Prionopelta kraepelini Forel

Shattuck, S. O., 2008, Revision of the ant genus Prionopelta (Hymenoptera: Formicidae) in the Indo-Pacific region., Zootaxa 1846, pp. 21-34 : 23-26

Prionopelta kraepelini Forel

(Figs 3-7, 20)

Prionopelta kraepelini Forel , 1905: 3.

Types. Worker and queen syntypes from Tjompea, near Bogor, Java, Indonesia ( MHNG, examined).

Diagnosis. Sculpturing on dorsum of pronotum consisting of fine punctations which contrast markedly with widely spaced foveae on mesonotum and propodeum, the foveae on the propodeum varying in density across its width (weakest medially, stronger laterally). Head width less than 0.48mm. Petiole relatively narrow, PetW less than 0.21.

Description. Anterolateral corners of head, near mandibular insertions, rounded and lacking a tooth. Dorsal pronotal sculpturing consisting of fine punctations which contrast markedly with widely spaced foveae on mesonotum and propodeum. Foveae on dorsum of propodeum varying across its width (weakest medially, stronger laterally). Lateral mesosomal sculpturing consisting of small foveae on pronotum and anterior and ventral region of mesopleuron, dorsal region of mesopleuron and majority of propodeum smooth. Fenestra generally present but sometimes weakly developed within subpetiolar process. Colour pale yellow to yellow-red.

Measurements. (n=13) CI 74-80; HL 0.45-0.49; HW 0.33-0.38; ML 0.50-0.60; PetL 0.12-0.15; PetW 0.18-0.21; PI 131-154; SI 66-73; SL 0.24-0.27; T 1W 0.28-0.32.

Material examined (in ANIC unless otherwise noted). Caroline Islands: Palau Islands: NW Auluptagel (Gressitt,J.L.); Truk Islands: Mt. Teroken, Moen Island (Gressitt,J.L.); Yap Group: Dugor, Yap Island (Goss,R.J.); Kanif, Yap Island (Goss,R.J.); N Yap Island (Goss,R.J.). Samoa: Upolu: Apia (Ettershank,G.; Taylor,R.W.) ( ANIC, MCZC); Napanua (Maddison,P.A. & Light,M.V.); Vaivasi/Vaivase (Lidgard,W.; Maddison,P.A.; Taylor,R.W. & Lidgard,W.) ( ANIC, MCZC); Viala (Taylor,R.W.) ( ANIC, MCZC). Indonesia: Banten: Palau Peucang (Harvey,M.S.); Central Sulawesi: Palolo, Palu, C.Celebes (Yasunaga,T.); North Sulawesi: Dumoga-Bone Nat'l Park (Kistner,D.H. & Roche,D.F.); Utara, Dumoga-Bone NP (Horak,M.); Sumatra: Lake Toba, Samosir Is. (Jaccoud,T. & Marcuard,P.); West Java: Buitenzorg (Kemer,N.A.) ( MCZC). Malaysia: Perak: Sungei Simei Falls, Cameron Highlands (Jaccoud,T. & Marcuard,P.); Sungei Simei Falls, Cameron Highlands (Jaccoud,T. & Marcuard,P.); Sabah: mi.45 Labuk Rd. ex. Sandakan (Lungmanis) (Taylor,R.W.); Sepilok For. Res. nr. Sandakan (Taylor,R.W.); Tawau, Quoin Hill (Taylor,R.W.); Sarawak: Kampong Segu, 20mi. SW Kuching (Taylor,R.W.); Kampong Segu, 20mi. SW Kuching (Taylor,R.W.). Philippines: Luzon: Mt. Makiling (Baker,C.F.) ( MCZC); Negros: Dumaguete (Chapman,J.W.; Empeso,D.) ( MCZC); Old Cemetery, Dumaguete (Empeso,D.) ( MCZC); Quezon: Quezon City, Ateneo de Manila (Lowery,B.B.).

Comments. This is one of the most widely distributed species in the genus, being found from Sumatra and Peninsular Malaysia east through the Philippines and Micronesia to Samoa. Most specimens have been collected from leaf litter samples in forested areas (mainly rainforests but including parkland on volcanic soil). It should be noted that the Samoan population is a considerable outlier and is somewhat unexpected given that the range of P. opaca is much closer to Samoa than the main range of P. kraepelini . Unfortunately the currently available Samoan material is limited to queens, and while these queens are morphologically similar to P. kraepelini it is possible that this population belongs to a distinct species. The discovery of workers will help confirm the true identity of this population.

Taxonomically, Brown (1960) confused this species with P. opaca and didn't recognize the specimens here placed in P. robynmae as belonging to a separate species. In fact, all three of these species, while morphologically similar, can be separated as follows. In true kraepelini the sculpturing on the pronotum consists of small, fine punctures which contrast strongly with the widely spaced foveae on the mesonotum and propodeum(Fig. 5). In opaca the pronotal sculpturing is composed of widely spaced foveae which are only slightly more dense than those on the mesonotum and propodeum (Fig. 18). And in robynmae the sculpturing consists of small foveae on the pronotum which contrasts markedly with the widely spaced foveae on mesonotum and propodeum (Fig. 19). In addition, the density of the sculpturing across the width of the propodeum is variable (weakest medially, stronger laterally) in kraepelini and robynmae and uniform in opaca . The shape of the petiolar node also differs across these species. It is narrowest and shortest in kraepelini , relatively longer and broader in opaca and long but narrow in robynmae (Fig. 6). Essentially all presently known material can be unambiguously sorted into three sets representing these three taxa based on these character systems. In all other respects the material of these taxa is essentially identical or the differences are slight and random and show no obvious patterns. While kraepelini is allopatric to the others, opaca and robynmae have been collected together (from the same litter sample) in PNG.

The only apparent exception to this pattern is a single collection from Palolo, Palu, C. Celebes, Indonesia. In these specimens, the punctations on the propodeal dorsum are somewhat intermediate between kraepelini and opaca , although they are more similar to typical kraepelini than typical opaca . This is consistent with other material from Sulawesi which is typical of kraepelini . A reexamination of Brown's Micronesian material has failed to uncover his "intergradient" forms as all could be placed with confidence into kraepelini , opaca or robynmae .