate sculpture pattern that can easily be distinguished from the aciculate head sculpture of C. mahery . The description of C. mahery as a new species is also supported by both mitochondrial and nuclear DNA data.

Distribution and biology. At the moment C. mahery is known only from four localities in Madagascar ( Fig. 55 ). Three localities (P.N. Zahamena, Andringitra and Andohahela) harbour mid-elevation to montane rainforest habitats, the fourth (R.S. Manombo) is home to a rare patch of littoral forest on the east coast. These forests are situated roughly between 250 km and 450 km away from each other along a trajectory of 700 km across the island. It is an intriguing question how this disjunct distribution came about, since it appears that similar potential habitat exists between those localities. A further striking contrast is the species’ distribution in mountainous regions at higher elevations on the one hand, and in the littoral forest at sea level on the other hand. This is the sole Decacrema species recorded from the littoral forest of the R.S. Manombo.

C. mahery co-occurs with the hova -complex at three localities (P.N. Zahamena, Andringitra and Andohahela), and at one locality (P.N. Andringitra) it is also sympatric with C. sabatra and C. malala . Collections mostly comprise workers from beating samples and pitfall and malaise traps, and queens or males of C. mahery have not yet been collected. At R.S. Manombo, Fisher et al. collected workers nesting in dead twigs and branches and in rotten logs. In the Andringitra massif, I was fortunate to find a single colony of these ants nesting in three separate carton nests in a small, solitary tree in an open, riverine habitat. Dissection of the nests yielded only workers and brood, but no queen. This colony housed pseudococcids of an undescribed species of the genus Tylococcus (P.J. Gullan, pers. comm.), feeding inside the carton structure on the main branch around which the nest was constructed.

Etymology. “ Mahery ” means “powerful” in Malagasy, refering to the large body size of workers of this species. The word “ mahery ” is used in this combination as a noun in apposition.

Figures

FIGURES 32 – 37. Malagasy Crematogaster (Decacrema) species; a: full-face view, b: lateral view, c: dorsal view. 32: C. nosibeensis; 33: C. sisa; 34: C. sabatra; 35: C. mahery; 36: C. malala; 37: C. grevei.

FIGURES 38 – 43. Malagasy Crematogaster (Decacrema) species; a: petiole & postpetiole in dorsal view, b: petiole & postpetiole in lateral view. 38: C. nosibeensis; 39: C. sisa, 40: C. sabatra; 41: C. mahery; 42: C. malala; 43: C. grevei.

FIGURES 54 – 57. Distributions of Malagasy Crematogaster (Decacrema). 54: C. grevei; 55: C. mahery; 56: C. malala; 57: C. nosibeensis.