Linepithema cerradense

This species, as its name implies, is associated with cerrado habitat.

Identification
Wild (2007) – Worker A small species (HW 0.44–0.54); head narrow (CI 85–90); antennal scapes in repose exceeding posterior margin of head by less than length of first funicular segment; mesosoma in lateral view compact and somewhat flattened dorsally, propodeum only slightly depressed below level of promesonotum; color testaceous to medium brown, never dark brown or black.

Workers of Linepithema neotropicum have a more convex promesonotum, a more depressed propodeum, a broader head, longer antennal scapes, and are often darker in color. Workers of the smaller species in the humile-group appear superficially similar, but these have dense pubescence on the metapleura. Workers of Linepithema pulex, a similarly small, light-colored ant from the Atlantic forest region have a much more deeply impressed metanotal suture. Males of L. neotropicum are similar in structure to L. cerradense males but tend to be darker in color and larger in size (MML > 0.90).

This species exhibits little variation across its range. Some worker specimens from São Paulo are less pilose than specimens from elsewhere, often lacking pronotal setae, and color appears to vary slightly among sites without much geographic structure to the variation. This species is closely related to, and possibly evolved from, the variable and widespread L. neotropicum (Wild, unpublished molecular data). Perhaps not surprisingly, populations of L. neotropicum from northeastern Brazil share some features in common with L. cerradense, being lighter colored with somewhat shorter pronotal setae, but these ants are otherwise structurally and morphometrically closer to L. neotropicum than to L. cerradense.

Male Forewing with 1 submarginal cell; size small (HL < 0.45, MML < 0.80); petiolar node with dorsal scale taller than long in lateral view; posterior face of propodeum slightly concave, not strongly overhanging petiole; sculpture of head not well developed and surface shining through pubescence; mandibles with apical tooth unusually elongate.

Distribution
Bolivia, Paraguay, eastern Brazil.

Distribution based on Regional Taxon Lists
Neotropical Region: Bolivia, Brazil, Paraguay.

Biology
Wild (2007) - Linepithema cerradense is frequently associated with cerrado habitat. Of seven records where explicit habitat information is recorded, four are from cerrado. Two additional records are from roadsides and one is from rainforest edge. Most collections unaccompanied by habitat data are from regions where cerrado is the predominant habitat type (e.g., Res. Biol. Águas Emendadas, Brazil). L. cerradense have been taken at baits in Goiás, Brazil. Alates have been collected in December flying to a light in Santa Cruz, Bolivia.

I observed two colonies in a Paraguayan cerrado in the Mbaracayú Reserve in November 2002. Nests were in located in open soil and appeared inconspicuous, with an entrance hole scarcely wider than an individual ant surrounded by small piles of excavated earth. Colonies maintain multiple nest entrances or multiple nests, as there were dilute trails of ants across the surface connecting several of the entrances within a 1 meter2 area. Nests are apparently fairly deep, as excavations near the surface failed to yield any chambers or brood. The nesting biology appears similar to that of the closely-related Linepithema neotropicum. Workers were observed carrying pieces of dead arthropods back to their nests, including carcasses of male and worker Pheidole ants.

Nomenclature

 *  cerradense. Linepithema cerradense Wild, 2007a: 37, figs. 27, 28, 66, 104 (w.q.m.) PARAGUAY.

Worker
Holotype: HL 0.57, HW 0.52, MFC 0.14, SL 0.50, FL 0.42, LHT 0.46, PW 0.33, ES 1.45, SI 96, CI 90, CDI 27, OI 25. Additional workers (n = 17) HL 0.50–0.59, HW 0.44–0.54, MFC 0.11–0.14, SL 0.44–0.53, FL 0.38–0.45, LHT 0.39–0.49, PW 0.29–0.36, ES 1.14–1.57, SI 96–104, CI 85–90, CDI 24–28, OI 19–28.

Head in full face view narrow (CI 85–90), lateral margins convex, posterior margin straight. Compound eyes of moderate size (OI < 19–28), comprised of 50–65 ommatidia. Antennal scapes relatively short (SI 96–104), shorter than head length. In full face view, scapes in repose exceeding posterior margin of head by a distance less than length of first funicular segment. Frontal carinae relatively narrowly spaced (CDI 24–28). Maxillary palps of moderate length, approximately ½ HL, ultimate segment (segment 6) as long or longer than segment 2.

Mesosoma in lateral view compact and somewhat dorsally flattened relative to most other Linepithema. Pronotum and mesonotum forming a single continuous convexity, dorsal promesonotal profile slightly convex, mesonotal dorsum without central saddle or indentation. Metanotal groove slightly impressed to not at all impressed, propodeum only slightly depressed below level of promesonotum. Dorsal propodeal face relatively straight and sloping slightly downward, slope often subparallel to slope of dorsal face of promesonotum.

Petiolar scale relatively sharp and inclined anteriorly, in lateral view falling short of propodeal spiracle.

Cephalic dorsum (excluding clypeus) lacking erect setae. Pronotum with 0–2 erect setae (mean = 1.2). Mesonotum without erect setae. Erect setae on gastric tergites 1–4 ( = abdominal tergites 3–6) sparse, tergite 1 bearing 0–2 erect setae (mean = 0.3), tergite 2 bearing 0–4 erect setae (mean = 1.8), tergite 3 bearing 0–5 erect setae (mean = 2.9). Venter of metasoma with scattered erect setae.

Sculpture on head and mesosomal dorsum shagreened and dull to slightly shining. Pubescence dense on head, mesosomal dorsum, anterior petiolar scale, and gastric tergites 1–4. Mesopleura and metapleural bulla without pubescence and strongly shining.

Color testaceous to medium brown, gaster often darker than mesosoma.

Queen
(n = 2) HL 0.72–0.78, HW 0.62–0.66, SL 0.58–0.65, FL 0.58–0.66, LHT 0.62–0.70, EL 0.22–0.27, MML 1.27–1.66, WL 4.80, CI 85–86, SI 94–99, OI 31–34, WI 29, FI 40–46.

Relatively small species (MML < 1.7). Head narrow in full face view (CI 85–86), posterior margin slightly concave. Eyes moderately small (OI 31–34). Ocelli small. Antennal scapes of moderate length (SI 94–99), in full face view scapes in repose surpassing posterior margin by a length less than length of first funicular segment.

Forewings moderately short relative to mesosomal length (WI 29). Forewings with Rs+M more than twice as long as M.f2. Legs moderate to short relative to mesosomal length (FI 40–46).

Dorsum of mesosoma and metasoma with standing setae sparse, mesoscutum bearing 1–4. Body color testaceous to medium brown. Antennal scapes, legs, and mandibles lighter.

Male
(n = 1) HL 0.41, HW 0.38, SL 0.11, FL 0.40, LHT 0.36, EL 0.20, MML 0.74, WL n/a, PH 0.15, CI 93, SI 26, OI 47, WI n/a, FI 54.

Head longer than broad in full face view (CI 93). Eyes of moderate size (OI 47), occupying much of anterolateral surface of head and separated from posterolateral clypeal margin by a length less than width of antennal scape. Ocelli of moderate size and in full frontal view set above adjoining posterolateral margins. Antennal scape short (SI 26), about 3/4 length of 3rd antennal segment. Anterior clypeal margin convex medially. Mandibles moderately sized and somewhat elongate, masticatory margin broad, longer than inner margin, apical tooth enlarged as a sharp spine and followed by a series of 8–18 denticles. Inner margin and exterior lateral margin parallel to slightly diverging.

Mesosoma moderately developed and subequal in length to metasoma. Mesoscutum not greatly enlarged, projecting slightly forward over pronotum. Propodeum in lateral view not strongly overhanging petiole, posterior face slightly concave. Forewings bearing one submarginal cell. Wings transparent, with pale whitish yellow wing veins and stigma. Legs of moderate length relative to mesosoma (FI 54).

Petiolar node bearing an erect scale, node height taller than node length. Venter of node bearing a convex downward-pointing process. Gaster ovoid in dorsal view, about 2 times as long as broad. Gonostylus produced as a pointed, triangular pilose lobe. Volsella with cuspis present, digitus short and downturned distally.

Dorsal surfaces of body with erect setae sparse, mesoscutum lacking standing setae. Venter of gaster with scattered setae. Pubescence dense on body and appendages, becoming sparse only on medial propodeal dorsum. Sculpture on head and mesoscutum not well developed, surface shining through pubescence.

Head, mesosoma and metasoma testaceous. Mandibles, antennae, and legs pale whitish-yellow to light brown, lighter than body.