Myrmica titanica

Almost all specimens have been collected foraging on the ground or on fallen trees in well-developed forest. K. Eguchi (pers. comm.) collected workers emerging from a natural cavity in a tree cut down for timber; unfortunately, he had no tools to cut into the wood to "excavate" the colony. This led us to suppose that M. titanica might be a truly arboreal species living and foraging mainly in the canopy, in which case it might be endangered by excessive logging activities. Specimens were found at altitudes 2000-2200 m.

Identification
Radchenko and Elmes (2010) – A member of the ritae complex of the ritae species group. Except for Myrmica angulata, it differs from all other species of the ritae-complex by the punctated surfaces between the rugae of the petiole and postpetiole. In addition, it is the largest Myrmica species in the World so far discovered, having HW > 1.80 mm, HL > 2.10 mm and AL > 3.30 mm (for details see Radchenko and Elmes 2001a; Radchenko, Elmes and Viet 2006).

Key to Myrmica of Vietnam

Distribution
Northern Vietnam.

Distribution based on Regional Taxon Lists
Oriental Region: Vietnam.

Castes
Known only from the worker caste.

Nomenclature

 *  titanica. Myrmica titanica Radchenko & Elmes, 2001b: 222, figs. 1-7 (w.) VIETNAM. See also: Radchenko & Elmes, 2010: 306.

Worker
Extremely large ants, currently the largest known Myrmica species.

Head longer than wide, with slightly convex sides and occipital margin, occipital corners broadly rounded and upper latero-ventral corners pointed; anterior clypeal margin shallowly but distinctly notched medially; mandibles with 7-8 teeth. Frontal carinae feebly curved, frons wide; antenna! sockets surrounded by a single ruga. Antennal scape long (about the same length as head), gradually and weakly curved at the base.

Alitrunk long and low, with very weakly convex promesonotal dorsum, promesonotal suture visible from above, metanotal groove distinct and deep: metapleural lobes project apically to form sharp teeth. Propodeal spines very long, acute (in the holotype, they converge somewhat from their midlength but in the paratype specimen they are more or less straight, and slightly divergent. Petiole long and narrow; its node slightly longer than peduncle. anterior surface very feebly concave and dorsal surface feebly convex, sloping gradually downwards (seen in profile); postpetiole fig-shaped (from above), slightly longer than high, its anterior surface feebly convex with rounded node dorsum (in profile). Spurs on middle and hind tibiae well developed, distinctly pectinate.

Whole body with very coarse sculpture. Frons between frontal carinae levels with the eyes, with five to seven sinuous rugae. Only frons and genae with sinuous rugae, other part of head dorsum with coarse reticulation. Clypeus with coarse longitudinal rugae; mandibles coarsely striato-rugulose; frontal triangle smooth and shiny.

Alitrunk dorsum, petiole and post petiole very coarsely reticulate; sides of pronotum with reticulation, mesopleurae and sides of propodeum with rugae. Surfaces between rugae of head and alitrunk not punctured, appearing smooth and shiny; petiole and postpetiole finely but distinctly punctured. Gaster smooth and shiny. Abundant long, outstanding hairs on head margins and alitrunk, extremely long hairs on promesonotal dorsum; very abundant, long erect hairs on antennal scapes and tibiae. Colour of alitrunk and head dark reddish-brown, gaster and appendages reddish-brown.

Type Material
Holotype, w, Northern Vietnam, Lao Cai, Sa Pa, Fan Sipan, all. 2020 m, April 1998, leg. B. T. Viet (Kagoshima); para type, 1 w with the same label, probably from the same nest (Elmes)

Etymology
Radchenko and Elmes (2010) - from the word titanic = colossal or gigantic derived from the Titans, the "Older Gods" of Ancient Greece, used here to describe the extraordinary size of this species compared to other Myrmica.