Plaxes Pascoe, 1885

Prena, Jens, Hsiao, Yun & Oberprieler, Rolf G., 2023, New combinations and synonymies in the weevil genus Lyterius Schönherr (Coleoptera, Curculionidae), with a conspectus of historical works on Daldorff’s Sumatran beetles, Zootaxa 5380 (1), pp. 26-36 : 33

Plaxes Pascoe, 1885

The type species of Plaxes is P. impar , by monotypy. The collecting data of the type specimens given in the description are “ Sarawak, Doria ; Sungei Bulu (Sumatra), Beccari ”. Pascoe (1885) stated in the introduction that the specimens were sent to him by Giacomo Doria (1840–1913) and Raffaello Gestro (1845–1936) from the Museo Civico in Genoa. We located ten specimens of the original series in five museum collections (ANIC 1, MfNB 1, MSNG 5, NHMUK 2, SNSD 1). Pascoe seems to have retained one pair from Sumatra and one male from Sarawak (all in NHMUK) and replaced the original labels with blue lentiform discs stating the origin ( Fig. 8 ), but the female from Sumatra was later donated to Elwood C. Zimmerman (1912–2004) and, following his death, bequeathed to the ANIC. The MSNG has one male and two females from Sumatra and one pair from Sarawak, all with the pink printed locality label shown in Fig. 7 . The MfNB has one female from Sarawak with the same printed locality label, and the SNSD has one female from Sumatra with Faust’s handwritten label “Sumatra / Doria ”. The latter two stood unidentified in the unsorted material. The MfNB specimen is not recorded in the CGMZB, but Sarawak material obtained from Doria had been recorded as early as 1873 (CGMZB #57011–57027).

All six specimens of P. impar from Sumatra, collected by Odoardo Beccari (1843–1920), are conspecific with L. abdominalis , but the four from Sarawak are a different species. The original description of P. impar pertains to both included species (corpus infra piceum vel testaceum). Pascoe labelled his retained Sarawak male as the type of P. impar ( Fig. 8 ), and so did Doria with the Sarawak male returned to him ( Fig. 7 ; note Pascoe’s original label). These designations are unpublished and therefore invalid, and the species name thus lacks a single, name-bearing type. We consequently here designate a lectotype for Plaxes impar . Because the pair of syntypes in the MSNG has labels with more detailed information than the two in the NHMUK, we select as lectotype the male ( Fig. 3 ) with the following label data: “Borneo / Sarawak / 1865-66. / Coll. G. Doria ”, [handwritten by Pascoe] “ Plaxes / impar / ♂ ”, “174”, [handwrittEn by Doria ?] “ PlaxEs / impar Pasc. / typus!”, “ SYNTYPUS / PlaxEs / impar”, “MusEo Civico / di Genova”, “ LECTOTYPE / Plaxes impar / Prena et al. des. 2023” and “ Lyterius / impar / Prena det. 2023” ( Fig. 7 ). The other four returned specimens have the same syntype label but no original identification. We speculate that Doria and Beccari collected the four Sarawak specimens of the type series of P. impar during the first leg of their 1865–1868 expedition to Borneo, either in the surroundings of Kuching or en route to the Lupar estuary, before Doria fell ill and returned to Italy in March 1866 ( Viciani et al. 2021). The six Sumatran specimens of the type series of P. impar (ANIC 1, MSNG 3, NHMUK 1, SNSD 1), representing L. abdominalis , were collected by Beccari in September 1878 (MSNG, label data) at Sungei Bulu (“Bamboo River”), probably in the vicinity of Mount Singgalang in Padang, Western Sumatra. Faust (1896) identified a female of the L. abdominalis series as P. impar and described Plaxes dispar Faust, 1896 . Plaxes impar (as fixed herein) and P. dispar are exceedingly similar to each other, and more material is needed to ascertain whether the difference in the mesotibiae of the males signifies the existence of two distinct species or merely infraspecific variation, as occurs in another series from Sarawak ( Fig. 14 ).

Figures

FIGURES 6–8. Labels associated with first specimen of historical series. 6, Lyterius abdominalis in MfNB (original labels replaced in 1870); 7, Plaxes impar in MSNG (lectotype, see Fig. 3); 8, Plaxes impar in NHMUK (paralectotype, photograph by Keita Matsumoto).

FIGURES 1–5. Type species/specimens of Lyterius Schönherr, Plaxes Pascoe and Barisoma Motschulsky. 1, 2, paralectotype male and lectotype female of Rhynchaenus musculus Fabricius (ZMUK, Lund-Sehested Collection), type species of Lyterius; 3, 4, lectotype male and paralectotype female of Plaxes impar Pascoe (MSNG); 5, syntypes male and female of Barisoma pandanicola Motschulsky (ZMMU). Photographs 1–4 by Anne Mack (ZMUK), 5 by Vladimir Savitsky (ZMMU).

FIGURES 11–14. Sexual dimorphism and infraspecific variation in a series of three males and two females of a species near L. impar and L. dispar from Sarawak (donation of SMSM to SNSD by J. Hewitt in 1907). 11a, head of male with short, cuneiform rostrum; b, head of female with subcylindrical rostrum; 12a, anterior portion of pronotum of male with even surface; b, anterior portion of pronotum of female with subtle median longitudinal ridge; 13a, profemur of male with ventral tooth; b, profemur of female without ventral tooth; 14a, b, mesofemur of males with ventral tooth and infraspecific variation of mesotibia (two specimens with inner margin sinuous (a), one with abrupt basiventral protrusion (b)); c, mesofemur of female without tooth, mesotibia with inner margin nearly straight.