Dolichoderus gibbifer

A mountain forest inhabitant of Java.

Identification
Dill (2002) - D. gibbifer is well characterized by the shape of the mesonotum and the propodeum in collection with the sculpturing of head and alitrunk. D. gibbifer, and particularly its East-Javanese populations (previously separated as “gibbosior”) is morphologically close to Dolichoderus erectilobus from Northern Thailand and Indochina. The two species are similar in regard to the micro-imbricate sculpturing of the head that macroscopically appears as evenly and very densely punctate. Also, the profile of the alitrunk is very similar. However, gibbifer differs from erectilobus in the presence of an additional coarser rugose surface sculpturing of the alitrunk (in erectilobus entire alitrunk only evenly and finely punctate), the less distinctly expanded corners of the posterior margin of the propodeum (which form distinct cones in erectilobus), the shining declivity of the propodeum (matt in erectilobus), and the pattern of pubescence on the gaster tergites (merging in a median line in gibbifer, not so in erectilobus).

Apart from some paralectotypes without any exact locality (leg. Gribodo), all examined material comes either from a ± limited region in West Java (Cibodas/Gunung Gede, Gunung Salak) or from East Java (Nongkadjadjar). The East-Javanese material differs from the West-Javanese in several characters and had been originally described by Forel as separate var. gibbosior. The main differences of the latter to the typical West-Javanese gibbifer lie in the weaker developed rugose sculpturing of the mesopleuron, the generally scarcer pubescence, the more distinctly laterally expanded corners of the propodeum and the somewhat higher rising rounded-coniform mesonotum hump (although the hump does not in profile ascend steeper than the dorsal face of the pronotum, as claimed by Forel).

There are clinal transitions of several of these characters, for instance regarding the height of the mesonotum hump (intermediate position of the Gunung Salak series) and the shape of the propodeum (paralectotypes leg. Gribodo).

Distribution
Dill (2002) - Mountain forests of higher altitudes in West and East Java. The species presumably also occurs in Central Java, but no material from this region was available for examination.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia.

Biology
Dill (2002) - According to Franz (1975a: 413, 1975b: 265), D. gibbifer is distributed over the entire island of Java in altitudes above 900 m.

In West Java, D. gibbifer is associated with Hippeococcus wegneri. Jacobson (1912) reports the association of gibbifer var. gibbosior with an unidentified pseudococcid that appears to be a Hippeococcus as well, probably H. rappardi, according to Reyne (1954). D. gibbifer nests in cavities in the ground and shows all characteristics of a typical herdsmen lifestyle, particularly a highly developed transport behaviour (the mealybugs actually ride on the ant's bodies). First indications of this highly developed mutualism, especially descriptions of the peculiar riding behaviour as well as descriptions of the nests, have been published by Buchner (1957), Franz (1975a+b), Jaconson (1912), Reyne (1954, 1965), and Van Der Goot (1930a+b).

In Java, the evergreen montane rainforests, the typical habitat of D. gibbifer, are restricted to the higher altitudes of the volcano massifs. Particularly in Eastern Java, these habitats may have been isolated for long periods of time by the deciduous monsoon forests of the lower altitudes, even without anthropogenic influences.

Nomenclature

 *  gibbifer. Dolichoderus gibbifer Emery, 1887a: 254, pl. 4, fig. 28 (w.) INDONESIA (Java). Combination in D. (Hypoclinea): Emery, 1894c: 229. Senior synonym of gibbosior: Dill, 2002: 45.
 * gibbosior. Dolichoderus gibbifer var. gibbosior Forel, 1912d: 108 (w.) INDONESIA (Java). Junior synonym of gibbifer: Dill, 2002: 45.

Worker
Dill (2002) - HL 1.18-1.39 [1.37]; HW 1.02-1.35 [1.25]; EL 0.26-0.32 [0.31]; SL 1.06-1.27 [1.19]; AL 1.56-1.97 [1.91]; PnW 0.70-0.89 [0.88]; ML 0.43-0.59 [0.55]; MW 0.31-0.41 [0.41]; PpL 0.65-0.82 [0.78]; PpW 0.53-0.65 [0.65]; PpH 0.45-0.63 [0.59]; PpSW 0.28-0.39 [0.33]; PtL 0.33-0.47; PtW 0.27-0.41 [0.39]; TL 4.78-5.74 [5.57].

Indices: CI 84-97 [91]; OI 24-27 [25]; SI 90-110 [95]; MI 133-158 [133]; PpSPpI 47-66 [52]; (n = 30).

Head: From brown to black. Entire head densely, ± evenly punctate (+ micro-imbricate, fig. III -61a); matt; usually with fine, golden pubescence (except frontal triangle); void of erect hairs. Head about as long as wide, suboval, widest just behind the eyes; occipital margin shallowly emarginate, sometimes with a very shallow median superoccipital pit.

Alitrunk; from brown to black. Finely reticulate-punctate (= micro-imbricate); usually, particularly at the sides (especially at mesopleuron) with ± parallel wrinkles in addition to the fine sculpturing (fig. III- 61b), these wrinkles very weakly developed in some populations (e.g. "gibbosior"-material from East Java); slightly shining, and scarcely pubescent; erect hairs very scarce and restricted to ventral surface and coxae. Sides of propodeum with fine, fingerprint-like, micro-imbricate, reticulate sculpturing, its declivitous face shiny, smooth to very finely reticulate. Dorsal face of pronotum in profile flat to convex; “shoulder” corners weakly and indistinctly developed. Mesonotum in profile forming a moderately to distinctly vaulted, rounded cone-like hump, which, in full face view, is not or only weakly impressed medially, and, in profile, distinctly flatter in the posterior portion; processes of mesopleuron weakly developed, usually only forming a flat hump; posterior margin of ascending dorsal face of propodeum distinct and sharp-edged, sometimes medially impressed (straight in types) (if so, lateral corners somewhat expanded to short, edged tips), and, in profile, not overhanging the declivitous face; thus, the latter immediately slopes down backwards from the posterior edge of the ascending face (fig. III- 10b); metapleural gland bullae strongly distended, and, if viewed from behind, laterally expanding much wider than the posterior edge of propodeum.

Petiole: Punctate (= micro-imbricate) and only scarcely pubescent; scale entire, its apical margin not concavely emarginate.

Gaster: Entire gaster densely punctate (= micro-imbricate); usually bearing a dense, golden-yellow pubescence (light-grey and less densely in the population from East Java [“gibbosior”]); particularly on 2nd and 3rd tergite, pubescence merging in a median line; erect hairs restricted to ventral face and gaster lip.

Queen
Dill (2002) - A single queen has been found in Java (Cibodas) after this manuscript has been finished. Therefore a complete morphological description could not be included. However, the queen is wingless with a large gaster and resembles in general the queens of the other species of the Dolichoderus cuspidatus group.

Type Material
Dill (2002) - Syntype workers, Java, Tcibodas (O. Beccari) [examined]; Java locality not specified] (Gribodo) (MCSN) [examined]; Java, Buitenzorg [Bogar] (Solms) [not examined]. One syntype here designated as Lectotype (MCSN).