Myopopone castanea

These rare ants, the only species in the genus Myopopone, nest in rotten wood or under bark. Single colonies may be composed of several small nests scattered over a small area. They feed on large, soft-bodied insect larvae and may bring their larvae to food sources rather than attempt to move especially large prey back to their nest.

Identification
The mandibles are long and slender, with numerous (always more than 5) teeth which vary greatly in size and are scattered along the inner margins, and with a sharp, pointed tooth at the tip which is only slightly longer than the next longest tooth. The frontal lobes are large and extend well forward of the insertion point of the scapes, and when viewed from the front they cover the underlying clypeus and often form part of the front margin of the head. The antennae have the last few segments distinctly flattened in cross-section. The petiole has distinct front and upper faces but lacks a rear face, and its attachment to the gaster is broad and approximately the same height as the petiole so that the upper surfaces of petiole and gaster are separated by at most a shallow impression.

Although these ants are superficially similar to some Amblyopone, the presence of expanded and projecting frontal lobes and flattened tips of the antennae will separate these genera.

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: Borneo, Brunei Darussalam, Indonesia, Malaysia, New Guinea, Philippines, Singapore, Solomon Islands, Timor-Leste. Oriental Region: Cambodia, India, Laos, Myanmar, Nicobar Island, Sri Lanka, Thailand, Vietnam. Palaearctic Region: China.

Biology
Wilson (1958) - Both the Karema and Bisianumu collections consisted of workers found under the thick bark of large rotting logs on the floor of rain forests. At Bisianumu workers were clustered with larvae around two large, freshly killed cerambycid larvae on the same log. Since the beetle larvae were well separated from one another, and appeared to be too large for the ants to transport through the preformed galleries under the bark, it is inferred that the ants had transferred their own larvae to feed on the prey after the latter had been attacked and killed. The Myopopone are singularly clumsy and shy ants, and immediately commence searching for cover when exposed to light, abandoning their brood in the process. When handled, however, they are capable of inflicting a painful sting.

Ito (2010) - Workers kept with larvae in the laboratory frequently showed larval hemolymph feeding (hereafter LHF). This behavior is very similar to that of queens of Stigmatomma silvestrii Wheeler as reported by Masuko (1986). Workers pinched the larvae with their mandibles and licked hemolymph from the wounds. Workers most often pinched the dorsal integument of the upper abdomen of larvae. Many large larvae had scars which seem to be made by LHF. During 14 h of observations of an orphan colony with 25 workers, LHF was observed 38 times. Twelve of the 25 workers performed LHF. One worker monopolized more than 50% of LHF (21 times) and the others only showed the behavior one to three times. Among workers, we never observed aggressive behavior. The relationship between LHF and ovarian development could not be examined, because colony condition was unfortunately poor at the end of the observation. During the observation period, no egg-laying occurred.

Among amblyoponine ants, the occurrence of LHF has been reported in Amblyopone spp., Prionopelta kraepelini, Adetomyrma sp., Mystrium camillae and Onychomyrmex (Ito & Billen 1998; Masuko 2003; Saux et al. 2004; F. Ito, unpubl. data, 1989, 2002).

Even though we still do not know whether queens of M. castanea perform LHF, all genera in this subfamily so far observed show LHF. Although LHF has been found in a handful of ant species outside of Amblyoponinae, e.g. a few species of Proceratium (Proceratiinae), a few species of Gnamptogenys (Ectatomminae), Leptanilla japonica and Leptanilla clypeata (Leptanillinae), and Calyptomyrmex sp. (Myrmiciinae) (Masuko 1986, 1989; Ito 2001; Ito & Gobin 2008; F. Ito, unpubl. data, 2001), this aberrant feeding mode is one of the important characteristics of the subfamily Amblyoponinae.

Male
More automontage images can be found here

Nomenclature

 *  castanea. Amblyopone castaneus Smith, F. 1860b: 105, pl. 1, fig. 6 (w.) INDONESIA (Batjan I.). Mayr, 1867a: 90 (q.); Wheeler, G.C. & Wheeler, J. 1964b: 446 (l.). Combination in Myopopone: Roger, 1862c: 292. Senior synonym of rufula: Roger, 1862c: 292; of picea, rossi, similis, smithi, wollastoni: Wilson, 1958a: 144; of bakeri (and its junior synonym proxima), beccarii, bugnioni, maculata, moelleri, striatifrons: Brown, 1960a: 215. See also: Xu & He, 2011: 232.
 * maculata. Myopopone maculata Roger, 1861a: 50 (w.q.) SRI LANKA. Donisthorpe, 1942c: 29 (m.). Subspecies of castanea: Dalla Torre, 1893: 15; Forel, 1900c: 54; Forel, 1907a: 17; Wheeler, W.M. 1919e: 50. Junior synonym of castanea: Bingham, 1903: 33; Brown, 1960a: 215.
 * rufula. Myopopone rufula Roger, 1861a: 52 (w.) INDONESIA (Batjan I.). Junior synonym of castanea: Roger, 1862c: 292; Brown, 1960a: 215.
 * beccarii. Myopopone beccarii Emery, 1887b: 447 (w.) INDONESIA (Ternate I.). Subspecies of castanea: Dalla Torre, 1893: 15; Emery, 1911d: 26. Junior synonym of castanea: Brown, 1960a: 215.
 * moelleri. Myopopone moelleri Bingham, 1903: 34 (q.) INDIA. Donisthorpe, 1942c: 30 (m.). Junior synonym of castanea: Brown, 1960a: 215.
 * bugnioni. Myopopone castanea var. bugnioni Forel, 1913k: 5 (footnote) (q.m.) SRI LANKA. Subspecies of moelleri: Donisthorpe, 1942c: 31. Junior synonym of castanea: Brown, 1960a: 215.
 * bakeri. Myopopone castanea var. bakeri Viehmeyer, 1916b: 283 (w.) PHILIPPINES. Subspecies of moelleri and senior synonym of proxima: Donisthorpe, 1942c: 31. Junior synonym of castanea: Brown, 1960a: 215.
 * proxima. Myopopone castanea var. proxima Stitz, 1925: 110 (w.) PHILIPPINES. Junior synonym of bakeri: Donisthorpe, 1942c: 31. See also: Wilson, 1958a: 145.
 * striatifrons. Myopopone moelleri var. striatifrons Stitz, 1925: 110 (q.) INDONESIA (Lombok I.). Junior synonym of castanea: Brown, 1960a: 215.
 * picea. Myopopone picea Donisthorpe, 1938e: 498 (w.) BORNEO. Junior synonym of castanea: Wilson, 1958a: 144.
 * wollastoni. Myopopone wollastoni Donisthorpe, 1942c: 29 (q.) NEW GUINEA. Junior synonym of castanea: Wilson, 1958a: 144.
 * smithi. Myopopone smithi Donisthorpe, 1947c: 577 (q.) NEW GUINEA. Junior synonym of castanea: Wilson, 1958a: 144.
 * rossi. Myopopone rossi Donisthorpe, 1948b: 297 (w.) NEW GUINEA. Junior synonym of castanea: Wilson, 1958a: 144.
 * similis. Myopopone similis Donisthorpe, 1949b: 488 (q.) NEW GUINEA. Junior synonym of castanea: Wilson, 1958a: 144.

Worker
Length 41/2 lines. Ferruginous; head wider than the thorax, slightly rounded at the sides, and emarginate behind, finely and distinctly punctured above, anteriorly it is longitudinally striated; the anterior margin fuscous; the antennae short and stout; the flagellum clavate; the mandibles with a row of short, stout, acute teeth on their inner margin; the head has a few scattered erect hairs. Thorax: the prothorax subglobose, strongly punctured in front; the mesothorax short and transverse; the metathorax oblong, parallel, and punctured; the apex transversely striated; the legs short, stout, and pubescent. Abdomen: the basal segment strongly punctured, the second and fullowing segments delicately and very sparingly so; the first and second segments deeply constricted at their margins; the apex pointed and pubescent, the pubescence ferruginous.

Xu and He (2011) - L 7.3-8.7, HL 1.57-1.90, HW 1.63-2.00, CI 104-105, SL 0.80-0.93, SI 47-49, ML 1.10-1.20, PW 1.03-1.30, AL 2.20-2.67, ED 0.15-0.18, PH 0.73-0.83, PL 1.03-1.20, LPI 69-73, DPW 0.83-1.03, DPI 81-86 (3 individuals measured).

Head in full face view rectangular, about as long as broad, slightly widen forward. Occipital margin evenly concave. Occipital corners roundly prominent. Lateral sides weakly convex. Clypeus narrow and transverse, anterior margin straight, with a row of about 6 minute denticles. Frontal lobes developed and relatively close together, concealed antennal sockets, protruding forward divergently and surpassed anterior margin of clypeus. Mandibles narrow and linear. Masticatory margin distinct, with 4 teeth, about 1/2 length of inner margin. Inner margin with 5 teeth. Frontal carinae short, extending backward to midline of head. Antennae short and stout, apexes of scapes reached to 1/2 of the distance from antennal sockets to occipital corners. Antennal clubs 6-segmented, incrassate and depressed. Eyes small, with about 15 facets, well behind the midline of the head. Ocelli absent.

In profile view, dorsum of alitrunk relatively straight, lateral sides nearly vertical. Pronotum long, weakly convex. Promesonotal suture and metanotal groove distinctly notched. Mesonotum very short and transverse. Dorsum of propodeum straight, longer than declivity, about as long as pronotum. Declivity roundly convex. Propodeal lobes small, rounded at apex. Propodeal spiracles elliptic and vertical, located at center of the lateral sides. In profile view, petiolar node nearly trapezoid, broadly attached to first gastral tergite. Dorsal face weakly convex, longer than anterior face. Anterior face weakly depressed. Ventral face weakly concave. Subpetiolar process small, nearly rectangular. In dorsal view, petiolar node broader than long, slightly widen backward, anterior margin straight, lateral sides moderately convex. Constriction between the two basal gastral segments distinct. Sting developed and extruding.

Mandibles smooth, with sparse punctures. Clypeus densely transversely striate. Dorsum of head smooth, with sparse punctures, but densely longitudinally striate on anterior portion. Ventral face of head and frontal lobes sparsely longitudinally striate. Lateral sides of alitrunk densely longitudinally striate. Dorsum of alitrunk smooth, with sparse punctures. Posterior 2/3 of propodeal dorsum densely punctate, declivity transversely striate. Dorsal and anterior surfaces of petiole smooth, with sparse punctures, lateral sides longitudinally striate. Dorsum of peduncle transversely striate. Gaster smooth, with sparse punctures.

Head and body with sparse erect to subdecumbent hairs. Clypeus, propodeum, petiole, and gaster with abundant hairs. Gastral apex with dense hairs. Antennal flagella, propodeum, and dorsum of petiole with dense decumbent pubescence. Antennal scapes and hind tibiae with sparse subdecumbent hairs. Outer surfaces of tarsi and middle tibiae with strong spines. Color brownish red. Mandibles, clypeus, frontal lobes, and antennal flagella reddish brown. Eyes grey. Hairs golden yellow.

Queen
Xu and He (2011) - TL 13.7, HL 2.47, HW 2.63, CI 107, SL 1.17, SI 44, ML 1.60, PW 2.07, AL 4.33, ED 0.63, PH 1.27, PL 1.93, LPI 66, DPW 1.70, DPI 88 (1 individual measured). Head similar to the worker, in full face view slightly broader than long, not narrowed forward. Anterior margin of clypeus straight, without denticles. Eyes large, located at midpoints of lateral sides of head. With 3 ocelli. In profile view, alitrunk massive, dorsum nearly straight, mesonotum weakly convex. Propodeal dorsum shorter than declivity, the latter weakly convex. In dorsal view, mesonotum with a pair of oblique longitudinal furrows on anterior portion, and a longitudinal central furrow on posterior portion of scutum. Transverse groove between scutum and scutellum distinct and straight. Posterior margin of scutellum concave. Metanotum crescent, narrow and transverse. Petiole and gaster similar to the worker.

Sculptures similar to the worker, but occipital margin longitudinally striate, lateral sides of promesothorax longitudinal striate and abundantly punctured, propodeal dorsum densely punctuate. Pilosity similar to the worker, but anterior face of petiolar node without hairs, hind tibiae with sparse subdecumbent hairs and abundant decumbent pubescence. Color black. Mandibles, clypeus, apexes of frontal lobes, antennae, and coxae reddish brown. Tibiae, tarsi, and gastral apex brownish red. Ocelli light yellow. Hairs golden yellow.