Neolygus Knight 1917
Creators: name: Yasunaga, Tomohide
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hemiptera
Miridae
Neolygus

description: Genus Neolygus Knight, 1917
Diagnosis: Neolygus is distinguished from other superficially similar genus groups (e.g. Anthophilolygus Yasunaga, Schwartz & Chérot, 2018, Apolygus China, 1941, Miyamotolygus Yasunaga, Schwartz & Chérot, Prolygus Carvalho, Taylorilygus Leston, 1952) by the following combination of characters: body moderate in size (4–7 mm), oval to elongate oval; basic coloration mostly pale green (e.g. Figs. 1A–G, I, J, 3; some species with reddish or fuscous general coloration as in Fig. 1H) but easily fading to pale brown in dry-preserved specimens (Fig. 4A–C, GI); dorsal surface shining, finely punctate, with uniformly distributed, pale, simple setae; vertex always with a continuous basal transverse carina (Fig. 16B); cuneus unicolorous and its apex not darkened; tibial spines pale brown or reddish brown, without dark spots at bases; parameres (cf. Figs. 6A–D, G–J, 7A–B, E, 10, 12A–B, D ¬–E, 18E–F, 19G–H, 20K–N) with distinct sensory setae; left paramere L-shaped, with apical portion of sensory lobe more or less protuberant and hypophysis usually thickened apically; right paramere bird-head-shaped apically, with stout sensory lobe and developed, claw-like hypophysis; phallotheca expanded apically, usually with a small process (cf. Figs. 14A–G); vesica principally with spiculum (SP), ventral sclerite (VS), median sclerite (MS) and basal sclerite (BS) (cf. Figs. 6E, K–L, 7C–D, F, 8C ¬–D, 9A–D, 11C, H, 12C, 14D); female genital chamber usually toughened with sclerites (SDS) (cf. Fig. 12F–G), similar to those found in members of the genus Philostephanus Distant, 1904 or its allies (Yasunaga & Schwartz 2007; Yasunaga 2016); sclerotized rings thick-rimmed, sometimes enlarged and contiguous to each other mesially (cf. Fig. 8G); dorsal labiate plate usually with large dorsal sac (cf. Fig. 16K) and strongly spinulate, posterior directed pair of sclerites on ventral surface (PPD) (Fig. 12G); posterior wall without dorsal structure; with widened lateral lobes, sometimes fused together or overlapped mesially (cf. Figs. 14B, E, H); interramal lobes semi-circular (cf. Figs. 17B–C) or squared (cf. Figs. 19K, 20D); lateral lobes with uniformly distributed wide plate-like spinules (cf. Fig. 18K); interramal lobes with predominately laterally distributed narrow sharply pointed spinules (cf. Figs. 14C, F, I); interramal sclerite with faint median process (Fig. 11K).
Distribution. Holarctic and Oriental regions.
Discussion. In the Oriental Region and Asian warm temperate zones, genuine Neolygus members are not abundant, but a number of species belonging to Miyamotolygus, Prolygus or other genera instead of Neolygus predominate (Yasunaga et al. 2018a). The species of other genera frequently have parameres of similar shape; however, each group is distinct in the pattern of vesical sclerites and female genitalic structures (cf. Yasunaga et al. 2018a). Neolygus species are considered cryophilic, and those inhabiting the Oriental Region are obviously restricted to cool highland zones generally grown with deciduous broadleaf vegetation (cf. Zheng et al. 2004; Yasunaga et al. 2012). Emergence of three Neolygus species known from the subtropical Ryukyus of southwestern Japan (the northernmost Oriental subtropics without highland area), N. kyushuensis (Yasunaga, 1991) (Fig. 2A), N. tokaraensis (Yasunaga 1991) (Fig. 2A) and N. yonanus n. sp. (see below description), is apparently limited to spring; these species diapause in the egg stage for more than 10 months.
The phylogenetic position of Neolygus within the tribe Mirini has yet to be clearly posited. It was regarded as a subgenus of Lygocoris Reuter, 1875, but a plausible relationship between Neolygus and Lygocoris remains in doubt as homologous hypotheses for structures of the male and female genitalia are not yet realized (Yasunaga 1991a, 2023; Yasunaga & Vinokurov 1999). The female genitalia of Neolygus species have been insufficiently employed for the classification. During the present examination, more than 20 Neolygus congeners were observed (e.g. Figs. 8E–H, 12F–G, 14E–F, 16J–O). Several species have more or less asymmetrical genital chamber with partly sclerotized dorsal sac (e.g. Fig. 14F) that is sometimes strongly protruded posteriorly and fused with anterior part of the posterior wall (e.g. Fig. 16K). Similar structures are reported in the East Asian genus Philostephanus Distant, 1904 and its allies (Yasunaga & Schwartz 2007; Yasunaga 2016), to which Neolygus may be related. Nonetheless, further critical analysis is required to document a significant portion of the Oriental Mirini and reliable elucidate their phylogenetic relationships.
Owning to lack of information on the female genitalia, it is currently difficult (or often impossible) to make exact identification of the Neolygus species by female specimens alone. As mentioned in my previous work (Yasunaga 2023), a large number of the described species are known only by the males, and numerous undetermined female specimens are remaining in public and personal collections. In addition, some species equally have uniformly pale green, immaculate body (Figs. 3A–B, 4G–H), whereas others have remarkable color variation (Fig. 3C–F). Reliable species identification is depend upon examination of the male genitalia for the time being, although the females of several congeners, with unique genitalic structures, can be correctly determined (e.g. Figs. 8G–H, 12F, 16M–O). Continuing attempt to match up conspecific male and female is essential.
The majority of Neolygus species are univoltine and propagate on broadleaf shrubs or trees, particularly the flower buds or inflorescences (e.g., Yasunaga 2021; Noguchi et al. 2023). The eggs, oviposited into shoots, usually hibernate. Only a few species are known to inhabit conifers (Kelton 1980; Yasunaga 2001). Several species are known as agricultural pests of economic importance injurious to fruit products or medicinal plants (Knight 1927; Kelton 1982; Wheeler 2001; Yasunaga et al. 2018b; Yasunaga 2021). Miyazaki et al. (2019) observed that a female adult of Neolygus kyushuensis (Yasunaga) could survive for 32 days, reared with a synthetic diet composed of fermented milk beverage and dried larvae of chironomid midges (both commercially available). The methodology was also applied to rearing several 4th to 5th instar immature forms (N. esakii and N. zhugei), which successfully developed into the adult stage (Noguchi et al. 2023; Yasunaga unpublished observation). These results imply that Neolygus members partially have zoophytophagous food habit.
Examination of pertinent Neolygus specimens revealed that N. tsugaruensis (Yasunaga, 1992) [originally described as Lygocoris (Neolygus) tsugaruensis Yasunaga, 1992: 522] is a pale-colored variant of N. roseus (Yasunaga, 1991) (Figs. 1H, 19L–O). Accordingly, Neolygus tsugaruensis (Yasunaga, 1992) syn. n. is herein proposed as a junior synonym of Neolygus roseus (Yasunaga, 1991).
description: Published as part of Yasunaga, Tomohide, 2024, New species of the plant bug genus Neolygus Knight from Japan, Taiwan and Thailand (Hemiptera: Heteroptera: Miridae: Mirini), pp. 451-487 in Zootaxa 5446 (4) on pages 452-453, DOI: 10.11646/zootaxa.5446.4.1, http://zenodo.org/record/11102124