Monomorium Mayr

Eguchi, K., Viet, B. T. & Yamane, S., 2011, Generic synopsis of the Formicidae of Vietnam (Insecta: Hymenoptera), Part I - Myrmicinae and Pseudomyrmicinae., Zootaxa 2878, pp. 1-61 : 19-20

Monomorium Mayr , 1855

Taxonomy. The genus Monomorium is assigned to the Solenopsis genus group of the tribe Solenopsidini (Bolton 2003). The concept of the genus was revised by Bolton (1987), and was recently widened by Heterick (2003) and Fernández (2007). Workers of Vietnamese species have the following features.

Worker caste monomorphic or polymorphic; head in full-face view subrectangular, with rounded posterior corners; frontal lobe in full-face view narrow, just concealing antennal insertion, not extending posteriorly as a frontal carina, moderately or narrowly separated by posteromedian part of clypeus; antennal scrobe absent; median portion of clypeus expanded anteriad, with a straight anteromedian margin, usually defined laterally by clypeal carinae; median clypeal seta present; mandible narrow; masticatory margin with apical and 2 subapical teeth usually followed by a small or inconspicuous tooth, but sometimes by 1 or 2 distinct teeth (thus the margin 3- to 5-toothed); antenna 11- or 12-segmented, with 3-segmented club; eye medium to small in size (rarely reduced to a single ommatidium); promesonotum in lateral view usually weakly raised; promesonotal suture completely absent dorsally; metanotal suture usually a deeply impressed groove on dorsum; propodeum unarmed, but rarely with posterodorsal angles; propodeal lobe absent or indistinct, but sometimes roundly expanded; petiole pedunculate anteriorly and with distinct node; postpetiole much shorter than petiole, in dorsal view almost as broad as or a little broader than petiolar node; gastral shoulder weak or indistinct, but sometimes well developed; first gastral tergite largely overlapping first gastral sternite.

The worker of Monomorium is similar to those of Anillomyrma (see under Anillomyrma ), Cardiocondyla (see under Cardiocondyla ) and Solenopsis , and to the minor workers of Pheidole and Pheidologeton . However, in the worker of Solenopsis the antennal club is 2-segmented. In the minor of Pheidole the median clypeal seta is absent, the masticatory margin of mandible has 6 or more teeth/denticles, and propodeal spines are usually (but not always) present. In the minor of Pheidologeton the antennal club is 2-segmented, the median clypeal seta is absent, and propodeum is always armed with spines or denticles.

Vietnamese species. Two species have been described from Vietnam: annamense Donisthorpe (type locality: Da Lat) and silvestrii Wheeler (type locality: Yen Bay; other locality: Va n Phu). Ten additional species have been recognized by us from Vietnam: chinense Santschi [= sp. eg-6] (Ba Vi, Cuc Phuong, Tam Dao); floricola (Jerdon) [= sp. eg-7] (Que Phong, Pu Mat); hiten Terayama [= sp. eg-3] (Ba Be, Ba Vi, Cuc Phuong, Tam Dao, Tay Yen Tu, V a n B a n); pharaonis (Linnaeus) [= sp. eg-4] (Ba Be, Ba Vi, Cuc Phuong, Nui Chua, Pu Mat, Quang Tri, Tam Dao); sechellense Emery [= sp. eg-5] (Ba Vi, Binh Chau-Phuoc Buu, Cuc Phuong, Pu Mat); sp. eg-1 [= sp. 9 of SKY: Eguchi et al. 2005] (Ba Vi, Cuc Phuong, Pu Mat, Tam Dao, Tay Yen Tu, Van Ban); sp. eg-2 [= sp. 1 of SKY: Yamane et al., 2003] (Ba Be, Cuc Phuong, Tay Yen Tu); sp. eg-8 (Nam Cat Tien, Phu Quoc, Pu Mat); sp. eg-9 (Nui Chua); sp. eg-10 (Nui Chua, Phu Quoc).

Bionomics. Monomorium species are found in various habitats such as bare lands, grasslands, forest edges and well-developed forests. Their nests are usually found under stones and in soil. Most species forage on the ground, but some, such as M. sechellense , forage both on and under the ground (Eguchi & Bui 2009).