Anillomyrma

Eguchi, K., Bui, T. V. & Alpert, G. D., 2009, Revision of the ant genus Anillomyrma Emery, 1913 (Hymenoptera: Formicidae: Myrmicinae: Solenopsidini)., Myrmecological News 13, pp. 31-36 : 32-33

Anillomyrma Emery, 1913 (Figs. 1 - 15)

Anillomyrma Emery, 1913: 261 [as subgenus of Monomorium ]. Type-species: Monomorium decamerum Emery , 1901: 117; by monotypy. Anillomyrma Emery, 1913: Ettershank (1966): 97 [Raised to genus].

Worker description. By the combination of the characteristics marked by blue asterisks, Anillomyrma is distinguished from the other genera of the Solenopsis genus group (sensu Bolton 2003). Worker monomorphic. Body extensively depigmented, weakly sclerotized (easily shrunk when dry-mounted). Head longer than broad, without preoccipital carina; frontal lobe in full-face view only partially concealing torulus, not extending posteriorly as frontal carina; antennal scrobe absent; median portion of clypeus only weakly expanding anteriad and distinctly raised above the level of lateral portions, *not bicarinate laterally below antennal insertion, *narrowly inserted between frontal lobes; median clypeal seta well developed; 1st paracarinal seta well developed; lateral portions of clypeus not forming a raised rim or shield wall in front of antennal insertions; anterior tentorial pit located at the midpoint of antennal insertion and lateral margin of head in full-face view; mandible elongate-triangular, with 3 or 4 distinctly dark-colored teeth on masticatory margin but without any tooth / denticles on basal margin; a short diastema present between the preapical and 3rd teeth; trulleum small and closed; hypostoma without lateral tooth just mesal to each mandibular base; anterior margin of labrum broadly concave medially; *both maxillary and labial palps consisting of two completely separated segments (see "Remarks "); praementum with a pair of long and simple setae; *antenna 10-segmented, *with 3-segmented club; antennal segments III - VII each much shorter than broad; segment X much longer than segments VIII and IX combined; segments VIII, IX and X with several sensilla tricodea curvata(arrow in Fig. 7) which are long, thick, simple and appressed; segment X with several sensilla ampullacea (arrow in Fig. 8) [i.e., a peg contained in a bottle-shaped chamber (ampulla) which connects apically with a thin duct; the tube opening on the outer surface of the apex of segment X]; *eye completely absent. Mesosoma in dorsal view moderately constricted between promesonotum and propodeum; promesonotum in lateral view low, almost flat or very weakly convex, without conspicuous humerus; promesonotal suture completely absent dorsally; metanotal groove present dorsally as a weak transverse striation; propodeum neither armed posterodorsally nor carinate posterolaterally; propodeal lobe absent; both mesosternum and metasternum without conspicuous ventral tooth; *propodeal spiracle small, situated at or slightly behind midlength of sides of propodeum; metapleural gland relatively large. *Forecoxa robust, *and much longer than middle and hind coxa; meso- and metatibial spur absent. *Petiolar peduncle long, *without any anteroventral process; *petiolar node long, low and dorsally broadly convex in lateral view; postpetiole much shorter than petiole, in dorsal view almost as broad as or slightly broader than petiolar node, *in lateral view broadly attached to top of anterior face of first gastral segment. Gaster elongate; gastral shoulder absent; *sting strongly developed.

Remarks. Ettershank (1966) and Bolton (1987, 2003) mentioned that the labial palp consists of two semifused segments. The separation of the two segments, however, was recognized as a conspicuous notch in silhouette in slide-mounted specimens of both A. decamera (8 specimens from bait # 16xii 08-18) and A. tridens (3 paratypes donated by B. Bolton) (Figs. 5, 14).

In the present article we redefined the genus Anillomyrma based only on the two Asian species, i.e., A. decamera and A. tridens . An "Anillomyrma-like" Monomorium sp. was collected from Toliara, Madagascar, and housed in CASENT (CASENT 0006834: see http://www.antweb.org/). Brian Fisher tentatively determined the specimen as " Anillomyrma mad01", but later he concluded, based on molecular phylogenetic analysis, that it is a member of the genus Monomorium (B. Fisher, pers. comm.). His view is supported by our examination of the worker morphology. CASENT 0006834 is clearly differentiated from A. decamera and A. tridens : antenna 11-segmented; forecoxa not massive; postpetiole narrowly articulated close to center of anterior face of first gastral segment; petiole with very short pedicel and with highly raised node. CASENT 0006834 lacks eyes and has an evenly convex median part of the clypeus without bicarination, which makes CASENT 000- 6834 somewhat different from the majority of Monomorium . The eye, however, is reduced to a single ommatidium in the " Monomorium fossulatum group" and clypeal bicarination is reduced or lost in a few species of Monomorium (see Bolton 1987, 2003, Heterick 2006). Barry Bolton (pers. comm.) informed us that Hamish Robertson, of Iziko Museums of Cape Town, has discovered Anillomyrma species, from Tanzania. His species has only 9-segmented antennae. Unfortunately, we have not yet succeeded in coming in contact with H. Robertson. Lin & Wu (2003) recorded an unnamed species from Taiwan, but, according to Terayama (2009), the Taiwanese material has 11-segmented antennae. The identity has not yet been confirmed by us.

Cover & Deyrup (2007) recently described Dolopomyrmex Cover & Deyrup, 2007 from the US. The genus is morphologically very similar to Anillomyrma but lacks the median clypeal seta. As mentioned by them and also by Eguchi & Bui (2007), the presence or absence of a median clypeal seta has been over-emphasized in the classification of myrmicine ants. However, for the moment, we follow Bolton (2003), in which the two genus groups were recognized within the tribe Solenopsidini based on the condition of the median clypeal seta and the radial cell of forewing. On this basis, the genus Anillomyrma has been placed into the Solenopsis genus group.

Bionomics. K. Eguchi and V.T. Bui collected workers of Anillomyrma decamera in a well-developed dry forest in the southern coastal part of Vietnam, by underground bait-trapping; baits (pork sausage) were buried in sandy soil (for details see Eguchi & Bui in press). On the other hand, J. Caceres, a colleague of D.M. General, collected A. decamera in abandoned agricultural land that had isolated stands of abaca plants ( Musaceae : Musa textilis Née) and jackfruit trees ( Moraceae : Artocarpus heterophyllus Lam .), and was overgrown with tall grasses, upright and creeping bamboos and tree ferns. Ant samples were obtained by sifting a soil core sample taken from a deep sandy loam of volcanic origin. Bolton (1987) collected A. tridens on sandy ground in a lowland rain forest. These facts suggest that the distribution of this species may be affected by soil type. Emery (1901) mentioned that the type material of A. decamera was collected from termite nest(s). Anillomyrma may actively hunt soil invertebrates, including termites, using its well-developed sting to envenomate prey, and it may also scavenge animal matter under the ground. Bolton (1987) tentatively suggested that A. tridens is nomadic. These scattered observations may help us to develop collecting and observing methods for these mysterious ant species.