Platytenes Pascoe, 1870

Setliff, Gregory P. & Larson, Peter A., 2009, The Indo-Australian weevil genus Platytenes Pascoe, 1870 (Coleoptera: Curculionidae: Cryptorhynchinae), Insecta Mundi 2009 (79), pp. 1-14 : 2-3

Platytenes Pascoe

Platytenes Pascoe, 1870: 466

Platystenes Pascoe [error in Heyden 1911]

Type species: Platytenes varius Pascoe, 1870: 467 by monotypy.

Bibliography. Pascoe 1870: 467 [original description], plate XVIII, figure 1 [figured]; Gemminger and Harold 1871: 2561 [catalog]; Pascoe 1885: 269 [distribution records: New Guinea]; Masters 1888: 940 [catalog]; Faust 1899: 65 [distribution records: New Guinea]; Heyden 1911: 362, 371 [distribution records: Aru and Kei Islands]; Lea 1913: 276 [redescription; distribution records: Australia; discussion of relationships]; Heller 1929: unpaginated table [distribution records: New Guinea]; Marshall 1935: 46 [distribution records–Sulawesi]; Hustache 1936: 247 [erroneously synonymized with Chaetectorus (= Chaetectetorus ), see discussion of taxonomy below], Heller 1941: 217 [removed from synonymy and diagnosed from Chaetectetorus , see discussion of taxonomy below]; Marshall 1952: 269 [removed from synonymy with Chaetectetorus , see discussion of taxonomy below]; Voss 1958: 219 [distribution records: New Guinea]; Bigger and Schofield 1983: 30, 34, 42 [checklist; distribution records: New Guinea and the Solomon Islands; Solomon Islands record attributed to P. varius most likely refers to our new species]; Zimmerman 1992: 310, plate 459 figures 5 and 6 [figured]; Alonso-Zarazaga and Lyal 1999: 127 [catalog]; Setliff 2007: 109 [checklist].

Recognition. A most unique and diagnostic feature for Platytenes is their large and unusually shaped metepisternites ( Fig. 8 , 16 ). The anterodorsal margin is strongly produced dorsad from the apex to about mid-sclerite. The adjoining portion of the elytron (anapleural margin) bears a semicircular recess to accommodate the enlarged margin of the metepisternite. While this character alone is sufficient to diagnose the genus, the following characters include more readily observable features that will also aid in separating Platytenes from other weevil genera. The dorsum is nearly flat ( Fig. 2–8 ) with four fasciculate tubercles near the anterior margin of the pronotal disk ( Fig. 14–15 ). The elytral humeri are strongly produced making the elytra 1.3–1.5 times broader than the pronotum. The rostrum is very narrow, almost straight or very weakly curved, and glabrous in both sexes past the point of insertion of the antennae. The antennae are inserted in the basal one-third of the rostrum. The scape is very short, being only as long as the club, and does not reach the eye ( Fig. 11 ). The dorsal vestiture is comprised of densely distributed, mottled black, white, and tan scales arranged in a highly variable pattern even among sympatric specimens; however the elytral declivity to the apex is entirely clothed in white to cream colored scales in all specimens we examined. Fig. 2–7 illustrate variation in dorsal vestiture among and between Platytenes species. Sclerolepidia are not visible and are probably absent. The hind femora also are clothed characteristically with the basal one-third bearing white to cream colored scales and the distal portion black as in Fig. 8 . The venter, like the dorsum, is more or less flat. Female terminalia provide a further diagnostic, generic-level character. The apex of tergite VIII is abruptly and strongly curved ventrad so that it is orientated nearly 90 o from the rest of the tergite. The apex is simple, lacking stout setae or crenulations, and is strongly bifurcate ( Fig. 28–29 ).

Taxonomy. For nearly two decades, Platytenes was considered a junior synonym of Chaetectetorus Schönherr due to an error in the Coleopterorum Catalogus. Hustache (1936: 247) erroneously synonymized Platytenes with Chaetectetorus (misspelled Chaetectorus in that work), apparently due to his misinterpretation of comments made by A. M. Lea (1913: 276). However, Lea did not propose any such synonymy in his work; rather he simply suggested a distant affinity between the two genera. Heller (1941: 217) was the first to recognize and attempt to rectify Hustache’s mistake. Unfortunately, Heller’s correction appeared as a short statement preceding the description of Chaetectetorus cinereus Heller , in a paper on the weevils of New Britain where Platytenes was not yet known to occur. Consequently, his correction was overlooked by subsequent workers. More than a decade later, Marshall (1952: 269) published a second correction in a brief note. Despite these two published corrections, we have seen specimens of Platytenes still arranged in Chaetectetorus in some collections, indicating that confusion over the validity of Platytenes persists.

Ecology and Biogeography. Little is known of the habits of these relatively common weevils. The following comments are based primarily on label data from the material we examined. Platytenes species appear to be restricted to low to mid-elevations (0–700 m above sea level [a.s.l.]) with most specimens we examined occurring between 0–200 m a.s.l. Like most cryptorhynchines, adults of Platytenes species are poor flyers (Setliff, personal observation), and we presume that they have limited dispersal ability. Despite this apparent limitation, Platytenes species have an unusually broad distribution compared to other cryptorhynchines from the region. Label data provide one plausible explanation. Several specimens of two Platytenes species were collected on semi-cultivated betel palm ( Areca catechu L., Arecaceae ). Although the betel palm likely originated in Southeast Asia, archaeobotanical evidence suggests that the stimulant betelnut has been chewed throughout Melanesia for 3000–5000 years ( Fairbairn and Swadling 2005, Zumbroich 2007). The putative association between Platytenes and A. catechu , combined with the atypical distribution and presumed poor dispersal ability of the weevils suggests human mediated dispersal may have played a role in the present-day distribution of Platytenes species. To our knowledge, no specimens have been reared from betel palm; however, larvae are capable of developing in other host plants. Two adults of P. varius in GPSC were reared from wood of Ficus nodosa Teijsm. and Binn. (Moraceae) and one adult was reared from Nauclea orientalis (L.) L. ( Rubiaceae ).

Distribution. ( Fig. 1 ). Moluccas (= Maluku Islands), Aru Islands, Kei Islands, Waigeo Island, New Guinea, D’Entrecasteaux Islands, Bismarck Archipelago, Australia and the Solomon Islands.

Figures

Figure 1. Distribution of Platytenes species. Squares = Platytenes varius; circles = Platytenes occultus. Localities are from the literature and material examined in the present study. The specific location for P. varius in northern Queensland, Australia could not be verified.

Figure 8–11. Platytenes species. 8–9) Platytenes occultus, holotype, male habitus. 8) Lateral view. 9) Ventral view. 10–11) Detail of male pronotum, lateral view. 10) Platytenes occultus, paratype. 11) Platytenes varius.

Figure 14–18. Platytenes species. 14–15) Dorsal outline of pronotum, broken lines indicate position of fasciculate prominences and raised medial area. 14) Platytenes occultus. 15) Platytenes varius. 16) Platytenes occultus, meso- and metapleura, lateral view, broken line indicates bent portion of mesepimeron; key: c2–c3. meso- and metacoxae, ely. left elytron, epm2. mesepimeron, eps2. mesepisternum, eps3. metepisternum, r. lateral wall of mesosternal receptacle, s2–s3. lateral portion of meso- and metasternites. 17–18) Left hind femur and tibia, anterior (outer) view. 17) Platytenes varius, arrow indicates flange. 18) Platytenes occultus. Scale bar = 1 mm.

Figure 2–7. Platytenes species, dorsal habitus. 2) Platytenes varius, male (Jayapura, West Papua, Indonesia). 3) Same, female (Ambon Island, Indonesia). 4) Same, male (Finschhafen, Papua New Guinea). 5) Platytenes occultus, holotype, male (Guadalcanal, Solomon Islands). 6) Same, paratype, female (Guadalcanal, Solomon Islands). 7) Same, paratype, female (Ugi, Solomon Islands).

Figure 19–34. Platytenes species. 19–22, 25–27) Platytenes occultus, male terminalia. 19) Spiculum gastrale, ventral view. 20) Tergite VIII and sternite VIII, ventral view. 21) Aedeagus (tegmen removed), lateral view. 22) Aedeagus, dorsal view. 25) Tegmen, ventral view. 26) Tegmen, lateral view. 27) Tergite VII, dorsal view. 23–24) Platytenes varius, aedeagus (tegmen removed). 23) Lateral view. 24) Dorsal view. 28–34) Female terminalia. 28) Tergite VIII, dorsal view. 29) Tergite VIII, lateral view. 30) Sternite VIII, ventral view. 31) Sternite VIII, lateral view. 32) Tergite VII, dorsal view. 33) Hemisternites, dorsal view. 34) Spermatheca. Scale bar = 0.5 mm.