Memoirs of the Museum of Victoria 53(1): 125-128 (1992) 30 May 1992 https://doi.org/10.24199/j.mmv.1992.53.06 RHOPTROMYRMEX RAWL1NSONI SP. NOV., A NEW APPARENTLY WORKERLESS PARASITIC FROM ANAK KRAKATAU, INDONESIA (: FORMICIDAE: )

By Robert W. Taylor

Australian National Collection, CSIRO Division of Entomology. GPO Box 1700, Canberra, ACT 2601, Australia

Abstract

Taylor, R.W., 1992. Rhoptromyrmex rawlinsoni sp. nov., a new apparently workerless para- sitic ant from Anak Krakatau, Indonesia (Hymenoptera: Formicidae: Myrmicinae). Memoirs of the Museum of Victoria 53: 125-128. The alate-queen based Rhoptromyrmex rawlinsoni sp. nov. (Anak Krakatau I., Indonesia) is described and illustrated. It is presumed on morphological grounds to be a workerless parasite in the nests of another, unknown, ant .

Introduction On the basis of similarities to R. schmitzi and R. mayri the alate queen described here is pre- Rhoptromyrmex is a tetramoriine ant genus sumed to be a further workerless inquiline found comprising nine named species (Brown, 1964; normally in the nests of some other ant Bolton. 1986). Three occur in the Indo-Aus- species. tralian area: R. mayri (Forel) is known only from Given the circumstances of collection (from a India (Bolton, 1986), R. melleus (Emery) from flight-intercepting water trap) R. rawlinsoni is Sulawesi east to New Britain and northern Cape not certainly resident on Anak Krakatau. Its York Peninsula, and R. wroughtonii Forel from established presence somewhere in the Krakatau southern India eastwards to the Philippines, island group is reasonably assumed, despite the New Guinea and Cape York Peninsula (Taylor, proximity of Sumatra and Java, from which the 1991). type could have originated. Residence will be All known Rhoptromyrmex queens possess confirmed only by collection of a further speci- characteristics associated with social parasitism. men from a host colony. Their combinations establish the stages of an "anatomical parasitic syndrome" (see Wilson, Rhoptromyrmex rawlinsoni sp. nov. 1984 and Bolton, 1986, extending the hypo- theses of Brown, 1964). R. mayri and R. schmi- Figures 1-4 tzi (which is known only from Israel) are almost Type material. Unique holotype, collected on the workerless parasites of other certainly southwest shore of Anak Krakatau (06°66'S; 1 05°26'E), ( latinoda Roger and Tapinoma errati- Indonesia from a water trap set by members of the cum (Latreille) respectively). R. wroughtonii 1985 Krakatau Zoological Expedition, co-ordinated apparently disseminates by autoparasitism by Prof t.W.B. Thornton, La Trobe University, Mel- LW, and 31 followed by polygyny and colony fission. Other bourne. The label bears the numbers 21 1 latter in a small circle), and is dated 14-24/8/85. species, including R. melleus, have morphologi- (the Deposited in Research and Development Centre for cal characteristics implying colony foundation Biology, Bogor, Indonesia. The specimen has been by temporary social parasitism. gold coated for scanning electron microscopy. The not always morphologically Queens are detached wings are preserved in glycerin in an their presumptive characterised in keeping with attached microvial. reproductive/parasitic roles, and the workerless Description reproductive female. General fea- parasites are no more particularly distinctive of illustrated. Dimensions (mm) as follows: than some putatively autoparasitic or free-living tures as aggregate total length c. 2.7; head width (across forms. Reproductive females which are not eyes) 0.56; head length (maximum, including associated with conspecific workers, or those of clypeal projection) 0.59; scape length (maxi- an obvious host, thus often cannot be placed measurable chord length) 0.38; mesosoma confidently in the reproductive/parasitic spec- mum length (lateral view, direct measurement from trum.

125 126 R. W. TAYLOR A NEW ANT FROM THE KRAKATAUS 127 base of pronotal collar to posterolateral ex- half or so of petiole, essentially hairless. Anten- tremity of mesosoma) 0.72; pronotum width nae densely pilose, hairs shorter and finer than 0.42; petiolar node width 0.15; postpetiole elsewhere; legs similarly but less densely hirsute. width 0.26. Pubescence virtually absent. Mandibles subfalcate, masticatory margins Sculpturing little-developed except for few strongly oblique, each armed only with strong broken, concentric, semicircular striae behind apical tooth and small, reclinate, subapical den- the antennal insertions (Fig. 2), and scattered are relatively ticle; apical tooth aligned with main axis of pilosity-bearing punctures, which mandibular shaft, not down-turned. Antennae large on the frons, and finest on gaster and 12-segmented; scapes very slightly exceeding nodes; spaces between punctures almost every- occipital corners when appropriately pos- where strongly shining. Non-pilose areas speci- highly reflective, lacking itioned. Anteromedian border of clypeus greatly fied above smooth and extended to form broad, anterodorsally in- sculpturing. Propodeum less shining than somewhat irregularly clined, translucent tongue-like process (Figs 1, elsewhere, lightly and rugose. 2, 4). Palpal formula unknown (labio-maxillary golden-brown, complex of holotype retracted). General cranial General colour dull, medium darker. Mandibles, legs and proportions in full face view much as in R. gaster a shade concolorous, lighter golden- mayri, the eyes proportionately a little larger. clypeal process Occipital border shallowly concave at centre, brown. Hairs yellowish. Ventral out- occipital corners broadly rounded. Etymology. Named to honour the noted biol- in side view. Postgenae line of head concave ogist Peter Rawlinson who tragically died on longitudinally concave; 2 result- each shallowly Anak during the latest Australian Krakatau by broad, low, ing depressed troughs separated Expedition, April 1991. raised longitudinal tumosity centred at midline clypeal process, on genal suture (near-side concavity and raised N&tes. Apart from its distinctive postpetiole, R. rawlinsoni midline profile visible in Fig. 4). Mesosoma and the transverse R. schmitzi. It differs in simi- elongate and narrow, lacking notaulices; para- largely resembles from R. mayri, but that species has psidal lines vestigial. Posterodorsal propodeal lar fashion triangular mandibles. No modifications to the outline in profile a continuous, slightly convex generic diagnosis (Bolton, 1986) are curve. Propodeum unarmed, but with fine car- latest required, apart from mention of the clypeal pro- ina on each side running upwards from meta- cess described here. pleural lobe to about level of spiracle. Metapleu- Petiole in Workers identified as Rhoptromyrmex ral lobes barely raised, inconspicuous. wroughtonii have been taken (by the 1985 dorsal view narrow; nodal section only slightly on Anak Krakatau, making this broader than peduncle. Postpetiole quite expedition) species a possible host to R. rawlinsoni. strongly transverse. Petiolar node in profile as in R. keel rela- Several Rhoptromyrmex species, including fig. 4, not flattened above; subpetiolar transverse, melleus and the African species R. opacus Emery tively large. Subpostpetiolar process and R. tramversinodts Mayr, were considered by moderately large and acutely triangular in lateral the triangular, Brown (1964) to exhibit polymorphism in view; its anterior face approximately side. reproductive female. Each case depends on a slightly concave, submarginate on each presumption of conspecificity based on similar- Forewing veins extremely faint, especially several to R. ities among workers associated with the posteriorly. Venation reduced compared relevant female 'morphs'. It is equally plausible wroughtonii (as illustrated by Bolton, 1986); dis- m-cu); to assume non-conspecificity based on female coidal cell open apically (no cross-vein the existence of lacking. differences. This would imply radial cell closed; vein r-m + Mf Rhoptromyrmex species among which repro- Eyes bearing a few scattered, erect, fine hairs of ductive females are more easily distinguished with average length about twice diameter workers, and could challenge some current Dorsal surfaces of head, mesosoma than single facet. Also, pro- synonymies among worker-based taxa. (including sides of pronotum, and entire species might serve as hosts to alien con- nodes and gaster with abundant, long, some podeum), their own, nodes, gaster generic parasitic females similar to erect to suberect hairs; longest on be confused as conspecific with the and gaster ventrally with which could and frons. Postpetiole which Mandi- host workers in parasitized colonies (and similar but shorter and less-dense hairs. ight not be plausibly recognized as alien unless frons anterior to eyes, postgenae, m bles, clypeus, taken together and ventral queens of two or more kinds were sides of pronotum and mesothorax, 128 R. W. TAYLOR

in colonics). I suggest that current species-level Brown, W.L. Jr., 1964. Genus Rhoplromyrmex, synonymy in Rhoplromyrmex could be excess- revision of, and key to species (Insccta: Hymenop- ive, obscuring a greater underlying species rich- tera: Formicidae). Pilot Register ofZoology, Cards ness, and that workerlcss parasitic species might 1 1 to 1 9.

Taylor, R. W., 1 99 1 . Nomenclature and distribution of be more numerous than currently assumed. some Australasian ants of the subfamily Myrmi- cinae (Hymcnoptera: Formicidae). Memoirs of References the Queensland Museum 30 (3): 599-614.

Wilson, 1 984. Bolton, B., 19X6. A taxonomicand biological review of E.O., Tropical social parasites in the ant genus Pheidole, with an analysis of the anatomical t lie tetramoriine ant genus Rhoplromyrmex parasitic (I [ymenoptera: Formicidae). Systematic Entomo- syndrome (Hymcnoptera: Formicidae). logy II: 1-17. Insectes Sociaux 31: 31 6-334.