Myrmisaraka producta Bolton & Fisher

Bolton, Barry & Fisher, Brian, 2014, The Madagascan endemic myrmicine ants related to Eutetramorium (Hymenoptera: Formicidae): taxonomy of the genera Eutetramorium Emery, Malagidris nom. n., Myrmisaraka gen. n., Royidris gen. n., and Vitsika gen. n .., Zootaxa 3791 (1), pp. 1-99 : 37-39

Myrmisaraka producta Bolton & Fisher sp. n.

(Figs 33-35, Map 133)

WORKER (holotype in parentheses). TL 4.5-5.3 (4.9), HL 0.94-1.09 (1.00), HW 0.73-0.85 (0.77), CI 75-80 (77), SL 0.89-1.10 (0.94), SI 115-129 (122), PW 0.56-0.66 (0.58), WL 1.25-1.42 (1.34), MfL 1.04-1.30 (1.14) (20 measured).

Mandibles finely longitudinally costulate. Pair of setae that straddle midpoint of anterior clypeal margin short and fine, closely approximated, arising within the small concave median notch in the anterior clypeal margin; infrequently only a single seta present. Median portion of clypeus with a series of 4-6 longitudinal rugulae, the median obsolete or obliterated. Eyes large and strongly convex, dome-like, very obviously interrupting the outline of the side in full-face view, EL 0.24-0.30 (EL/HW 0.31-0.35). With head in full-face view the sides shallowly convex, converging posteriorly behind the eyes, the posterior corners broadly rounded and the posterior margin shallowly convex. Occipital carina strongly developed and extends for a short distance onto ventral surface of head, then rapidly peters out just in front of the posteroventral angle. Scapes long (SI 115 or more) with elevated pubescence and a number of short, fine curved setae that are suberect to subdecumbent and inclined toward the scape apex. Antenna with a 4- or 5- segmented club. The 4-segmented club is achieved by the elongation of funiculus segment 8, so that it is 1.55-1.75 x longer than broad. This elongation of funiculus segment 8 brings its length closer to that of segment 9, so that funiculus segment 9 is only 1.00-1.20 x longer than segment 8. In some workers (and in the ergatoid) funiculus segment 7 is also somewhat elongated, so that the club appears weakly 5- segmented. Sides and dorsum of head with numerous fine setae. Head predominantly irregularly longitudinally rugulose, with some cross-meshes, especially posteriorly; spaces between rugulae with feeble ground sculpture of superficial punctulae. Pronotum without an anterior transverse carina; promesonotal dorsum irregularly rugose and the sculpture more strongly expressed than on the head; propodeal dorsum irregularly rugose. In profile, sides of pronotum, metanotum and propodeum reticulate-rugulose, but on mesopleuron the rugulae somewhat stronger and predominantly longitudinal. Propodeal spines long (ca 0.35-0.36), slender and acute, distinctly longer than their basal width in profile; in dorsal view weakly divergent posteriorly. Legs relatively long and slender, MfL> 1.00. All femora and tibiae with outstanding fine setae on all surfaces. Subpetiolar process appears as a small tooth in profile, but in posterior view is seen as a transverse ridge. Peduncle of petiole in profile longer than the node, the latter evenly rounded dorsally. In dorsal view the postpetiole slightly broader than long and broader than the petiole node; postpetiole sides convex and divergent for more than three-quarters of their length, then convergent posteriorly. Sternite of postpetiole distinctly broader posteriorly than anteriorly. Sides and dorsum of petiole and postpetiole very weakly rugulose, but the sculpture almost effaced on the posterior surface of the petiole. First gastral tegite unsculptured. Dorsal surfaces of mesosoma, petiole, postpetiole and first gastral tergite with numerous fine, simple setae; those on the propodeal dorsum confined to the posterior half of its length. Full adult colour uniform yellow to light brown.

QUEEN (gyne). Ergatoid (CASENT0495050, BLF 8146, data below (CASC)). TL 5.2, HL 1.01, HW 0.81, CI 80, SL 0.98, SI 121, PW 0.61, WL 1.34, MfL 1.22 (1 measured). Eyes slightly larger than in worker, EL 0.30 (EL/ HW 0.36); ocelli absent. Anterior clypeal margin medially has only a single seta, but this is off-centre and implies that one seta (the left) has been lost from an original pair. As in some workers funiculus segment 7 is lengthened, so that the club is weakly 5-segmented. Mesonotum enlarged and its margins more stongly defined. Promesonotal suture a broad, shallow impression and the posterior mesonotum defined in profile. Postpetiole and gaster in dorsal view distinctly broader than in worker. Maximum width of postpetiole in dorsal view 0.44-0.52 in worker, 0.65 in ergatoid; of gaster in dorsal view 0.78-0.93 in worker, 1.34 in ergatoid.

A single specimen out of 9 in series BLF 13148 (data below) also appears to represent an ergatoid, but it is not nearly so conspicuous as the one just discussed. Its mesosoma and waist segments are more like the ergatoid form than that of the workers, and the width of its postpetiole (0.54) and gaster (1.10), while much broader than in workers of the same series (0.44-0.50 and 0.85-0.93, respectively), are less than those of ergatoid BLF 8146 (0.65 and 1.34, respectively). Strangely, the head, scape and metafemur of this probable ergatoid are shorter than in the measured workers from the same series, with HL 0.99 (HL 1.02-1.09 in workers), HW 0.80 (HW 0.82-0.85 in workers), SL 0.91, SI 114 (SL 1.04-1.10 and SI 126-129 in workers), MfL 1.12 (MfL 1.26-1.30 in workers). It therefore seems that a range of morphological variation, between obvious worker and obvious ergatoid, is probable.

Holotype worker, Madagascar: Prov. Toamasina, Ile St. Marie, 22.8 km. 44° Ambodifotatra, 20 m., 16.82433, 49.96417, 22.xi.2005, littoral rainforest, BLF 12906, CASENT0344920 (B.L Fisher et al.) (CASC).

Paratypes. 8 workers with same data as holotype but CASENT0344921 to CASENT0344928, inclusive (CASC, BMNH).

The two species known in this genus are obviously closely related and very similar. The characters that separate them involve a number of measureable features, and are discussed under brevis , above. It is interesting to note that even in the few samples currently available, a simple plot of HW against SI indicates that in producta SI increases with increased HW, while in brevis SI decreases with increased HW.

M. producta has mostly been retrieved from rotten logs and leaf litter samples in rainforest, but it also ascends low vegetation while foraging.

Non-paratypic material examined. Madagascar: Prov. Toamasina, Res. Betampona, 34.1 km. Toamasina, BLF 13148 (B.L. Fisher et al.); Prov. Toamasina, RNI Betampona (Fisher et al.); Prov. Toamasina, Ambohidena (Fisher et al.); Prov. Toamasina, Kalalao (Fisher et al.); Prov. Toamasina, R.S. Ambatovaky (B.L. Fisher et al.); Prov. Toamasina, Mont. Anjanaharibe, NNE Ambinanitelo, BLF 8146 (Fisher et al.); putative males: Prov. Toamasina, Res. Nat. Betampona, 34.08 km. Toamasina BLF 19594 (B.L. Fisher); Prov. Toamasina, Ambodiriana BLF 12838 (Fisher et al.).