Pterapion Faust, 1889

Wanat, Marek & Munzinger, Jérôme, 2012, Biology of the Apionidae (Coleoptera: Curculionoidea) in New Caledonia, a preliminary report, Zootaxa 3554, pp. 59-74 : 64-66

Genus Pterapion Faust, 1889

This genus comprises four flightless species (one undescribed), all living in rain forest and oligophagous on a number of the Sapotaceae . The host plants all produce large seeds, likely where the larvae of Pterapion develop, judging from the observations of P. monstrosum (see below). Larval development (possibly also oviposition) apparently takes place in decaying fruits and seeds laying on the ground, not in the immature fruits on the plant. This would provide an explanation of the loss of functional wings and gigantism of Pterapion , which is completely unusual for typical seed-eaters living in fruits still growing on the plant. Freshly emerged beetles can be observed in almost every month, further confirming that larval food is available for a whole year, not only in the fruiting season of particular host plants. Hypertrophic abdomens of Pterapion might have also evolved as fat reservoirs for a long walks of the adult in search of the host plants which are often widely dispersed in the rain forest.

Although unable to fly, Pterapion species are all fast walkers and climbers of their arborescent host plants. Unlike most other weevils which easily fall down from the plant when disturbed, it is hard to force any Pterapion to come off the plant, even after touching the beetle with the frame of an entomological net.

Pterapion monstrosum Faust, 1889 . Two completely teneral specimens were obtained from seeds of Pycnandra canaliculata [15]. They had a relatively well sclerotised and hard head, rostrum, thorax and legs, with the narrow abdomen and elytra still completely soft and crumpled. Such disharmonious hardening of body helps immature beetle to leave its pupal chamber, which otherwise could be problematic for a beetle having so enormously inflated elytra. Another specimen was found piercing a cotyledon of a sprouting seed of Pycnandra canaliculata with its rostrum [16] ( Figs. 13, 14 ).

Adults were beaten from Beccariella sebertii and Pycnandra canaliculata (Sapotaceae) , but occasionally also from unrelated plants, e.g. repeatedly from Carpolepis laurifolia J.W. Dawson (J.W. Dawson) (Myrtaceae) . Although flightless, surprisingly hundreds of beetles were sampled in a Malaise trap in Col d’Amieu [17].

Pterapion kanalae Heller, 1916 . This large apionid (up to 13 mm long without rostrum) was repeatedly observed resting under broad leaves of Pycnandra balansae (Aoupinié Range) and P. comptonii (Mt Mandjélia) . The beetles, usually a few on one tree, were selectively attracted to the plants with freshly developed, whitish leaves, on which they occasionally fed ( Fig. 15 ). In November 2010, when the season of development of fresh leaves by the above-listed Pycnandra species was delayed due to low temperatures, adults of P. kanalae were collected in Aoupinié also from other species of Sapotaceae , like Pycnandra benthamii and Beccariella sp.

Pterapion wagneri Heller, 1916 . One of three peculiar New Caledonian apionid species with horned elytra (each of different genus), it is relatively common through Grande Terre. Adults are regularly collected from Beccariella rubicunda , Pycnandra balansae , and P. benthamii , likely living also on other Sapotaceae . Teneral specimens were recorded between 17 November and 29 June.

Pterapion sp. Several specimens of still unnamed species, including teneral ones (recorded through October to November), were collected from Beccariella lasiantha on the Poro Plateau, but one also from Pycnandra balansae in Koghi Mts.

Figures

FIGURES 9 – 14. Pupa of Megatracheloides bidentipes: 9) young in decayed flower bud of Hibbertia baudouinii, 10) the same soon before metamorphosis; 11) larva of M. cornutus in decaying flower bud of H. lucens; 12) larva of M. jourdani; 13, 14) Pterapion monstrosum piercing cotyledon of sprouting seed of Pycnandra canaliculata. (phot.: 9, 11 — MW, 10, 12 — S. Cazeres, 13, 14 — P. Lowry; sites: 11 — Koghi Mts, 12 — Nyamié creek, 9, 10, 13, 14 — Upper Rivière Bleue).

FIGURES 15 – 20. 15) Pterapion kanalae feeding on fresh leaf of Pycnandra balansae; 16) Aprotapion hamiota feeding on Codia incrassata; 16) feeding holes of Tetrapion n. sbgen. et sp. on C. incrassata; 17) adult of Tetrapion n. sbgen. et sp. feeding on inflorescence of C. incrassata; 18, 19) feeding holes of Tetrapion (s. str.) sp. on fresh stems and leaves of C. discolor. (phot.: all—MW; sites: 15 — Aoupinié, 16 — ca. 1 km NW Mt Mandjélia, 17, 18 — Mt Mandjélia, 19, 20 — Bois du Sud).