Alyculus Kazantsev, 1999

Ata, Va C L Av Pa L & K, L A D I S L Av B O C A, 2012, Revision of the genus Alyculus Kazantsev, 1999 (Coleoptera: Lycidae), Zootaxa 3564, pp. 61-67 : 62-63

Alyculus Kazantsev, 1999

Alyculus Kazantsev, 1999: 252 .

Type species: Alyculus kurbatovi Kazantsev, 1999 (by monotypy).

Diagnosis. Alyculus is the only net-winged beetle with shortened elytra ( Figs 1–2 ). Additionally, the very small body (1.1–2.7 mm) and shape of male genitalia ( Figs 9–12 ) distinguish the genus from other lycids.

Redescription. Male. Body tiny, dark testaceous or brownish black, never brightly colored ( Figs 1–2 ). Head small, hypognathous, cranium with prominent frontal part, antennae inserted on frontal tubercles, cranium sometimes with apparent cell-like structure, covered with sparse long pubescence ( Fig. 5 ). Eyes large, hemispherically prominent, eye diameter slightly larger than interocular distance. Antennae slender to moderately robust, filiform or antennomere 3 and subsequent ones slightly compressed; antennomere 1 long, antennomere 2 very small, approximately as long as wide, antennomere 3 slender, parallel-sided ( Fig. 7 ) or sometimes compressed, wide ( Fig. 6 ), subsequent antennomeres becoming gradually more slender and parallel-sided ( Figs 6–8 ). Mouthparts tiny, reduced, with very small, vestigial mandibles, labrum minute, maxillary palpi 4-segmented, both palpi with apical palpomeres pointed at apex. Pronotum strongly transverse, widest at basal margin, with posterior angles acutely prominent, lateral and basal margins variable in shape; pronotum either without any keels or costae, or longitudinal keel present along midline ( Figs 3–5 ); disc with punctures and sparse, long, erected pubescence. Scutellum bilobed apically, distal processes slender, projected obliquely backwards ( Fig. 5 ). Elytra without costae or reticulate cells, shortened, tapering to apex, rounded apically, densely covered with minute papillae bearing setae, which form dense pubescence ( Fig. 1 ). Wings long, without veins, lightly infuscate. Legs slender, tarsomeres similar in width, slender. Male genitalia trilobate, phallus slender, usually slightly shorter than parameres, parameres widest at basal two fifths to one fourth, connected dorsally, approaching each other ventrally, phallobase simple ( Figs 9–12 ). Body length: 1.1–2.7 mm.

Remark. Only Lyropaeus and Platerodrilus have been collected in females and their neoteny documented ( Bocak & Matsuda 2003). Females of the remaining Lyropaeinae genera, including Alyculus , are unknown. Although a limited number of Alyculus specimens are known, and therefore the female neoteny cannot be inferred from the absence of females in the available material, the neotenic development is hypothesized on the basis of male morphology and molecular data, which place the genus in relationships with Lyropaeus Waterhouse, 1878 and other neotenic lineages (Bocak et al. 2008, Bocak & Bocakova 2008).

Distribution. Alyculus is at present known from the Sunda Shelf Islands, but without any record from the Malay Peninsula, whose fauna is zoogeographically very close to Sumatra and Borneo ( Bocak & Yagi 2010). Three species occur in the mountain chain spreading from Northern Sumatra ( A. wittmeri reported from the Aceh Province) through the central part of the island ( A. tujuhensis sp. nov., Barisan Mts) to Western Java ( A. kurbatovi from Mt. Gede and environs). The later mountain region was repeatedly connected with Sumatra by the subaerial Sunda Strait ( Voris 2000) and shares fauna with Southern Sumatra. Although Sumatra in the present form has fairly recent origin, the presence of a limited extent of dry land during the time when most of Sumatra was submerged (~25–15 mya, Hall 2002) was supported by the dated evolution of another neotenic lineage, Scarelus Waterhouse, 1879 ( Malohlava & Bocak 2010) . The highly morphologically diversified species of Alyculus in Sumatra and Java also support the continuous presence of some dry land, as the neotenic lineages do not disperse and occupy for a long time very restricted ranges ( Bocak & Malohlava 2010). A single species is known from Borneo, which is a much older island and rain forests were preserved in the region during the drier Pliocene and Pleistocene periods to a large extent (Canon et al. 2009). Therefore, Alyculus may be widespread also in the Crocker Range and the Kinabalu Massif.

Biology. These lycids were sifted ( A. kurbatovi ), intercepted by Malaise traps ( A. barclayi sp. nov., A. wittmeri ) or swept from lower vegetation under the rain forest canopy ( A. tujuhensis sp. nov., A. kurbatovi ). All species of Alyculus are generally rare and individual species are known in a single or a few specimens from very limited ranges, typically represented by mountain tops. These small-bodied and feebly sclerotized neotenic lycids show a tendency to remain in humid conditions at the lowest herb stratum under canopy and they seldom fly. Although a low number of specimens have been collected, we can say that these neotenic lycids fly close to the surface of soil (typical height of flight up to 20 cm) and have never been collected in higher strata of vegetation. Their flight is very slow and the flying activity is restricted to weather conditions without wind, at high temperatures and humidity. Probably, the flight of males serves only for finding a conspecific female as low dispersal ability of males must be expected as a consequence of feeble, small body, flightlessness of larviform females, rareness and the dependence on stable rainforest habitats. The extensive distribution and vicariant ranges of Alyculus resemble the distribution of neotenic net-winged beetle Scarelus ( Malohlava & Bocak 2010) and the species ranges correspond with the uninterrupted presence of the South East Asian rain forests in the mountains of Sumatra, western Java, and Northwestern Borneo during drier periods of the Pleistocene ( Voris 2000). All recently collected species of Lyropaeinae inhabit undisturbed humid forests ( Bocakova 2006) and are seldom collected in ecosystems affected by human activities. Considering their dependence on the original habitats and presumed low dispersal propensity, these animals are deeply threatened by the undergoing deforestation in the region ( Sodhi et al. 2004).

Figures

FIGURES 1 – 8. General appearance: 1. Alyculus wittmeri Bocakova; 2. A. barclayi sp. nov. Pronotum: 3. A. wittmeri Bocakova; 4. A. tujuhensis sp. nov. Head, pronotum, and scutellum: 5. A. kurbatovi Kazantsev. Basal antennomeres: 6. A. barclayi sp. nov.; 7. A. tujuhensis sp. nov.; 8. A. kurbatovi Kazantsev. Scales 0.5 mm (Figs 1 – 2), 0.1 mm (Figs 3 – 8).

FIGURES 9 – 12. Male genitalia: 9. A. kurbatovi Kazantsev (redrawn from Kazantsev 1999, Fig. 4); 10. A. tujuhensis sp. nov. 11. A. barclayi sp. nov.; 12. A. wittmeri Bocakova. Scales 0.1 mm.