Metanoeus Waterhouse, 1879

Weiszenstein, Martin & Bocak, Ladislav, 2011, A Review Of The Genus Metanoeus From The Philippines (Coleoptera: Lycidae), Raffles Bulletin of Zoology 59 (2), pp. 163-170 : 164-165

Metanoeus Waterhouse, 1879

Metanoeus Waterhouse, 1879: 73 .

Type species. – Lycus (gen. 37) conformis Waterhouse, 1878: 115; Bourgeois, 1891: 347 (by subsequent designation).

Differential diagnosis. – Metanoeus is defined mainly by the presence of the unique very obtuse pronotal carinae (Fig. 2), extremely long lamellae of male antennae (Fig. 3), and vestigial valvifers in the ovipositor. The genus resembles the related Cautires Waterhouse, 1879 in the presence of nine longitudinal costae on each elytron, but these genera differ in the structure of the pronotal carinae and especially in the structure of male genitalia. Unlike the very diverse shape of the phallus in Metanoeus (Figs. 5–16), Cautires have, as a rule, a very slender, simple phallus with only two small thorns in the internal sac ( Bocak, 2002). Another very species-rich metriorrhynchine genus, Xylobanus Waterhouse, 1879 , differs in four longitudinal costae on each elytron. The last Oriental genus Bulenides Waterhouse, 1879 was recently synonymized with Cautires ( Dudkova & Bocak, 2010) . The given characters enable reliable identification of both sexes in the Oriental region. Similar obtuse carinae were found in some Metriorrhynchus Gemminger & Gemminger et Harold, 1869 , which differs in the larger body, long slender phallus, only slightly shortened valvifers, and serrate male antennae or much shorter lamellae in some Papuan species ( Bocak, 2007). Some characters reported for Metanoeus , such as the sclerotization of the vagina, long processes of scutellum and long, basally attached male antennal lamellae, remind of some Papuan representatives of Metriorrhynchini , but none of these occurs sympatrically with Metanoeus .

Redescription. – Body small to medium sized, 6–18 mm, weakly sclerotized, dorso-ventrally flattened (Fig. 1). Colouration variable, most species uniformly yellow dorsally in the Philippines, variably coloured in the Great Sunda Islands and continental Asia. Head small, partly hidden by pronotum, without rostrum, with large eyes in both sexes. Male antennal lamellae long, attached to bases of antennomeres, slender basally, female antennae serrate (Fig. 4). Maxillary palpi 4-segmented, slender, apical palpomere parallel-sided, labial palpi 3-segmented, similar in shape. Pronotum with seven areolae, carinae obtuse (Fig. 2). Scutellum deeply emarginate at apex. Elytra parallel-sided to slightly widened backward, each with nine longitudinal costae, four of them stronger, intermediate costae weak. Male genitalia with phallus and phallobase, parameres absent. Phallobase small, phallobasal membrane extensive, at least partly sclerotized. Phallus variable in shape, often considerably shortened (Figs. 5–16). Internal sac with three pairs of thorns or only partly sclerotized membranous structures. Female genitalia short, with plate-shaped coxites and short valvifers modified into small plates; vagina often considerably sclerotized; spermaduct usually extremely long, in species with membranous vagina shorter ( Bocak, 2002).

Diversity, distribution and conservation. – There have been described only 23 species of Metanoeus ( Kleine, 1933) . All species were reported from the tropical rain forests in the Great Sundas, Peninsular Malaysia, Indochina and the Philippines and no record is available outside these regions. The highest diversity of Metanoeus was reported from northeastern Borneo and Sumatra. Concerning the distribution and diversity of Metanoeus throughout its range, we may consider the Philippine Metanoeus fauna to be a result of dispersal from the Sundaland. The Huxley‘s line separating the Philippines and the Oriental region represents a valid zoogeographical border for several lycid genera such as Cautiromimus Kleine, 1926 or species groups of Metriorrhynchus and many other animals (Brown & Guttman, 2002), but some genera, such as Metanoeus or Cautires , are known from the Philippines and do not occur beyond the Wallace line in Sulawesi and further to the East ( Bocak, 2002).

The lower montane forests habitats typical for Metanoeus lie in the most densely populated regions of Java, Sumatra, and the Philippines and are highly endangered by deforestation. Especially, the fauna of the Philippines may be strongly damaged by the ongoing loss of habitats. The results show, that many previously described taxa were typologically defined on the basis of a few specimens and they represent in fact complexes of highly similar and often distantly related species occurring in small ranges. The extraordinary biodiversity of the Philippines is known also in other groups of animals and the archipelago is considered as one of the biodiversity hotspots ( Myers et al., 2000). Further deforestation may quickly lead to substantial loss of the diversity ( Sodhi et al., 2004).

Biology. – Metanoeus occurs from lowlands to montane forests and larvae live in decaying moist wood in the final stage of decomposition. The larva of one Bornean species was described by Bocak & Matsuda (2003). The recent observation showed similar biology also in Plateros Bourgeois, 1879 , Cautires , and Xylobanus (Levkanicova & Bocak, 2009) . Most adults of the Philippine species were collected by general sweeping of lower undergrowth of the tropical rain forest where they slowly move or sit on leaves. Although males of some species have extraordinary large eyes, which usually indicates a nocturnal activity, Metanoeus are only seldom collected at light. The bright coloration of adults is regularly shared with unrelated syntopically occurring species from various lycid genera and may have a warning function as all lycids are unprofitable to predators due to the content of bitter and smelling compounds ( Eisner et al., 2008; Bocak & Yagi, 2010).

Figs. 1–12. 1: Metanoeus sp. , female, general appearance; 2: Metanoeus sp. pronotum; 3: Metanoeus sp. , male, basal antennomeres; 4: Metanoeus sp. , female, basal antennomeres; Male genitalia: 5–7: Metanoeus parallelus , new species, 8: M. salvani , new species, 9–10: M. ellipticus , new species, 11–12: M. matsudai , new species. Scale 1 mm.