Daceton

A striking and, within its range, commonly encountered member of the arboreal ant fauna.

Identification
Key to the two Daceton species.

Pronotal humeral spines bifurcate, the anterior tip larger than the posterior one. First gastral tergite without standing hairs (sometimes with very short, appressed hairs). Mesonotum and metanotum divided by a strongly impressed metanotal groove. Inner (masticatory) margin of mandibles with a row of short think setae. . . . . Daceton armigerum

Pronotal humeral spines long and simple. First gastral tergite with suberect to subdecumbent hairs. Mesonotum and metanotum divided by a weakly impressed metanotal groove. Inner (masticatory) margin of mandibles lacking a row of short thick setae. . . . . Daceton boltoni



Distribution
Neotropical. South American rainforests.

Biology
Azorsa & Sosa-Calvo (2008) - The monotypic ant genus Daceton Perty (Myrmicinae: Dacetini), and its hitherto known sole species Daceton armigerum, is restricted to South American rainforests (Kempf 1972, Fernández & Sendoya 2004, Bolton et. al. 2007). In this region, Daceton and the larger species of the genus Cephalotes are arguably the most morphologically striking arboreal ants. Daceton usually nests in cavities in the branches and trunks of trees previously bored by beetles and other insects. Blum and Portocarrero (1966) and Moffet and Tobin (1991) state that colonies of D. armigerum contain up to 2500 individuals, whereas Wilson (1962) and Hölldobler & Wilson (1990) estimate that colonies contain between 5000 to 10000 workers. Daceton armigerum has a complex continuously polymorphic caste system, in which smaller workers nurse the brood and larger workers hunt, dismember prey items, and defend the nest (Wilson 1962; Oster & Wilson 1978; Hölldobler & Wilson 1990). Wilson (1962) reports that workers of this highly predaceous myrmicine ant hunt individually for a variety of live insects, including flies, grasshoppers, larvae and adults of moths and beetles, and fulgorids. In addition, some workers have been observed tending coccids (Bodkin in Crawley 1916; Brown & Wilson 1960; Wilson 1962). (Refer to Wilson [1962] for further information on the behavior of D. armigerum.) Recently, Yanoviak et al. (2005) found that individuals of D. armigerum show controlled aerial descent behavior. The genus has been considered primitive with respect to other members of the Dacetini (Brown and Wilson 1959; Bolton 1998, 1999, 2000), but a phylogenetic analysis of the tribe is necessary to fully understand the relationships of its constituent species and genera. Current molecular phylogenetic evidence suggests that Dacetini may not be monophyletic (Brady et al. 2006).

Nomenclature

 *  DACETON [Myrmicinae: Dacetini]
 * Daceton Perty, 1833: 136. Type-species: Formica armigera, by monotypy.
 * Daceton senior synonym of Dacetum: Brown, 1973b: 179.
 * DACETUM [junior synonym of Daceton]
 * Dacetum Agassiz, 1846: 332, unjustified emendation of Daceton.
 * Dacetum junior synonym of Daceton: Brown, 1973b: 179.

Worker
Bolton (2000) - Mandibles linear and elongate, with kinetic mode of action, each with an apical fork of 2 teeth that overlap at full closure; lower tooth of apical pair the largest; preapical dentition absent. Base of mandible highly polished dorsally and with a longitudinal deep cleft that extends distally from the vicinity of the mandalus. Mandibles at full gape open to 1 700 or more. Basal process of mandible a broadly rounded shallow lobe; at full mandibular closure process is dorsal to labrum and fits into a mediodorsal impression on labrum. Palp formula 5, 3. Labrum roughly T-shaped, short and not capable of reflexing to conceal the labio-maxillary complex, which is permanently exposed. Each lateral labral arm locks into a deep emargination near the inner mandibular base at closure. A single long trigger hair arises from each transverse arm of the T-shaped labrum. Side of head with a broad gap between base of mandible and margin of head capsule when mandibles fully closed. Frontal lobes absent; antennal socket surrounded only by an enlarged torulus, the dorsal part of the torulus hypertrophied above the condylar bulb. Eye large, set upon on a broad low cuticular prominence, not sessile, not located ventrolaterally on side of head. Occipital foramen located very high on occiput. Antenna with 11 segments, without a distinctly differentiated club. Scape, when laid back in its normal resting position, passes below the eye; apical portion of extended scape curved anteriorly when seen in full-face view; scape not abruptly downcurved near base. Scrobe absent. Pronotal humeri spinose; mesonotum with a pair of sharp tubercles. Propodeal spiracle high on side and far forward, at about the midlength of the sclerite. Orifice of propodeal spiracle vertically oval, not round. Metapleural gland bulla with its apex widely separated from propodeal spiracle; orifice of metapleural gland posterior, visible. Waist segments without spongiform tissue and without lateral laminar cuticular processes; petiole node bidentate; postpetiole not dorsoventrally flattened ; postpetiolar spiracle lateral. Limbus absent from first gastral tergite; suture between first gastral tergite and sternite evenly rounded laterobasally; basigastral costulae absent.