Megatracheloides Lucas, 1920

Wanat, Marek & Munzinger, Jérôme, 2012, Biology of the Apionidae (Coleoptera: Curculionoidea) in New Caledonia, a preliminary report, Zootaxa 3554, pp. 59-74 : 63-64

Genus Megatracheloides Lucas, 1920

All six species of this striking New Caledonian genus are associated with various plants of the genus Hibbertia (Dilleniaceae) . They are either oligophagous, utilizing several species of Hibbertia , or monophagous on particular species of this plant genus. Adults feed on leaves, flowers, and buds, gnawing distinct holes. The larvae develop inside fully grown flower buds (one per bud), that fall onto the ground soon after oviposition or larval hatching ( M. cornutus and M. jourdani ), or eventually remained with the inflorescence ( M. bidentipes ). Pupation takes place in a bud, and teneral adults were seen on leaves through October–March. Thus probably two generations can be completed in the flowering season, being extended in most Hibbertia plants. The preferred biotope is maquis, only one species ( M. blaffarti ) is strictly confined to humid forest. More detailed data are summarised below for each species.

Megatracheloides chloris ( Faust, 1889) . Adults of this species, common and widespread in the South, and local in central Grande Terre (only in ultramafic spots, northerly up to Kopeto and Vallée d’Amoa), were mostly collected from Hibbertia pancheri , but occasionally also from the narrow-leaved species like H. lucens and H. trachyphylla . Beetles commonly rest and feed on the underside of leaves ( Fig. 6 ) or pierce flower buds; larval development remains unstudied. Subtle differences in adult morphology were observed between northern, isolated populations ( Wanat 2001; 2008), hence M. chloris may well be a complex of sibling species.

Megatracheloides bidentipes Wanat, 2008 . As in in the previous species, adults were collected from various plants of Hibbertia , and it has been confirmed that this weevil is oligophagous on Hibbertia also in the larval stage. It is the only apionid species regularly collected from, and probably also developing on, H.

trachyphylla (teneral beetles were observed on this plant several times) [5, 6], although the apparently preferred hosts are H. lucens and H. baudouinii . Despite its large body size, it was occasionally collected also from the inconspicuous H. altigena [7], and H. pancheri [8], both of which appear to have flower buds apparently too small to host its larvae. Adults of M. bidentipes were observed feeding on leaves, flowers and flower buds of host plants ( Figs. 7, 8 ). The pupa ( Figs. 9, 10 ) was once found [9] inside a decayed flower bud that was still attached to an inflorescence of H. baudouinii , its contents almost totally consumed by the larva. The adult female emerged in a vial after 16–17 days, a relatively long period for pupal development compared to the European species of Apionidae .

Megatracheloides cornutus Wanat, 2008 and M. jourdani Wanat, 2008 . These two sister species are both apparently monophagous on Hibbertia lucens (occurrence on the closely related H. podocarpifolia requires confirmation). The larvae ( Figs. 11, 12 ) were found inside flower buds lying on shaded ground below the host trees, of M. cornutus on Koghi Mts [10], and of probably M. jourdani at Nyamié creek [11]. At the latter site no adults were found, but the species identity is inferred from the known ranges of these two vicariants in Grande Terre ( Wanat 2008). Unlike smaller larvae of Rhadinocyba species inhabiting neighboring buds, the larvae of both M. cornutus and M. jourdani consume the entire contents of the bud, including rolled petals and stamens, and prepare a kind of pupation chamber with walls made mainly of pressed faeces.

Megatracheloides blaffarti Wanat, 2008 . This is the largest species of the genus, endemic to the Mt Panié range and living there exclusively on Hibbertia comptonii .

Megatracheloides millei Wanat, 2008 . This species is closely related to M. chloris , and at Pic d’Amoa (Powila) was abundantly collected from H. wagapii ( Wanat 2008) . In Aoupinié it is found on the closely related H. pancheri [12]. Distinctness of these two host species of Hibbertia has never been studied in detail.

Figures

FIGURES 1 – 8. 1) The senior author collecting fallen flower buds of Hibbertia lucens infested by the larvae of Rhadinocyba and Megatracheloides; 2, 3) larva of Rhadinocyba singularis (Wencker) inside ovary of H. lucens; 4) mating pair of Rh. singularis at base of opening flower bud of H. lucens, female is piercing a hole towards ovary for oviposition; 5) female of Rh. singularis piercing ovary of H. lucens; 6) Megatracheloides chloris feeding on leaf mid-rib of H. pancheri; 7) female of M. bidentipes feeding on fresh leaves of H. baudouinii; 8) holes in buds of H. baudouinii caused by M. bidentipes. (phot.: 1 — R. Dobosz, 3 — S. Cazeres, rest—MW; sites: 1, 3 – 5 — Nyamié creek, 6 — Poro Plateau, 7, 8 — Upper Rivière Bleue).

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).