Mycetophylax auritus

Preferentially nests in rotten wood in an advanced state of decay.

Identification
Kempf (1964) - Mycetophylax auritus is a highly distinctive species and its closest relative is Mycetophylax strigatus, a smaller sympatric form, from which it is however easily separated by the characters given in the key.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Biology
Kempf (1964): Moeller (1893) found this species to be rather common in the environs of Blumenau, where he performed his pioneering studies on the fungus culture of Attine ants. Excluding strays, he detected about 50 colonies of auritus and Mycetophylax strigatus, the exact number for each species is not given. Nests are preferably established in rotten wood in advanced state of decay. Cavities are generally small, usually not measuring more than 8 cc in volume. One nest, under the bark of a decaying log, was flat, measuring 15 by 15 cm. Like most small Attini, C. auritus workers were feigning death upon being disturbed, but recovered more speedily from the cataleptic state than Apterostigma workers. The fungus garden consisted of a regular sponge-like mass similar to that of Apterostigma pilosum and Apterostigma moelleri, built upon the floor of the nest. The substrate consisted mainly of insect feces. In artificial nests the ants accepted eagerly saw-dust and manioc flour as substrate. Although the specific identity of the fungus is not known, it seems to be a basidiomycete. The gongylidia of the fungus cultivated by auritus are irregular in shape and thickness (cf. Moeller, pl. 7, fig. 25), different from those obtained in the culture of strigatus nests. In captivity both species accepted and ate each others' fungus, rejecting however that of Apterostigma and Acromyrmex.

The colony discovered by Spitz in the vicinity of Alto da Serra, São Paulo State, consisted of approximately 30 workers and 1 dealate queen. The nest was in a decaying log in the forest. The substrate consisted of small vegetable debris, which gave the alcohol, in which it was preserved, a greenish color. The colony encountered by Lenko at Boracéia was also in a decaying log, facing another log, and numbered 32 workers and 1 female.

Luederwaldt's (1926) observations agree essentially with the preceding data. He found a nest of auritus, containing approximately 60 workers between epiphytic roots, in an artificially enlarged cavity. The fungus garden was subglobular, having half the size of a chicken's egg. Upon opening the nest, the ants fell into the well-known cataleptic state.

Nomenclature

 *  auritus. Cyphomyrmex auritus Mayr, 1887: 559 (w.q.m.) BRAZIL.
 * Combination in Mycetophylax: Sosa-Calvo et al., 2017: 9.
 * See also: Kempf, 1964d: 9.

Worker
Kempf (1964): Total length 4.1-4.8 mm; head length 1.01-1.25 mm; head width 0.85-0.99 mm; thorax length 1.28-1.47 mm; hind femur length 1.20-1.47 mm. Yellowish brown to dark reddish brown. Integument densely granular, opaque, including antennal scrobe.

Head as shown in Fig. 1. Mandibles with 8-9 teeth. Clypeus: anterior border mesially excised, middle portion obliquely raised towards front, with two prominent teeth next to origin of frontal lobes. Two pairs of longitudinal carinae on dorsum of head, one in front, following the impressed frontal area, the other more widely spaced on vertex. Supraocular tooth conical and prominent, with a subcarinate ridge arising from its base and extending obliquely backwards to the inferior occipital angle on sides of head. Inferior or outer border of antennal scrobe only vestigially carinate between eyes and occipital lobes. The latter auriculate or horn-like, each considerably longer than its maximum width. Lower border of sides of head carinate. Antennal scape in repose not projecting beyond tip of occipital lobe. All funicular segments distinctly longer than broad.

Thorax as shown in Fig. 13. Pronotum: anterior and lateral border of dorsal face marginate to carinate; a single low conical median tubercle on disc; lateral tubercles low, tooth-like; antero-inferior corner with a small, subacute tooth. Mesonotum: 2 pairs of long conical teeth, the anterior pair longest. A broad and deep impression between the posterior mesonotal tooth and the anterior end of the paired longitudinal carinae of basal face of epinotum, which terminate posteriorly in a small tooth. Legs slender and long; femora lacking carinate ventral edges; hind femora not conspicuously dilated nor ventrally angulate on basal third.

Pedicel as shown in Figs. 13 and 25. Petiole, in dorsal view, with a quadrate node, anterior corners angulate, dorsum with a pair of short, tooth-like ridges. Postpetiole usually not broader than long, its sides subparallel; in profile, perpendicularly raised in front below the prominent, paired, anterior tubercles, connected with the paired posterior tubercles by subparallel longitudinal blunt ridges; space between ridges excavate, more deeply so on posterior half. First tergum of gaster with a pair of median and another pair of lateral sharp longitudinal carinae, the median pair often tuberculate near its anterior end.

Hairs appressed, scarce, minute, fine, not scalelike, slightly more conspicuous along ridges, on spines and on tubercles; still more prominent on scapes and legs.

Queen
Kempf (1964): Total length 5.4 mm; head length 1.20 mm; head width across supraocular spine 0.99 mm; thorax length 1.65 mm; hind femur length 1.60 mm. Very much like the worker, with the differences of the caste. Head exactly as in worker, with the same prominent occipital lobes. Anterior half of middle portion of clypeus perpendicular to posterior half, wedged in between frontal carinae, both faces forming at their junction a marked emarginate edge between the lateral clypeal teeth. Lateral ocelli situated on the outer face of the paired ridges of vertex. Pronotum with a single median tubercle, and a lateral tooth on each side, the latter connected with the anterior border by a low but marked carina, separating the dorsum from the sides of pronotum; antero-inferior tooth acute and prominent. Scutum with a broad and deeply impressed Y-like furrow, the area between the arms of the Y raised, laterally marginate, mesially excavate; lateral areas forming a blunt and raised tuberosity mesad along stem of Y-shaped furrow, being excavate laterad, with a deeply impressed pit near border forming a prominent, upturned ridge. Scutellum antero-mesially impressed, paraptera with a prominent tubercle; postero-mesial portion of scutellum bidentate, with a low; blunt tubercle preceding each tooth. Epinotal spines subtriangular, blunt at apex, prominent. Legs as in worker, but femora ventrally faintly marginate yet not incrassate at basal third, not forming an angle on flexor face. Petiole as in worker, but postpetiole is decidedly transverse, i. e. the sides are conspicuously diverging caudad, the anterior tubercles are slightly lower and the posterior tubercles are more widely separate. Gaster with the two pairs of longitudinal sharp carinae as in worker.

According to Mayr's description, the female lacks a median pronotal tubercle. The two queens observed by myself have a rather well-developed median tubercle, as stated in the description. Perhaps this is a variable feature.

Type Material
Kempf (1964) - In the Mayr collection at the "Naturhistorisches Museum", Vienna, Austria; not seen. A single worker, from Santa Catarina State, formerly belonging to the H. v. Jhering collection (now DZSP), is probably a syntype of Mayr's original series, as suggested by the peculiar type of mounting.