Eutetramorium parvum 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 : 14-15

Eutetramorium parvum Bolton & Fisher sp. n.

(Figs 7-9, Map 125)

WORKER (holotype in parentheses). TL 2.7 (2.7), HL 0.64-0.66 (0.64), HW 0.56-0.59 (0.59), CI 88-92 (92), SL 0.44-0.48 (0.46), SI 78-81 (78), PW 0.38-0.42 (0.40), WL 0.70-0.73 (0.72) (4 measured).

Palp formula 4,2. Cephalic dorsum extremely finely, densely, longitudinally costulate, the costulae diverging and becoming weaker posteriorly; spaces between costulae finely punctulate. Eyes slightly in front of midlength of head in full-face view, EL 0.14-0.15 (EL/HW 0.24-0.25). Sides of head without projecting setae except for a single short seta at the posterior corner. Dorsum of head with a few short, standing setae, and sparse decumbent pubescence. Mesotibia and metatibia without spurs (or spurs so reduced that they cannot be distinguished from apical setae by light microscopy). Metafemur short, MfL 0.52-0.54 (MfL/HW 0.90-0.93). Mesosoma in profile with metanotal groove impressed, the outline of the propodeum just behind the groove rising to a peak, then sloping posteriorly to the spines. Promesonotal dorsum with sparse, short setae. Propodeal dorsum with setae on the crest immediately behind the metanotal groove, but otherwise absent. Pronotal dorsum very finely reticulate-rugulose, the spaces between the rugulae densely punctulate. Petiole in profile with an angulate anteroventral process that is followed by a cuticular crest which extends back to the level of the spiracle; the latter located just anterior to the ascending face of the node. In dorsal view nodes of both petiole and postpetiole broader than long, the postpetiole with length ca 0.20, width ca 0.26. Setae on dorsum of first gastral tergite numerous, short and subdecumbent. First gastral tergite unsculptured except for small pits from which the setae arise. Full adult colour dull yellow to light brownish yellow.

QUEEN (gyne). Presumed alate when virgin, the single specimen known is dealate. TL 3.6, HL 0.75, HW 0.71, CI 95, SL 0.52, SI 73, PW 0.56, WL 1.00, MfL 0.64 (MfL/HW 0.90), EL 0.22 (EL/HW 0.31) (1 measured). Postpetiole dorsal length 0.28, width 0.34. As worker but larger, with conspicuous ocelli and a full complement of flight sclerites. First gastral tergite much broader than in worker (0.87 as opposed to worker ca 0.56). Mesoscutum and scutellum longitudinally costulate.

ERGATOID? A single specimen in the type-series basically resembles a worker, but is decidedly larger, TL 3.0, HL 0.71, HW 0.64, CI 90, SL 0.49, SI 77, PW 0.46, WL 0.82, MfL 0.60 (MfL/HW 0.94), EL 0.16 (EL/HW 0.25). Postpetiole dorsal length 0.24, width 0.28. Otherwise the same as the paratype workers; without flight sclerites but mesonotum more prominent and better defined than in the genuine workers. Maximum width of first gastral tergite 0.64 (ca 0.56 in worker and 0.87 in queen).

As so few specimens are known it is not possible to tell if this individual represents a larger caste of worker, a worker-queen intercaste, or an ergatoid form. Fresh material will be needed, so that this form can be dissected to assess the condition of the ovaries and establish whether spermathecae are present.

MALE: unknown.

Holotype worker (top specimen of 3 on pin), Madagascar: Prov. Toliara, Chaines Anosyennes, Massif Nord, zone summitale, 1900 m., 20.ii.1971, JMB 2048, 2048.8674w, CASENT0195002 (Peyrieras) (CASC).

Paratypes. 4 workers (2 on same pin as holotype), 1 possible ergatoid (see above), 1 dealate queen (gyne); with same data as holotype but the pin bearing the dealate queen with a label, "lavage de sol et litiere. Foret dense humide de montagne" (CASC). [A number of specimens from the same series, in BMNH, are also to be regarded as paratypes.]

Known only from the type-series, parvum is easily distinguished from the two previously known species as it is very small by comparison, is yellow, has a reduced palp formula, is more finely sculptured, lacks mesotibial and metatibial spurs, and despite its small size has eyes that are relatively larger than in its congeners.