Myrmoteras williamsi

Identification
Zettel & Sorger (2011) - Myrmoteras mcarthuri is similar to Myrmoteras williamsi and has been initially mistaken for this species by the first author. However, close examination of material from Leyte yielded the discovery that in fact it represents a distinct new species. Myrmoteras williamsi was described based on sexuals (two gynes and one male) from Los Baños, Laguna, Luzon Island (Wheeler 1919). Moffett (1985) redescribed gynes (types and additional specimens) from Luzon and Negros and workers from Dumaguete, Negros Island. Although he noted important differences between the material from the two islands, he considered them as conspecific, following Creighton (1930).

Myrmoteras williamsi gynes collected at the type locality and deposited in the first author’s collection agree perfectly with the original description of this taxon. Myrmoteras mcarthuri differs in some important characteristics from M. williamsi: In M. mcarthuri the posterior face of the temples, behind a blunt ridge, is granulate, where it is smooth and shiny in M. williamsi. The Mandible Index is larger in M. mcarthuri (145–154) than in M. williamsi (124–130; measurements partly from Moffett 1985). In lateral aspect, the petiolar node is wide in M. mcarthuri, but narrow in M. williamsi. Another very obvious difference is found in the antenna: The funiculus of M. williamsi is stouter than that of M. mcarthuri, especially the basal joints (except antennomere 2) are not much longer than broad in M. williamsi, while their length is almost twice their width in M. mcarthuri. The length of antennomere 3 is approximately 0.7 times the length of antennomere 2 in M. williamsi, but almost 1.0 times in M. mcarthuri. In addition, the length of setae, especially on pronotum, is slightly longer in M. mcarthuri than in M. williamsi.

Although this compares a gyne with a worker, all characters mentioned do not seem to be morph-related, at least there are no differences in the differential diagnoses of worker and gynes of other species (see Moffett 1985).

Myrmoteras mcarthuri differs from Moffett’s (1985) description of “M. williamsi” workers from Negros, as the latter “have a feeble granulate sculpture on the legs, scapes, and mandibles” which is absent in M. mcarthuri. We suspect that this Negros material will turn out being another undescribed species.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Philippines.

Nomenclature

 *  williamsi. Myrmoteras williamsi Wheeler, W.M. 1919e: 146 (q.m.) PHILIPPINES. Creighton, 1930a: 189 (w.). Combination in M. (Myagroteras): Moffett, 1985b: 50.

Determination Clarifications
Zettel & Sorger (2011) - Although Moffett (1985) describes workers from Negros, only sexuals (gynes and males) from Central Luzon belong to M. williamsi  without doubt. At the Discover Life website, Alpert et al. (2010) present another record from Camarines Sur in southern Luzon; however, this record should be reconfirmed, since the first author studied males from the same province which did not fully agree with the M. williamsi-male from the type locality.