Daceton boltoni

This species seems to be an exclusively canopy-dwelling ant.

Identification
The worker caste of Daceton boltoni shares many important character states with that of its sister species Daceton armigerum, including the heart-shaped head, the large eyes located on a low cuticular prominence (Bolton 2000), the number of apical mandibular teeth, and general habitus. Daceton boltoni differs from D. armigerum by the absence of a specialized row of thick setae on the inner (masticatory) margin of the mandibles; by mandibles that are slightly shorter and more stout, which could indicate differences in prey preferences between the two species (B. Bolton, pers. comm.); by a broad gap, when seen in profile, between the bases of the fully-closed mandibles and the margins of the head capsule; by shallow depressions adjacent to and ventral to the mandibular insertions; by long and simple lateral pronotal spines; by a weakly impressed netanotal groove; and by subdecumbent to decumbent hairs on the tergite of abdominal segment IV. (Azorsa & Sosa-Calvo 2008)

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
Known from Iquitos, Peru, and Manaus, Brazil.

Distribution based on Regional Taxon Lists
Neotropical Region: Peru.

Biology
Specimens of the new species were collected from the canopies of two rainforests in the Amazon watershed, one in Peru and one in Brazil. The Peruvian samples were collected in Iquitos, Loreto. Individual workers were attracted to a bait consisting of a mixture of honey and tuna placed approximately 25 m above the ground on a branch of a Sloanea sp. (Elaeocarpaceae) tree. drop tests conducted at the type locality indicate that D. boltoni individuals exhibit weak and inconsistent aerial gliding behavior relative to those of D. armigerum (S.P. Yanoviak, pers. comm.). Collections were conducted during both day and night. The Brazilian samples were collected by insecticide fogging of a Terra Firma canopy forest within 70 km of Manaus during the dry season (July–August 1979) by T. L. Erwin and co-workers. (Azorsa & Sosa-Calvo 2008)

Castes
Queens and males are unknown.

Nomenclature

 *  boltoni. Daceton boltoni Azorsa & Sosa-Calvo, 2008: 32, figs. 2, 4, 6, 8-16, 20-22 (w.) PERU.

Worker
Holotype. Measurements (mm): EL 0.66, GL 3.29, HL 3.21, HW 3.47, ML 2.34, PL 1.40, PPL 0.55, PSL 1.05, PW 3.13, SL 2.01, TL 13.9, WL 3.07. Indexes: CI 108, MI 73, PI 46, PSI 34, SI 58.

Polymorphic. Head heart-shaped; wider than long. Mandibles elongate and linear with apical fork consisting of two teeth of which the ventral one is the largest. Mandibles finely reticulate-punctate. Inner (masticatory) margin of mandibles with long hairs, lacking any short, thick hairs. Outer margin of mandibles with some decumbent hairs. Mandibles, in full-face view, somewhat short and stout [(MW/ML')*100= 34–44]. Dorsum of clypeus with suberect to subdecumbent hairs. In some intermediate and major castes, dorsum of head with a small but conspicuous ocellus. Ocular carina absent. Ocular crest, in lateral view, with 1–3 erect, simple hairs. Antennal scapes not surpassing the posterior margin of head. Antennal scapes slightly thickening towards the apex, finely reticulate and shiny, and with most of their lengths covered with sparse decumbent to subdecumbent hairs. Base of mandibles, in lateral view, finely reticulate-punctate and ventrally rugose, rest of lateral margin of mandibles smooth and shiny. Sides of head lacking a broad gap between bases of mandibles and margins of head capsule when mandibles fully closed (except in two minors studied, in which case there is a narrow gap). Depressions, adjacent to and ventral to mandibular insertion, shallow (much deeper in Daceton armigerum).

Pronotum with a pair of humeral tubercles that are more carina-like and a pair of lateral, single-tipped (rather than bifurcate) spines. Propleuron, in lateral view, strongly angulate. Posterior portion of promesonotum with a pair of low tubercles. Promesonotum with at least two pairs of standing simple hairs. Metanotal groove weakly impressed. Propodeal spines long and somewhat curved inwards (U-shaped) when seen in fronto-dorsal view. Propodeal spiracles appearing, in dorsal view, as lateral prominences of propodeum; opening of propodeal spiracle longer than wide (oval).

Peduncle of petiole long. Anterior-lateral margins smooth and shiny. Dorsum of petiole anteriorly with a pair of small spines that project latero-posteriorly. Disc of petiole finely reticulate-punctate, lacking a second pair of tubercles or spines. Postpetiole, in dorsal view, hexagonal. Disc of postpetiole finely reticulate-punctate and with appressed hairs. Posterior margin of postpetiole, in lateral view, angulate. Dorsum of first gastral segment mainly with subdecumbent to decumbent hairs in addition to some appressed hairs.

Among the specimens studied, some morphological variation has been documented, including: (i) All castes with sides of head lacking a broad gap between bases of mandibles and margins of head capsule when mandibles are fully closed, with the exception of the two minor workers studied, in which case there is a narrow gap. (ii) Erect hairs on the ocular crest are present in all workers examined. However, the number of hairs varies among specimens. We suspect that these hairs are fragile and can be easily lost, which may account for the variation observed between specimens. This seems also to apply to the standing hairs on the median promesonotum and behind the posterior tubercles of the promesonotum. (iii) Humeral tubercles are strongly reduced, sometimes forming a carina or absent, especially in smaller workers. (iv) The propodeal spines of all of the Peruvian specimens examined converging at the tips (U-shaped, when seen in fronto-dorsal view), whereas in most of the specimens from Brazil the propodeal spines are diverging, more like the state in D. armigerum. (v) Petiolar spines short, almost absent in the smaller castes. The petiolar spines are more developed in the specimens from Brazil.

Type Material
Paratypes. Measurements (mm): EL 0.31–0.79, GL 1.69–3.82, HL 1.08–3.57, HW 1.17–4.13, ML 0.66–2.83, PL 0.67–1.58, PPL 0.24-0.60, PSL 0.28-1.20, PW 0.95-3.60, SL 0.74-2.11, TL 5.68–15.9, WL 1.34–3.55. Indexes: CI 106–116, MI 61–79, PI 41–52, PSI 21–40, SI 51–74, (29 measured).

Holotype worker, Peru: Loreto, Iquitos, ACTS Field Station, Canopy Walkway, 03º15’00’’S 72º55'12’’W, 20–24.iii.2006 (F. Azorsa). [Deposited in .]

Paratypes, 14 workers with same data as holotype; 15 workers, Brazil: Amazonas, Hwy ZF 2, Km 19, ca 60 Km N. Manaus, 02°30’S 60°15’W, 16.viii.1979, Terra Firma (T.L. Erwin et al.). [Deposited in (1), IAvH (1), ICN (1),  (2),  (2),  (6),  (16).]

Etymology
It gives us great pleasure to name this ant in honor of Mr. Barry Bolton for his extensive contributions to the study of ant taxonomy and, especially, to the taxonomy of the tribe Dacetini. His worldwide revision of the tribe Dacetini is a monumental, well-documented work containing well-executed SEM micrographs and a very user-friendly taxonomical key that facilitates identification of the many miniscule, curious species of the tribe.

References based on Global Ant Biodiversity Informatics

 * Azorsa F. and J. Sosa-Calvo. 2008. Description of a remarkable new species of ant in the genus Daceton Perty (Formicidae: Dacetini) from South America. Zootaxa 1749: 27-38
 * Vicente R. E., J. Damborz, and M. Rocha Barreto. 2011. New distribution record of Daceton boltoni Azorsa and Sosa-Calvo, 2008 (Insecta: Hymenoptera) ant in the Brazilian Amazon. Check List 7(6): 878-879.