Hypseloecus Reuter

Yasunaga, Tomohide, Yamada, Kazutaka & Artchawakom, Taksin, 2015, First Indochinese records of the plant bug genus Hypseloecus Reuter (Hemiptera: Heteroptera: Miridae: Phylinae: Pilophorini), with descriptions of eight new species from Thailand, Zootaxa 3925 (1), pp. 75-93 : 76-77

Genus Hypseloecus Reuter

Hypseloecus Reuter 1891: 50 (n. gen.), type species: Sthenarus visci Puton 1888 , monotypic; Schuh, 1995: 456 (cat.); Kerzhner & Josifov, 1999: 279 (cat.); Yasunaga, 2001a: 310 (diag., note); Yasunaga, 2001b: 147 (diag.); Schuh & Menard, 2011: 369 (diag. redesc.).

Diagnosis. Readily recognized by the following characters: Body rounded or ovoid, tumid, 2.2–3.5 mm in total length, with densely distributed, lanceolate silvery or silky, scale-like setae which are very easily rubbed off (during collecting and/or mounting); head short and broadened, wider than high in frontal view; dorsal body surface weakly shining, usually with dark, simple setae, in addition to scalelike setae; eye small; antenna generally slender and long; bases of mesepisternum and metapleuron often roundly infuscate; hemelytron strongly declivous at cuneal fracture; left paramere thickened; and endosoma usually elongate, C- or J-shaped, often with median appendages. Detailed diagnoses and taxonomic characters are provided by Schuh (1984) as Ambonea Odhiambo (a junior synonym) and Schuh & Menard (2011).

Discussion. This unique pilophorine genus is easily recognized by the above-mentioned characters. The significantly ovoid, thick body shape is unusual within the tribe Pilophorini , in which predominantly ant-mimetic members are accommodated (Schuh, 1989; Yasunaga et al., 2014; Yasunaga & Schuh, 2013). Such a far from antlike body shape of Hypseloecus species may have certain advantages as an adaptation to the unique host preference. Their appearance densely covered with silvery, scale-like setae (which are very easily rubbed off while being collected as in Fig. 2 B vs. C and Fig. 8 C vs. D) on the body surface makes them rather cryptic and harmonious with the habitat, or surfaces of their host plants ( Fig. 2 A). Incidentally, Hypseloecus members at first sight resemble Coridromius species of the subfamily Orthotylinae ; the latter always has very tumid, developed metafemora, however ( Fig. 9 C).

Schuh & Menard (2011) for the first time documented that Hypseloecus species are associated strictly with the hemiparasitic Santalalean host plants, although a single European species, H. visci (Puton) is known to feed on Viscum album L. ( Santalaceae ) ( Schuh, 1995; Wachmann et al., 2004; Wheeler, 2001). In Thailand, H. siamensis was discovered on inflorescence of Scurrula sp. 1 ( Loranthaceae ) growing on Ficus sp. ( Moraceae ) in November ( Fig. 1 A). Many adults and immatures of three species, H. castaneus , H. katrinae and H. sericosagus , were found to co-occur on flowers and fruits of Scurrula sp. 2 heavily parasitizing Homonoia riparia Lour. (Euphorbiaceae) in March ( Fig. 1 B). Flowers of Scurrula sp. 1 and sp. 2 are obviously different from each other although they are yet to be identified.

Adults of Hypseloecus are often attracted to light at night. Collection records suggest that most of the Thai species described below have two or more generations per year. In tropical forests, the hemiparasitic loranthaceous shrubs grow generally very high (near forest canopy), and, therefore, it is usually difficult to collect these mirids in satisfactory numbers as well as to survey their ecology.

The majority of Hypseloecus species have hitherto been known from the Australian and Afrotropical regions (Schuh, 2002–2014). Now the genus is revealed to be widely distributed in the Old World, including continental Asia. There are some more undescribed species in Indonesia and Nepal (Yasunaga, unpublished data), in addition to two known Asian species, H. ifugao ( Schuh, 1984) from the Philippines and H. takahashii Yasunaga, 2001 from the Ryukyus, Japan.

Hypseloecus forms the second most species-rich genus in the tribe Pilophorini , following a typical ant-mimetic genus Pilophorus Hahn which includes more than 120 described species. Pilophorini is assumed to consist of two basic lineages, one oligophagous, non ant-mimetic group and another more or less (sometimes strikingly) antlike and predaceous group ( Yasunaga & Schuh, 2013; Yasunaga et al., 2014). All species of Hypseloecus are now known to be associated strictly with the santalalean host plants. Of the four phytophagous (genus) groups present in Asia ( Sthenaridea Reuter , Parasthenaridea Miller and Lasiolabops Poppius ). Hypseloecus appears to the most speciose.

Recent works based on both morphology and DNA sequence data ( Schuh & Menard, 2011; 2013) improved our knowledge about the phylogenetic position of the Pilophorini . However, Hypseloecus is currently treated as paraphyletic in their analyses involving molecular data (unfortunately lacking any Asian species), although this genus is considered in all likelihood to be a monophyletic group, judging from the morphological characters and information on the biology. There are still quite a few undescribed species in the Oriental Region and subtropical Asia. To demonstrate the more satisfactory classification of Hypseloecus , broader surveys of characters as well as of the Asian faunas are required.

Figures

FIGURE 1. Hosts and habitats of Hypseloecus. A. Sarika near Nangrong Waterfall, Nakhon Nayok Province, Thailand. B. Sarika near Sarika Waterfall.

FIGURE 2. Habitus images of living adult individuals of Hypseloecus species. A. H. siamensis holotype female on Scurrula sp. 1. B. H. castaneus female (SERS). C. H. castaneus male (missing scalelike setae, Nakhon Nayok). D. H. katrinae male (Nakhon Nayok). E. H. nigrobrevis holotype female (SERS).

FIGURE 8. Habitus images of living adult individuals of Hypseloecus species. A. H. phuvasae holotype female (SERS). B. H. sakaerat holotype male (SERS). C. H. schuhianus male (SERS). D. H. schuhianus female (missing scalelike setae, SERS) (Nakhon Nayok).

FIGURE 9. Habitus images of living adult individuals of Hypseloecus species and other related or similar appearing Miridae. A. H. sericosagus holotype male (Nakhon Nayok). B. H. sericosagus female (SERS). C. Coridromius testaceous of the subfamily Orthotylinae (SERS), a sample image for comparison. D. Male of a pilophorine, Aloea nairobi Schuh (at Nairobi National Museum, Kenya), associated only with Aloe monocots in the Ethiopian Region. E. Same, female.