Solenopsis dysderces

The few specimens known were removed from a small cell about 15 cm below the surface of the soil, while excavating a colony of Araucomyrmex. The depigmentation, reduced eyes and minute size suggest that this species is probably entirely subterranean and may be associated with other ant species through cleptobiosis. (Snelling, 1975).

Identification
A New World thief ant that is a member of the pygmaea species complex.

Pacheco and Mackay (2013) – Worker - The worker is concolorous pale yellow. The head is elongate, sparsely punctate, yet thickened when viewed laterally from the dorsum to the ventral surface. The clypeal carinae are weakly defined. The eye consists of one ommatidium without pigment.

Solenopsis dysderces is similar to Solenopsis leptanilloides (Argentina) as both species have noticeably elongate heads, similar forms of the clypeus and a lack of well-defined clypeal carinae. Close comparison reveals that S. dysderces has a larger head, in length, width and when measured from the dorsal to ventral surface. Solenopsis leptanilloides has a noticeably slender body compared to the more robust S. dysderces. Solenopsis dysderces is only known from the mountains of Chile, while S. leptanilloides is found in Northeastern Argentina. Solenopsis dysderces is also similar to Solenopsis minutissima (from northeastern Argentina). Solenopsis minutissima can be separated as it has a quadrate shaped head, coarse cephalic punctures and a shorter scape.

Snelling (1975) - Worker: Size minute, HL less than 0.5 mm; apical antennomere longer than segments 2-8 combined; eye a single unpigmented facet; frontal punctures fine, sparse.

The minute size, elongate tenth antennomere and reduced eye are suggestive of Solenopsis pygmaea, an Antillean species. I consider it unlikely, however, that the two are the same and have elected to describe the Chilean species as new.

The only other Chilean Solenopsis in which the tenth antennomere exceeds the combined lengths of segments 2-8 is Solenopsis helena. In that species the eye is pigmented and consists of three or four facets. The punctures on the frons are two to three times the diameter of the hairs arising from them and are separated by two to three times their own diameter. The median clypeal lobe is more abruptly produced in S. helena and the node of the postpetiole, in profile, is more strongly elevated.


 * Key to New World Solenopsis Species Complexes

Distribution
Known only from the type locality: Aconcagua, Chile.

Distribution based on Regional Taxon Lists
Neotropical Region: Chile.

Castes
Known only from the worker caste.

Nomenclature

 *  dysderces. Solenopsis dysderces Snelling, R.R. 1975: 2, figs. 1, 2 (w.) CHILE.

Worker
HL 0.40-0.44 (0.44); HW 0.31-0.32 (0.32); SL 0.28-0.31 (0.30); WL 0.44-0.46 (0.45); PW 0.19-0.21 (0.20).

Head. Distinctly longer than broad, CI 70-76 (73), sides approximately parallel, slightly convergent above, occipital margin slightly concave. SI 87-98 (94), apex of scape short of occipital margin by about twice maximum diameter of scape; apical antennomere 1.20-1.30 ( 1.27) times combined lengths of segments 2-8. Eye unpigmented and barely discernible, consisting of a single facet. Clypeus with distinct carinal and paracarinal teeth projecting beyond apical margin. Mandibular formula 1+ 3, basal tooth distinctly displaced basad on upper margin.

Thorax. Slender, PW 0.44-0.46 (0.45) x WL. Thoracic dorsum, in profile, flattened; metanotal groove distinctly and sharply impressed. Propodeum, in profile, without differentiated basal and posterior faces.

Petiole, in profile, robust, anterior peduncle short; anteroventral tooth present, but small. Postpetiole, in profile, with node low, rounded. In dorsal view, nodes of petiole and postpetiole about equally broad.

Vestiture. Head, thorax and petiole with sparse, irregularly spaced erect hairs of variable length. Scape and tibiae with conspicuous short erect to suberect hairs.

Integument. Smooth and shiny. Frons with scattered fine punctures, separated by 4 x or more, a puncture diameter, hardly exceeding in diameter the hairs arising from them. Frontal lobe without conspicuous striae. Clypeus with bicarinate median lobe, otherwise unsculptured. Mandible with sparse fine punctures. Mesopleura without punctures or striae. Side of propodeum with two or three inconspicuous fine striae below.

Color. Pale yellowish, mandibular teeth, clypeal margin and thoracic sutures reddish.

Pacheco and Mackay (2013) - Measurements (n=3). TL 1.26-1.32 (1.28); HL 0.420-0.426 (0.422); HW 0.312; EL 0.024; ED 0.018; SL 0.300-0.306 (0.302); FSL 0.108-0.114 (0.110); CI 73.2-74.3 (73.9); SI 70.4-72.9 (71.6); PL 0.072-0.078 (0.076); PW 0.096; PI 75.0-81.3 (79.2); PPL 0.096-0.102 (0.100); PPW 0.102; PPI 94.1-100 (98.0); WL 0.270-0.288 (0.282); PSL 0.018; PSW 0.024-0.030 (0.028).

Small; concolorous pale yellow; head elongated, longer than wide, finely punctate, punctures sparse, posterior border slightly concave; anterior clypeal margin between lateral teeth concave; lateral clypeal teeth well developed; bumps present at extralateral position; clypeal carinae weakly defined; scape relatively long, minor funicular segments relatively long; eye with one ommatidium, lacking pigment; pronotum finely punctate, punctures sparse; mesopleuron smooth and shiny, lacking sculpturing; propodeal posterior margin rounded; mesopleuron horizontally striated; petiole node rounded, wider than postpetiole viewed laterally, lacking tooth or flange ventrally, but with little bump; postpetiolar node circular viewed dorsally, lacking tooth or flange ventrally.

Moderately hairy, pilosity pale yellow; scape with appressed and suberect hairs; head, mesosoma, petiole, postpetiole and gaster with short (0.030-0.066 mm) suberect hairs of various lengths.

Type Material
Pacheco and Mackay (2013) - Chile, Aconcagua, ca. 3 km N of Zapallar, 28-x-1972, J. H. Hunt # 958 (holotype and 5 paratype workers,, 3 paratypes seen).

Etymology
Gr., dysderkes, hardly seeing, so named because of the reduced, unpigmented eye.

References based on Global Ant Biodiversity Informatics

 * Pacheco J. A., and W. P. Mackay. 2013. The systematics and biology of the New World thief ants of the genus Solenopsis (Hymenoptera: Formicidae). Lewiston, New York: Edwin Mellen Press, 501 pp.
 * Snelling R. R. 1975. Descriptions of new Chilean ant taxa (Hymenoptera: Formicidae). Contributions in Science (Los Angeles) 274: 1-19
 * Snelling R. R., and J. H. Hunt. 1975. The ants of Chile (Hymenoptera: Formicidae) Revista Chilena de Entomología 9: 63-129.