Myrmecorhynchus nitidus

This is the least common species of Myrmecorhyncus, being known from only a handful of specimens from the vicinities of Melbourne and Canberra. Little is known about the biology of this species. Clark (1934) did report the following regarding the type collection: Mr. Greaves informs me that the examples collected by him were in a branch seventy feet from the ground. Two species collected by the late Mr. Thorn were also obtained in trees, but apparently at no great height as Mr. Thorn secured examples whilst searching for Lycaenid larvae.

Identification
Mesosomal dorsum with at most a few scattered erect hairs, legs with appressed pubescence but lacking erect hairs; extensive yellow on clypeus covering at least 1/3 of surface; mandibles completely yellow (except dark teeth); propodeum relatively low and flat and metapleural groove very shallow when compared to Myrmecorhynchus carteri.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  nitidus. Myrmecorhynchus nitidus Clark, 1934b: 44, pl. 3, figs. 13-16 (s.w.q.m.) AUSTRALIA.

Shattuck (2005) - Morphologically this species is similar to Myrmecorhynchus carteri, differing in colour pattern and the shape of the metanotal groove and propodeum. While colour pattern shows considerable variation in Myrmecorhynchus emeryi, this does not seem to be the case here. All known specimens show either the M. carteri or M. nitidus patterns with no intermediate individuals being found. Thus colour suggests that these two taxa are distinct. The shape of the metanotal groove and propodeum also support this conclusion. All known specimens of M. nitidus have the propodeum lower and more angular dorsally compared to M. carteri workers, resulting in the metanotal groove being less distinct and flatter. As with colour, all specimens show one or the other pattern with intermediate forms unknown. Combined, these characters suggest that two separate taxa are involved rather than a single variable species.

Worker
Major Length, 5.5 mm.

Black. Mandibles and clypeus yellow, the latter with a blackish patch on the middle behind; antennae, trochanters, tibiae and tarsi reddish-yellow. Many examples have the apex of mandibles darker.

Smooth and shining, microscopically reticulate throughout.

Hair yellow, very sparse, short and erect. Pubescence absent except on funiculus where it is short and depressed.

Head very slightly longer than broad, broader behind than in front, sides convex, posterior border feebly convex, almost straight. Mandibles almost half as long as head, terminal border furnished with seven large sharp teeth with a small one between them. Clypeus projecting and broadly convex in front. Frontal area small, triangular. Frontal carinae broad and flat, short, one and a half times broader than long, a feeble groove between them, extending to the anterior ocellus. Scapes extending beyond occipital border by almost twice their thickness; first segment of funiculus twice as long as broad, barely as long as the two following together, second to ninth slightly longer than broad, tenth as long as broad, apical twice as long as broad, as long as the two preceding together. Eyes very large and convex, in front of middle of sides. Ocelli small but prominent. Thorax fully twice as long as broad, strongly constricted at the mesonotum. Pronotum one-fifth broader than long, strongly convex in all directions. Mesonotum one and a half times broader than long. A deep and wide constriction between mesonotum and epinotum, the spiracles prominent at the sides on top. Epinotum one-fourth broader than long, strongly convex in all directions. In profile the pronotum and mesonotum forming a single convexity, the suture feebly indicated. Mesonotum much lower, flat on top, rounded into declivity, the latter oblique, almost as long as dorsum. Node twice as broad as long, oval; in profile as long as high, cone-shaped; a faint indication of a tooth on the ventral surface in front. Gaster one and a half times longer than broad. Legs long and slender.

Minor Length, 4.5 mm.

Colour, sculpture and pilosity as in the major.

Head one-fourth longer than broad, sides and occipital border strongly convex, broader behind than in front. Mandibles fully one-third as long as head, furnished with seven large teeth as in the major worker. Clypeus feebly carinate on the basal two-thirds. Frontal carinae slightly more raised at sides. Antennae similar. Eyes and ocelli smaller, the ocelli very small, hardly perceptible. Thorax somewhat similar but epinotum shorter and more convex. Node more slender and sharper above.

Queen
Length, 7.5 mm.

Colour, sculpture and pilosity as in worker major from which it differs as follows: Head almost parallel; occipital border feebly convex, angles rounded. Teeth on mandibles longer and stronger. Clypeus subcarinate on basal half. Eyes and ocelli larger. Pronotum short and convex. Mesonotum large, flat; parapsidal furrows deeply impressed. Scutellum highly polished. Epinotum very short and broad, declivity flat. Node similar. Gaster larger. Legs slender. Wings hyaline. Discoidal cell small.

Male
Length, 6 mm.

Colour, sculpture and pilosity as in the worker.

Head one-sixth longer than broad, much broader behind than in front, sides and occipital border strongly convex. Mandibles fully half as long as head, somewhat sickle-shaped, inner and terminal borders concave, edentate. Clypeus produced, broadly convex in front. Frontal area large. Scapes slender, extending beyond occipital border by one-fifth their length; first segment of funiculus fully twice as long as broad, second to eleventh about one and three-quarter times longer than broad, apical two and a third times longer than broad. Eyes large, convex, placed in front of the middle of sides. Ocelli large and convex. Thorax twice as long as broad. Pronotum fully twice as broad as long, parapsidal furrows, and a short median furrow in front, deeply impressed, truncate and convex in front, tegulae yellow, projecting at sides. Scutellum one and one-half times broader than long, strongly convex above. Metanotum appearing as a narrow deep impression. Epinotum one and two-thirds broader than long. In profile pronotum short and truncate in front, convex, separated from mesonotum by a strong excision. Mesonotum truncate and convex in front, dorsum fiat, slightly raised at sides behind. Scutellum convex, lower behind. Epinotum rounded into declivity. Node almost twice as broad as long, oval, with a feeble longitudinal groove above; in profile one and one-half times higher than long, dome-shaped. Gaster one and one-half times longer than broad. Genitalia exserted, slender. Legs long and slender. Wings hyaline; discoidal cell small.

References based on Global Ant Biodiversity Informatics

 * Clark J. 1934. New Australian ants. Memoirs of the National Museum, Victoria 8: 21-47.