Polyrhachis schellerichae

The biology of this species was investigated in Selangor, West-Malaysia. It was found nesting in culm internodes of giant bamboo (Bambusoidea: Gigantochloa thoii). The investigated colonies were polydomous, diurnal and lived in tight trophobiosis with pseudococcids, Kermicus wroughtoni, which were kept inside the nest internodes. The trophobiotic partners were transported to new nest internodes during colony enlargement or nest moves. A series of specific morphological and biological features indicate that this ant is specialized on living within giant bamboo culms. (Schellerich-Kaaden et al. 1997)

Identification
Dorow (1997) - A member of the Polyrhachis hector species group, which is characterized by its flattened tibiae and antennae. The new species can be easily distinguished from all other Polyrhachis by its strongly elongated head, especially in the female.

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

Biology
Schellerich-Kaaden et al. 1997 - Two colonies were studied at the Ulu Gombak Station(30 km northeast of Kuala Lumpur, 240-500 masl). One complete colony was nesting in 47 bamboo culms (1-6 internodes per inhabited culm), with 7203 workers, 605 alate queens and 1310 males. Nest entrances were typically a single oval opening, which were always guarded by one or several workers. Cocoons were fixed to the walls of internodes using silk but silk was not used to line their nests or modify their nest entrances.

, a mealybug (Pseudococcidae), were found in every inhabited internodes (one internode checked contained 188 crawlers and 10 adults). Trophobionts were observed being carried between internode nests. When a suitable new internode was located by scouts, only mealybug crawlers (first instar larvae) were transported. When new colonies are founded, horizontal transmission of the mealybug partners is likely, unlike Tetraponera attenuata where foundresses fly while carrying a gravid Kermicus wroughtoni.

Foraging was diurnal and carried out individually. During rain activity generally dropped to zero. Vertebrate faeces were carried from the ground into the nest, but no predation or scavenging was observed and the honeydew excreted from the scale insects inside the nest is presumed to be the main source of nutrition in P. schellerichae. Workers with dilated gasters (i.e. with honeydew) were observed walking between internodes. Interactions showed this species to be subordinate and would readily move away from other ant species (e.g. Polyrhachis arachne) it encountered. Recruitment behavior and the use of trail pheromones were observed in laboratory tests with food but these were likely used more for relocating nests and maintaining movement between nests.

Most of the workers leaving a nest did not forage but hurried without any delay to other nest internodes. Traffic between the partial nests was accomplished via distinct routes up and down the culm. Neighbouring culms were connected through routes on the ground and presumably through routes in the canopy of the culms over branches and leaves which often are in very close contact. Transport of brood and mealybugs to partial nests was also observed.

Polyrhachis schellerichae nests inside the culm internodes {mean length 42.66 ± 11.49 cm, n = 42; mean diameter 8.11 ± 1.65 cm, n = 40). The interior of all investigated nest internodes (n = 63) was neither covered with silk nor modified in any other way. Larval silk was only used to attach the brood to the internode walls. In case of disturbance the workers detached the threads and carried the brood away. The pupae of P. schellerichae have cocoons. An occupied culm internode had usually one oval nest entrance (length 2.0- 15.0 mm; width 1.0-6.0 mm; n = 11). Only exeptionally more than one nest entrance (up to three) per nest internode could be observed. The nest entrances of P. schellerichae were always guarded by one to several workers depending on the size of the hole. During rain the number of guarding workers at the nest entrances increased. Their heads blocked the nest entrance from inside and thus apparently prevented influx of rain water into the nest. The head of P. schellerichae, especially that of the queen, is remarkably elongated.

If a suitable new internode was located by scouts of an opened nest the relocation was completed in relatively short time (1.5 and 3 h, n = 2). Whereas males were carried, alate queens and workers walked independently to the new nest. The males were seized in the neck and carried in front of the worker. Only once a worker was carried. It was held by the mandibles in the typical formicine way with its body under the head of the carrying worker. The nest relocations followed no fixed time pattern. Males and brood were carried during the whole time. The alate queens walked either by themselves amidst a group of workers or individually without accompanying workers. Workers carrying trophobionts to the new nest-site were observed in five cases during two nest relocations. Only crawlers (1st instar larvae) were carried and only a fraction of the crawlers of the original nest was transferred to the new nest-site. All new nest internodes contained living trophobionts when they were opened a few days later (n = 4). As these crawlers sat on the internode walls in the same way as the others left behind in the old nest internode we concluded that they were not taken as prey but as trophobiotic partners instead. Under natural conditions in the field we also observed this pseudococcid carried by P. schellerichae between partial nests in two cases. These transports were not connected with nest relocation.

Nomenclature

 *  schellerichae. Polyrhachis (Myrmhopla) schellerichae Dorow, 1996b: 122, figs. 1-14 (w.q.m.) WEST MALAYSIA. See also: Schellerich-Kaaden, Dorow, et al. 1997: 77.

Worker
Holotype. TL: 9.47; HL: 2.43; HW: 1.41; SL: 2.18; TPL: 3.84; GL: 3.20; G1L: 1.41; G1W: 2.05; MTL: 3.58; PW: 1.02; PNSW: 1.66; PPSW: 0.64; PTSW: 1.28; PTL: 0.64; WL: 3.07; CI: 57.89; SI: 154.55.

Worker (n = 20): TL: 8.72-9.79 [9.29 ± 0.25; 9.29]; HL: 2.18-2.44 [2.38 ± 0.07; 2.41]; HW: 1.25-1.41 [1.34 ± 0.05; 1.34]; SL: 2.18-2.32 [2.22 ± 0.05; 2.20]; TPL: 3.46-3.97 [3.74 ± 0.12; 3.78]; GL: 2.70-3.71 [3.17 ± 0.22; 3.78]; G1L: 1.15-1.47 [1.31 ± 0.08; 1.28]; G1W: 1.68-2.18 [1.95 ± 0.11; 1.92]]; MTL: 3.33-3.71 [3.53 ± 0.10; 3.56]; PW: 0.90-1.02 [0.96 ± 0.05; 0.96]; PNSW: 1.38-1.68 [1.52 ± 0.10; 1.54]; PPSW: 0.37-0.77 [0.57 ± 0.10; 0.55]; PTSW: 1.16-1.38 [1.27 ± 0.05; 1.28]; PTL: 0.61-0.74 [0.66 ± 0.03; 0.64]; WL: 2.88-3.20 [3.07 ± 0.09; 3.07]; CI: 54.05-57.89 [56.24 ± 1.21; 56.09]; SI: 154.55-177.23 [166.24 ± 6.67; 167.63].

Head elongately oval; mandibles with 5 very broad and coarse teeth, gradually increasing somewhat in size from base to tip of mandible; mandibles finely longitudinally striate with small hair-pits; maxillary palps barely reaching the frontal margin of the eyes when flexed back against the genae; frontal margin of clypeus weakly convex, central two thirds weakly protruding with lateral corners, this area shiny with larger hair-pits; rest of clypeus finely punctured, with a weak central keel which is moderately shiny and bears only very few hairs; eyes positioned in the upper half of the head, without hairs, in frontal view rising moderately above the outline of the head; genae in frontal view long, convex, not marginate; occiput marginate; ocelli lacking; temples nearly parallel, only weakly narrowing posteriorly, with weak lobes at the posterior corners; antennae with flattened short (compared to other Polyrhachis species) scapes, which are protruding above the occiput by about 1/ 3 of their length; antennal segments longest near the scape; frontal carinae flat and only weakly curved, with a weak moderately shiny central keel.

Alitrunk long and slender, widest at the pronotum, not marginate; pronotum in side view convex, anteriorly with 2 long and acute spines that protrude forward, a little upwards and sideways, their tips weakly curved down; mesonotum in side view saddle-like concave; propodeum in side view straight, on top with 2 long and acute spines that are directed backwards and only weakly upwards and sideways; propodeal spines running forward on the upper sides of the segment in a bulge-like manner; posterior part of propodeum declining concavely to the petiole; metathoracic spiracle round; propodeal spiracle a vertical oval slit with a median constriction; pronotal-mesonotal suture distinct; mesonotal-propodeal suture indistinct, elevated on a bulge; area where in other ant genera the metapleural gland bulla is situated sometimes coloured light brown, always smooth and shiny; legs long and slender, tibiae flattened without rows of spines; tibial spur comb-like.

Petiole short and broad, in side view with a nearly ball-like appearance (anteriorly and posteriorly convex) and broadly inserting long spines on top which are curved backwards and at the most slightly upwards, nearly embracing the gaster; spiracle of petiole round; ventral side with a keel anteriorly, which begins with a steep incline and runs arched to the posterior end of the segment.

Gaster elongately oval; first segment anteriorly with a short ascent, which is at its lower part more or less straight and only at its upper part convex; all segments close to their posterior margins with a row of scattered hairs which are directed obliquely backwards; acidoporus only anteriorly with a row of short bristles, this row interrupted in the middle, the bristles closest to the resulting gap the longest; anterior-ventrally with a short process protruding anteriorly below the joint of the petiole.

Sculpture: head and alitrunk with fine pits, which are of the areolate type (HARRIS 1979), petiole and gaster with a fingerprint-like sculpture, this type of sculpturation is not figured in Harris (1979).

Hairs: whole body with a fine, dispersed, loosely appressed pubescence which is not hiding the sculpture.

Glossiness and colour: head in front of the eyes and gaster of a weak, silky glossiness, posterior part of head and alitrunk more or less matt; head including mandibles and alitrunk black to blackish-brown, gaster a little lighter (chestnut brown), legs chestnut or dark brown, tarsi blackish; antennae blackish-brown, becoming lighter towards the tip, tip of last segment yellowish-brown; eyes matt pink to blackish red.

Queen
(n = 20): TL: 12.62-13.57 [13.05 ± 0.26; 13.06]; HL: 3.33-3.58 [3.47 ± 0.07; 3.46]; HW: 1.41-1.60 [1.48 ± 0.06; 1.48]; SL: 2.19-2.43 [2.37 ± 0.06; 2.38]; TPL: 5.17-5.50 [5.33 ± 0.09; 5.38]; GL: 3.97-4.86 [4.26 ± 0.22; 4.22]; G1L: 1.41-1.79 [1.58 ± 0.09; 1.56]; G1W: 2.05-2.55 [2.24 ± 0.12; 2.30]; MTL: 3.78-4.10 [3.93 ± 0.08; 3.91]; PW: 1.23-1.41 [1.32 ± 0.04; 1.32]; PNSW: 0.64-1.02 [0.90 ± 0.08; 0.90]; PPSW: 0.40-0.51 [0.45 ± 0.04; 0.45]; PTSW: 0.81-0.91 [0.87 ± 0.03; 0.88]; PTL: 0.70-0.96 [0.78 ± 0.06; 0.77]; WL: 4.35-4.67 [4.50 ± 0.08; 4.48]; CI: 40.44-46.30 [42.71 ± 1.86; 42.14]; SI: 149.60-172.73 [160.41 ± 6.50; 158.33].

Female differing strongly from the worker. Head very long, in frontal view nearly rectangular, with the margins near the eyes weakly concave, in side view long and slender; mandibles with 5 teeth, gradually increasing somewhat in size from base to tip of mandible, but with the penultimate one being the smallest, finely longitudinally irregularly striate with fine hair-pits and loosely dispersed hairs; maxillary palp when flexed back against the gena not reaching the frontal margin of the eye; eyes blackish or reddish, situated in the upper half of the head, only weakly convex and only slightly breaking the outline of the head, without hairs; clypeus as in the worker, but posteriorly ending in an irregularly shaped dent, a larger hair pit is situated to each side of the dent, these two hair pits are often not positioned in symmetric distances from the dent; 3 ocelli; genae very long (about 1.8 mm), nearly straight (weakly convex), not marginate; temple about 1.1 mm long, temples in full face view running parallel to each other, i. e., head not narrowing at occiput; each side of posterior end of head protruding in a swelling; occipital margin concave, rounded; antennae with flattened short scapes which are widest closely in front of the posterior end; protruding beyond the occiput by less than 1/3 of their length; distal segments of funiculus shorter than proximal ones, only the last segment of about same size as the first; frontal carinae flat, only weakly curved, i. e., nearly parallel to each other, with a weak central keel between them, running nearly to the first ocellus, area between frontal carinae anteriorly only weakly sculptured and strongly shiny, posteriorly of the usual sculpture of the head (see below).

Alitrunk in side-view and in top view long and slender, nearly parallel sided, without margination, relatively flat on top; sutures distinct but never built as furrows; pronotum anteriorly only with a tubercle or angle on each side; mesonotum very long, in side-view the central part straight or weakly concave, anteriorly the segment has a steep rise, which shows a weak central keel; a U-shaped keel runs on the posterior half of the top of this segment (opening anteriorly); propodeum in side-view nearly straight, with swellings or short teeth where spines are present in the worker caste; decline to the petiole low and concave; metathoracic spiracle very small and round, propodeal spiracle large and oval as in the worker; femora, tibiae and first tarsal segments flattened; tibiae without rows of spines; tibial spurs pectinate; fore wings light greyish brown, stigma and veins dark brown, in front of the stigma a small colourless area, also the folding line of the wing colourless; hind wings without such colourless areas, veins anteriorly darker brown in most specimens, a row of 17-19 hooks begins at the anterior margin of the hind wing posteriorly from where the cross vein meets the subcosta.

Petiole as in the worker, but on top at each side a spine (much shorter than in the worker) with a broad base arises, running backwards, weakly upwards and only very weakly outwards; area between the two spines broad and rounded.

Gaster like in the worker caste.

Sculpture similar to that in the worker caste, but generally somewhat weaker, much weaker and more shiny on top of mesonotum, imbricate (Harris 1979) on petiole; coarser pairs of pits near the anterior and posterior borders of the clypeus, near its side corners and near the anterior sides of the frontal triangle; a single pit at the posterior end of the frontal triangle, where the antennal keel starts; area where in other ant genera the metapleural gland bulla is situated sometimes coloured light brown and shiny.

Hairs: few yellow-brownish hairs on clypeus, coxae, keel of petiole, posterior ends of femora, tibiae, tarsal segments and gaster (as described above); first gaster sternite centrally also with few hairs; palps with hairs, antennal segments especially posteriorly with short bristle-like erect hairs; whole body with a fine, weak, appressed whitish pubescence, which does not hide the sculpture but is somewhat stronger on coxae and gaster.

Glossiness and colour: whole body with a weak silky glossiness, mesonotum and head (except the part above the eyes in full face view) more shiny than rest of body; whole body black to blackish brown, palps, tip of last antennal segment, tip of last tarsal segment, tip of last gaster segment and strigil yellowish brown, gaster blackish brown to black, posterior margins of segments, especially of sternites, often lighter. One specimen had a round brownish-yellow area on the third gaster tergite, with a central injury in the middle. The cause for this injury could not be evaluated, but it is known, that parasitic infections often change body colours to lighter shades.

Male
(n = 20): TL: 7.94-9.22 [8.45 ± 0.30; 8.43]; HL: 1.47-1.60 [1.52 ± 0.03; 1.54]; HW: 0.95-1.02 [0.99 ± 0.03; 0.99]; SL: 1.41-1.60 [1.47 ± 0.05; 1.47]; TPL: 3.71-4.10 [3.96 ± 0.10; 3.97]; GL: 2.56-3.71 [2.96 ± 0.25; 2.94]; G1L (n = 8): 1.02-1.15 [1.08 ± 0.05; 1.07]; G1W (n = 4): 1.45-1.79 [1.58 ± 0.14; 1.54]; MTL: 2.55-2.69 [2.62 ± 0.04; 2.62]; PW: 1.14-1.59 [1.33 ± 0.12; 1.29]; PTL: 0.50-0.59 [0.54 ± 0.03; 0.52]; WL: 3.01-3.52 [3.34 ± 0.12; 3.36]; CI: 61.67-68.97 [64.85 ± 1.69; 64.66]; SI: 137.50-168.92 [148.87 ± 8.43; 148.03].

Head oval in frontal view, semicircular in side-view; clypeus convex, weakly keeled along its midline, anterior border convex and with a few long setae; eyes large, situated slightly above the middle of the sides of the head, nearly hemispherical, breaking the outline of the head, reddish-black, without hairs; genae about as long as the eyes, straight, not marginate; temple about as long as the eyes, somewhat narrowing towards the occipital margin, but occipital margin still broad and nearly straight, only weakly concave due to weakly prominent side corners; 3 large ocelli protruding in a hump-like way; mandibles only with one broad based anterior tooth, rounded behind this tooth after a notch; palps when flexed backwards protrude to the anterior border of the eyes; antennal scapes protruding beyond the posterior margin of the head by about half of their length; scapes without distinct flattening, colour of underside of antennal segments in some specimens becoming lighter toward the tip, where they are yellowish; frontal carinae flat, the sides at most weakly curved upwards, only weakly curved above the insertions of the antennae, weakly shiny; area between them with a weak central keel; sometimes an indistinct groove is present in front of the first ocellus.

Alitrunk proportions similar to those of female, but overall appearance shorter and broader (broadest in front of the wings); pronotum and anterior part of mesonotum form a vertical incline of the alitrunk; mesonotum in this part with two sutures, which start apart from each other in the lower area, then approach each other and finally often run parallel to each other to the top of the incline, after a short interruption a central suture running along top of the segment for about 1/3 of the segment's length; about at the height of the central suture's end, a lateral suture at each side of the upper part of the mesonotum starts running backwards to the end of the segment; mesonotum in side-view on top nearly straight (weakly convex), not saddle-shaped; scutellum strongly arched; propodeum convex, running evenly down to the insertion of the petiole; alitrunk without margination or spines, propodeum sometimes with small humps at where the spines are situated in the workers; sutures distinct but not incised; metanotum higher than propodeum, posteriorly elongated in the middle; metathoracic spiracle like a small round puncture; propodeal spiracle large and oval; wings like in the female, but lighter areas indistinct; fore femora somewhat flattened, other parts of legs not; only fore tibiae with a distinct spur (strigil).

Petiole nodiform, sometimes weakly marginate or humped posteriorly at the sides; ventral part of petiole with a weak keel, which is evenly arched anteriorly and posteriorly.

Gaster slender; first segment short, weakly increasing in diameter, otherwise like in the female.

Hairs and pubescence like in the female but petiole with erect light hairs.

Sculpture similar to that in the female but frontal head sculptured like the rest of the body; sculpture on gaster imbricate (Harris 1979).

Glossiness and colour: head and alitrunk of a weak silky glossiness, gaster more shiny; colour lighter than in female.

Sexual organs: sagitta, volsella, stipes posteriorly brownish, anteriorly yellowish brown, sagitta sometimes totally yellowish brown; only stipes posteriorly with standing light hairs.

Type Material
Holotype: Worker (SMF 2369), Malaysia, Selangor: Ulu Gombak Research Centre, 8.III.1992; Angela Schellerich, Acc.No. 15.34.6.

Nidoparatypes: 350 workers (SMF 2370), 47 alate and none dealate females (SMF 2371), 91 males (SMF 2372), and uncounted numbers of pupae in cocoons, larvae and eggs.

Paratypes: 161 workers (SMF 2373), 29 females (SMF 2374), 40 males (SMF 2375), and uncounted numbers of pupae in cocoons, larvae and eggs, same locality as holotype, 6.II.1993; A. Schellerich, Acc.-No. 21.14.3.

Nidoparatypes and paratypes in the following collections: Senckenberg-Museum, Frankfurt a.m.; The Natural History Museum, London; Austral. Natn. Insect Coli., Canberra; Forest Res. Inst. Malaysia, Kepong; Univ. Mus. Kuala Lumpur; Mus. comp. Zool. Harvard Univ.; Queens. Mus., Brisbane; Coil. U. Maschwitz a.w. Goethe-Univ., rankfurt a.M.); Coli. A. Schellerich.



Etymology
The species is named after its discoverer, Miss Angela Schellerich.

Determination Clarifications
P. sp. no. 3 in Dorow 1995.