Pilophorus Hahn

Yasunaga, Tomohide & Duwal, Ram Keshari, 2016, Three new species of the ant-mimetic plant bug genus Pilophorus from Japan (Hemiptera: Heteroptera: Miridae: Phylinae: Pilophorini), Zootaxa 4117 (2), pp. 172-182 : 173-175

Genus Pilophorus Hahn

Diagnosis. Recognized by small to moderate size (2−4 mm in total length); usually antlike in overall appearance, elongate (rarely ovoid as in tagoi and miyamotoi discussed below) and always macropterous body form; partly aggregated scalelike setae on scutellum and metepimeron (see Schuh, 1984: 49); presence of anterior band of scalelike setae on corium (a posterior band variable, sometimes interrupted or scattered); often bowed metafemur; fleshy, apically convergent parempodia; usually splayed-out left paramere; ovoid to elongate-oval right paramere; and C- to J-shaped (rarely nearly straight) endosoma often bearing a median spine, flagellum or barb. See Schuh (1984, 1991), Schuh & Schwartz (1988), Yasunaga & Schuh (2013) and Yasunaga et al. (2014) for more detailed diagnostic characters.

Discussion. Pilophorus is composed of morphologically very diverse species. In SE Asia, some members are ‘strikingly’ antlike because of conspicuous modification of the pronotum (cf., P. pleiku ( Schuh, 1984) and P. barbiger Yasunaga & Schuh, 2013 from the Indochina) or the scutellum (cf., P. aurifasciatus Nakatani & Komatsu, 2013 from Malaysia). Most members of Pilophorus are assumed to have strong relationships to certain ant species ( Nakatani et al., 2013; Yasunaga & Schuh, 2013), which presumably produced such myrmecomorphy. In Japan and temperate climate zones of Asia, no species as‘strikingly ant-mimetic’ as those from tropical and subtropical Asia has been discovered yet.

On the other hand, a new species, tagoi , uniquely has a rather ‘conventional’ mirid shape and does not reveal obvious myrmecomorphy as evidenced by its HCR (0.81−0.89). This new species is reminiscent of the eastern Palearctic genus Pherolepis Kulik and we at first wavered between Pilophorus and Pherolepis . Every member of Pherolepis (cf., Figs. 4 C −F, 5C) has the body larger, uniformly dark brown coloration, almost linear antennal segment II, less scalelike setae on the thoracic pleura and abdomen ( Fig. 4 C, E), shiny hemelytron (with scalelike setae restricted or missing in some species), and shortened and broadened right paramere (not much longer than wide), in addition to being associated only with deciduous broadleaf trees unlike the conifers ( Kerzhner, 1988; Yasunaga, 2001; Zhang & Liu, 2009). In temperate and cold temperate climate zones in Japan, two pinaceous conifer inhabitants, Pilophorus miyamotoi Linnavuori and P. varidicornis Kerzhner (see above checklist), are known to have the wide head and ovoid, not much antlike body (HCR> 0.85) ( Fig. 5 A), as seen in Pherolepis . Nonetheless, both species have typical pattern of the scalelike setae (aggregated on the metepimeron). The scalelike setae in tagoi are uniformly distributed not only on the scutellum and hemelytron ( Fig. 1 C, D) but also on the thoracic pleurites and abdomen ( Fig. 4 A), similar to Hypseloecus Reuter ( Fig. 4 G) and Druthmarus Distant ( Fig. 5 E), and the Nearctic Alepidiella Poppius as well; two Old World pilophorine genera Aloea Linnavuori ( Fig. 5 F) and Sthenaridea Reuter ( Fig. 5 D) composed of monocot inhabiting members have the rather scattered and not aggregated scalelike setae on the pleura and abdomen. Although the scalelike setae are not aggregated on the thoracic pleura and abdomen, tagoi has the clavate antennal segment II and brown-matte hemelytron, which are not exhibited by any Pherolepis member but shared by Pilophorus miyamotoi and P. varidicornis .

Comparison with Pilophorus yunganensis Schuh which was described from Fujian (Fukien), China and also has an ovoid, non-antlike body like Pherolepis would merit careful consideration. This species is similar to P. tagoi sp. n. in the general shape and diffused scalelike setae on the widely dull, yellow-brown hemelytron, but is distinct in having the significantly larger body, partly shiny fuscous hemelytron and totally different shape of the male genitalia ( Schuh, 1984). Currently, we conclude that P. t a go i is better to be placed in Pilophorus rather than Pherolepis , based on the following characters: Clavate antennal segment II; scalelike setae somewhat forming patches anterolaterally and apically on scutellum; wholly brown-matte, not shiny hemelytron, with appressed, scalelike setae weakly aggregated partly on corium and base of cuneus; and right paramere elongate, not significantly shortened. No species in Pherolepis nor any pilophorine genus discussed above is known to be associated with conifers, which may further support the placement of tagoi in Pilophorus .

The Japanese fauna of Pilophorus has been known by 10 members thus far; one of these (misidentified as P. formosanus Poppius ) is now confirmed to represent an undescribed species (see below, P. nakatanii ). The present work reveals at least 12 species occur in Japan. Of these, P. erraticus Josifov, P. l u c i d us Linnavuori, P. pseudoperplexus Josifov and P. setulosus Horváth , are associated with deciduous broad-leaved trees; P. miyamotoi Linnavuori , P. nakatanii sp. n., P. tagoi sp. n., and P. varidicornis Kerzhner are restricted to conifers; and P. okamotoi Miyamoto & Lee and P. t y p i c us (Distant) are found from various herbs or shrubs. Although host associations of two Japanese species, P. niger Poppius and P. maeharai sp. n., remain unclear, a few adults of the former were observed to have preyed on a coccid on bark of Cinnamomum tenuifolium (Makino) Sugim. ex H.Hara (Lauraceae) ( Yasunaga, 2001), and those of the latter was found moving quickly on bark of Prunus jamasakura Sieb. ex Koidz. (Rosaceae) .

Pilophorine host plant associations are presumed to be influenced by the presence of acceptable prey organisms ( Schuh & Schwartz, 1988). Some members, such as P. setulosus and P. typicus ( Fig. 5 B), are found on a variety of plant taxa. We assume such species may be predominantly predaceous, as evidenced by a series of observations on P. typicus , now considered to be a potential candidate for biological control programs against economically important pests ( Ito et al., 2009: 2011). However, the Japanese population of P. typicus is assumed to comprise two sibling species based on two genotypes detected by DNA sequence data; these different races currently cannot be determined morphologically ( Ito et al., 2011). Therefore, a broader survey on characters, including closer examination of the genitalia, is required for this widespread pilophorine.

Figures

FIGURE 1. Habitus images of new Japanese Pilophorus spp. A. P. nakatanii, holotype male (AMNH _ PBI 00380410). B. Same, dry-preserved condition, right lateral view. C. P. tagoi, male. D. Same, female. E. P. maeharai, holotype male (00380411). F. Same, ventral view. G. Same, female.

FIGURE 4. Left lateral side of body (A, C, E, G) and frontal head (B, D, F, H) of Asian pilophorines. A − B. Pilophorus tagoi n. sp., paratype. C − D. Pherolepis fasciatus (Kerzhner) from Hokkaido, Japan. E − F. Pherolepis kiritshenkoi (Kerzhner) from Honshu, Japan. G − H. Hypseloecus katrinae Yasunaga, Yamada & Artchawakom from Nakhon Nayok, Thailand.

FIGURE 5. Old World pilophorines, habitus images of live individuals. A. Pilophorus miyamotoi Linnavuori from Honshu, Japan. B. P. typicus (Distant) from Kyushu, Japan. C. Pherolepis fasciatus (Kerzhner) from Hokkaido, Japan. D. Sthenaridea piceonigra (Motshulsky) from Yangon, Myanmar. E. Druthmalus sp. from Chitwan, Nepal. F. Aloea nairobi Schuh from Nairobi, Kenya.