Linepithema keiteli

An endemic species restricted to mountainous areas of Hispaniola. In places where Linepithema keiteli is found it is one of the most abundant ant species present.

Identification
Wild (2007) - Workers of Linepithema flavescens, another Hispaniolan endemic, are closely similar in structure but have smaller eyes ( < 35 ommatidia), shorter scapes (SI < 85), and are pale yellow in color. Workers of Fuscum-group species on the mainland, Linepithema piliferum, Linepithema tsachila, Linepithema fuscum and Linepithema angulatum, have a punctuate-reticulate sculpture on the head and mesosoma and are less shining. Males of these species have relatively larger eyes (OI > 43) than L. keiteli males.

Discussion: This species exhibits considerable allopatric variation. Worker specimens from the Cordillera Central tend to be darker with larger eyes, slightly longer scapes, and slightly shorter pubescence than Forel’s Haitian types and specimens from Haiti and Sierra Baoruco. Wheeler and Mann’s L. keiteli subfasciatum from Haiti, while somewhat darker than Forel’s keiteli types, falls well within the variation of this species and is synonymized here.

Distribution
Mountains of Hispaniola.

Distribution based on Regional Taxon Lists
Neotropical Region: Dominican Republic, Haiti.

Biology
This species is among the most abundant ants in the mountains of Hispaniola. Collections run from 770 to 1700 meters in elevation. Most records are from montane pine forest down through mesic tropical moist forests, and several collections were made on deforested slopes, forest edges, and roadsides. 21 nesting records are from under stones and four from open soil. Two records are from sifted litter. Colonies are populous and form extensive foraging trails during both day and night. Nests often have several entrances and may extend under series of stones. Of seven nest excavations I conducted in the Sierra Baoruco and the Cordillera Central in November 2002, single dealate queens were found in two of the nests, the rest contained only alate queens or none. This observation suggests that L. keiteli is monogynous and polydomous, although confirmation will require molecular genetic data. One colony was observed tended aphids in a Psidium guayaba tree. L. keiteli workers recruit to dead insects and were observed in the Sierra Baoruco attacking a live dipteran larva.

Alate males and queens have been taken from nests in November, and on one occasion in early November 2002 I observed a partially aborted mating flight at dusk. At 18:00hr, males and workers were observed clustering at several nest entrances of a single colony. By 18:30, males began running about excitedly, climbing grass blades. Workers mostly restrained the males by grabbing the males’ wings, legs, and genitalia with their mandibles, but at least five males escaped and flew straight upward. By 19:30, the activity had subsided and the remaining males were no longer agitated. No queens were observed.

Nomenclature

 *  keiteli. Iridomyrmex keiteli Forel, 1907e: 8 (w.q.) HAITI. Wild, 2007a: 78 (m.). Combination in Linepithema: Shattuck, 1992a: 16. Senior synonym of subfasciatus: Wild, 2007a: 77.
 * subfasciatus. Iridomyrmex keiteli var. subfasciatus Wheeler, W.M. & Mann, 1914: 43 (w.) HAITI. Combination in Linepithema: Shattuck, 1992a: 16. Junior synonym of keiteli: Wild, 2007a: 77.

Wild (2007) - Given the variability of L. keiteli, the recognition of Wheeler and Mann’s Linepithema flavescens as a separate species may render L. keiteli paraphyletic. However, the morphometric variation among populations of L. keiteli is largely continuous, while the variation between L. keiteli and L. flavescens is marked by discrete differences in antennal scape length, eye size, and coloration.

Worker
Wild (2007) - (n = 24) HL 0.59–0.77, HW 0.55–0.75, MFC 0.14–0.20, SL 0.54–0.69, FL 0.45–0.63, LHT 0.47–0.67, PW 0.37–0.48, ES 1.08–1.99, SI 91–103, CI 92–101, CDI 26–30, OI 17–28.

Worker diagnosis: A robust species with a relatively broad head (CI 92–101); antennal scapes in repose surpass posterior margin of head by a distance about equal to length of first funicular segment; mesonotum with sparse medial pubescence, surface smooth and strongly shining; gastric tergites 1–2 each with > 10 erect or suberect setae.

Worker description: Head in full face view slightly longer than broad to about as long as broad (CI 92–101), lateral margins convex, posterior margin slightly to strongly concave. Compound eyes small to moderate size (OI 17–28), comprised of 40–75 ommatidia. Antennal scapes shorter than head length to approximately as long as head length (SI 91–103). In full face view, scapes in repose surpass posterior margin of head by a distance about equal to length of first funicular segment. Frontal carinae moderately spaced (CDI 26–30). Maxillary palps of moderate length, slightly longer than 1⁄2 HL, ultimate segment (segment six) subequal in length to segment 2.

Mesosoma in lateral view with pronotum and mesonotum forming a single continuous convexity, mesonotum strongly convex, without central saddle or indentation, in larger workers meeting dorsal propodeal face at an angle of 90°–110°. Metanotal groove slightly impressed, propodeum depressed well below level of mesonotum. Propodeum in lateral view rounded, not sloping forward, posterior margin convex dorsad of the metapleural bulla. Metapleural bulla protruding.

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

Cephalic dorsum (excluding clypeus) bearing 4–9 erect setae. Pronotum bearing 2–10 (mean = 5.7) erect to suberect setae of varying length. Mesonotum without erect setae, or rarely with a single short suberect seta. Gaster pilose, setae somewhat irregular in length and inclination, shorter setae often difficult to distinguish from pubescence, gastric tergite 1 bearing 10–21 erect setae (mean = 14.8), tergite 2 with 11–26 erect setae (mean = 16.2). Venter of metasoma with scattered erect setae.

Sculpture on head and pronotal dorsum lightly reticulate-punctate and strongly shining. Pubescence dense on dorsum of head, anterior petiolar scale, and gastric tergites 1–4. Pubescence relatively long and subdecumbent. Pubescence on head often fading to sparse laterally. Mesonotal dorsum with moderate to sparse pubescence fading to sparse medially, surface smooth and strongly shining. Lateral face of pronotum, mesopleura and metapleural bulla without pubescence and strongly shining.

Color variable, from head and mesosoma piceous with gaster and appendages medium brown to head and mesosoma light reddish brown with gaster and appendages pale yellow. Lateral clypeal extensions and genae surrounding mandibular insertions lighter in color than remainder of head. Gaster usually lighter than head, tarsi and trochanters lighter than femora and tibiae.

Queen
Wild (2007) - (n = 3) HL 0.93–1.02, HW 0.93–1.02, SL 0.83–0.91, FL 0.89–0.97, LHT 1.01–1.16, EL 0.29–0.32, MML 1.88–2.15, WL 5.98–7.07, CI 100–103, SI 88–90, OI 31–32, WI 32–33, FI 43–47.

Queen description: Relatively large species (MML 1.88–2.15). Head as broad or broader than long in full face view (CI 100–103), posterior margin slightly convex. Eyes moderately small (OI 31–32). Ocelli of moderate size. Antennal scapes of moderate length (SI 88–90), in full face view scapes in repose surpassing posterior margin by a length about that of first funicular segment.

Forewings moderately long relative to mesosomal length (WI 32–33). Forewings with Rs+M somewhat shorter to somewhat longer than M.f2. Legs moderate relative to mesosomal length (FI 43–47).

Dorsum of mesosoma and metasoma with abundant fine suberect to subdecumbent setae, mesoscutum with more than 20 subdecumbent setae. Body, femora, and often antennal scapes dark brown. Tibiae, tarsi, and trochanters lighter in color.

Male
Wild (2007) - (n = 4) HL 0.61–0.70, HW 0.56–0.65, SL 0.21–0.22, FL 0.88–1.06, LHT 0.85–1.10, EL 0.24–0.28, MML 1.31–1.61, WL 3.66–4.68, PH 0.32–0.33, CI 85–98, SI 31–34, OI 37–42, WI 28–29, FI 66–68.

Male diagnosis: Forewing with 2 submarginal cells; eyes relatively small (OI < 43); volsella with distal arm greater than 2/3 length of proximal arm and much longer than height of volsella in lateral view.

Male description: Head slightly longer than broad in full face view (CI 94–98). Eyes relatively small (OI 37–42), occupying about 1/3 lateral surface of head at midlength and separated from posterolateral clypeal margin by a length less than or equal to width of antennal scape. Ocelli of moderate size and in full frontal view set above adjoining posterolateral margins. Antennal scape moderately long (SI 31–34), 85–100% length of 3rd antennal segment. Anterior clypeal margin broadly convex medially. Mandibles large and nearly worker-like, masticatory margin broad, much longer than inner margin, bearing 1–2 apical teeth and 10–14 denticles. Inner margin and exterior lateral margin diverging.

Mesosoma moderately developed, shorter in length than metasoma. Mesoscutum slightly enlarged, not projecting strongly forward or overhanging pronotum. Scutellum large, convex, nearly as tall as mesoscutum and projecting well above level of propodeum. Propodeum in lateral view not overhanging petiole, dorsal face rounding evenly into posterior face, posterior face straight to convex. Forewings long relative to mesosomal length (WI 28–29) and bearing two submarginal cells. Wing color clear to slightly smoky, with darker brown veins and stigma. Legs long relative to mesosoma length (FI 66–68).

Petiolar node bearing a blunt, broadly-rounded scale, node height less than node length. Ventral profile of node convex. Gaster elongate in dorsal view, 2.5–3 times as long as broad. Gonostylus produced as a slender filament. Volsella with ventrodistal process present as a sharp tooth. Cuspis absent. Digitus elongate, distal arm long, at least 2/3 length of proximal arm, and much longer than height of volsella in lateral view. Proximal arm gradually narrowed from 1⁄2 height of volsella at base to filamentous at juncture with distal arm.

Dorsal surfaces of body with scattered erect setae, more than 10 erect setae on mesoscutum. Venter of gaster with scattered setae. Pubescence dense on body and appendages, becoming sparse only on medial propodeal dorsum. Head somewhat shining through pubescence.

Head usually dark brown, darker than body. Body and appendages medium brown. Mandibles, trochanters, tarsi, and terminal antennal segments lighter.

Type Material
Wild (2007) - Lectotype worker, by present designation (, examined), and 3 worker paralectotypes, Port-au-Prince, Haiti, G. Keitel, 6.xii.1901, (,, examined.

Iridomyrmex keiteli var. subfasciatus Wheeler and Mann 1914: 43 (W). Lectotype worker, by present designation (, examined], and 2 worker paralectotypes, Petionville, Haiti, W. M. Mann (, examined). syn. nov.

Additional References

 * Wild, A. L. 2007. Taxonomic revision of the ant genus Linepithema (Hymenoptera: Formicidae). Univ. Calif. Publ. Entomol. 126:vii, 1-151.