Type material. Lectotype: RUSSIA • ♂; Primorsky Terr.: Lesozavodsk [Ussuri], 45.46666°N, 133.41666°E, no date provided, V. Jakovlev coll., (ZISP_ENT 00016235) – Paralectotypes: RUSSIA • 2♂♂; Primorsky Terr.— Other material. RUSSIA, Khabarovsk Terr., Primorsky Terr. • many ♂♂, ♀♀ (see File S1).

Length in male 5.1–5.6 mm, in female 5.4–5.8 mm. Head mostly yellow; clypeus mostly dark brown (Fig. 15A); antennal segment I yellow, sometimes with red tinge, antennal segment II yellow with apical 1/2–1/3 brown to dark brown; pronotum mostly yellow, sometimes posterior part brown to dark brown or pronotum mostly brown to dark brown with yellow marking anteriorly; scutellum mostly yellow, brown to dark brown basally; clavus mostly brown to dark brown, rarely mostly yellow with brown to dark brown markings; corium yellow, brown to dark brown anteriorly and posteriorly, sometimes mostly brown to dark brown; lateral margin of embolium dark brown; cuneus yellow, brown to dark brown basally and apically (Fig. 10A, B); pleura varying from mostly whitish yellow with brown markings to mostly brown to dark brown; metathoracic gland evaporative area whitish yellow; coxae whitish yellow to yellow; femora yellow with apical half red or femora entirely red, brown rings on apical part of femora absent or faint, rarely distinct; tibia with dark brown to black marking at base of spines, pale brown to brown marking at base of tibia present. — Male genitalia. Apical process of left paramere shorter than paramere body (Fig. 19A, B); median and lateral sclerites of vesica present; wing-shaped sclerite elongate, ca 3–4× as long as wide, with lateral margin straight, subequal to 1/3 of ventral sclerite, wider than ventral and median sclerites; sublateral sclerite present, pointed apically, twice as long as wide; needle-shaped sclerite very short, placed at base of vesica (Fig. 16A, B).

Apolygus adustus is known from the Russian Far East: Amur Province – not confirmed, see Notes (Kulik 1965a), Khabarovsk Territory (Kulik 1965a; Kerzhner 1988b; Dubatolov et al. 2023; ZIN), Primorsky Territory (Jakovlev 1876; Lindberg 1934; Kulik 1965a; Kerzhner 1988b; Miyamoto et al. 1994; ZIN), Sakhalin Island – not confirmed, see Notes (Miyamoto et al. 1994). It was also recorded from Korea (Oh et al. 2018).

Apolygus adustus lives on broadleaf trees and bushes (Kulik 1965a). Kulik (1974) reported it from Maackia amurensis Rupr. (Fabaceae).

Oh et al. (2023) mentioned that A. adustus is known from Japan, but Yasunaga (2023) did not include it to the checklist of the Japanese species, therefore, it is likely that A. adustus does not inhabit this country. Judging from the images and drawings of the genitalia structures and habitus (Josifov and Kerzhner 1972; Oh et al. 2018), the specimens from Korea are conspecific with those that are preserved at ZIN. In Russia this species was previously recorded from Amur Province, Khabarovsk and Primorskiy Territories and the south of Sakhalin Island (Kulik 1965a; Miyamoto et al. 1994; Kerzhner 1988b; Dubatolov et al. 2023). Here we confirm that A. adustus is distributed in Primorsky and Khabarovsk Territories, but we did not have the specimens from the Amur Territory and Sakhalin Island. Among species known from the Far East, A. adustus is most similar to A. fraxinicola in coloration (Figs 10A–D), but the latter differs in the cuneus often with red tinge along its inner margin or mostly dark brown to black (Fig. 10C, D), its hind femur often has the distinct brown or red bands apically, and the vesica has the long needle-shaped sclerite (Fig. 16E).

Among the Japanese species, A. adustus is similar to A. amamicus Yasunaga, 2023 in the coloration and size (Yasunaga 2023). This species is known from females only. However, Yasunaga (2023) did not compare the new species with A. adustus, and further studies of male genitalia and molecular data are needed to confirm the status of A. amamicus.

Type material: Holotype: RUSSIA • 1♂; Primorsky Terr.: Kedrovaya Pad’ Nature Reserve, 43.067°N, 131.617°E, 29 Jun 1982, I. M. Kerzhner, Fraxinus rhynchophylla Hance (Oleaceae), (ZISP_ENT 00016585) – Paratypes: RUSSIA • 9♂♂, 13♀♀; Primorsky Terr. — Other material. RUSSIA, Khabarovsk Terr., Primorsky Terr. • 4♂♂, ♀ (See File S1).

Length in male 5.2–5.5 mm, in female 4.9–5.6 mm. Head color varying from mostly yellow to pale brown with red tinge, rarely mostly brown to dark brown; clypeus often mostly dark brown to black or only dark brown to black apically (Fig. 15B); antennal segment I yellow to pale brown, sometimes with red tinge; antennal segment II mostly yellow, with brown to dark brown apical 1/4–1/5; pronotum usually yellow, rarely mostly brown to dark brown; scutellum usually brown to dark brown with yellow to pale brown apex, sometimes mostly yellow to pale brown with brown to dark brown base; clavus mostly brown to dark brown; corium yellow, usually brown apically and posteriorly, sometimes mostly brown to dark brown; lateral margin of embolium dark brown; cuneus yellow, often with red tinge, brown basally and apically, sometimes entirely brown (Fig. 10C, D); pleura brown, sometimes with yellow markings, metathoracic scent gland evaporative area yellow, sometimes red or brown; coxae whitish yellow, femora often yellow with red markings at least apically, sometimes mostly red or red brown; hind femora with brown to dark brown bands; tibia with dark brown to black markings at base of spines, bases of tibiae with red, brown to dark brown marking, sometimes this marking very pale. — Male genitalia. Apical process or right paramere shorter than paramere body (Fig. 19C, D); wing-shaped sclerite elongate, ca. 4× as long as wide with straight margin, subequal to half of ventral sclerite, wider than lateral and median sclerites; sublateral sclerite present, toothed, elongate and acute; needle-shaped sclerite present, exceeding apex of wing-shaped sclerite, but not reaching apex of ventral sclerite (Fig. 16E, F).

Apolygus fraxinicola is known from the Russian Far East: Primorsky Territory (Kerzhner 1988a, 1988b; ZIN), Kuril Islands – not confirmed, see Notes (Kerzhner 1988a, 1988b; Kerzhner and Marusik 1997; Kerzhner et al. 2004; Kanyukova and Marusik 2006), Khabarovsk Territory (ZIN). It was also recorded from Korea (Kim and Jung 2018b; Oh et al. 2018) and Japan (Yasunaga 1992a, 2023).

Specimens were collected from Fraxinus rhynchophylla and Fraxinus mandshurika (Kerzhner 1988a, 1988b), Syringa reticulata (Yasunaga 1992a), Syringa amurensis (ZIN) (Oleaceae).

Kerzhner (1988a) recorded this species from Kunashir Island based on the single series from Dubovoe (Kunashir Is). We examined these specimens and found that there was only a single teneral male with very pale aedeagus. Therefore, their identification could not be confirmed. Apolygus fraxinicola was also listed by Kerzhner and Marusik (1997), Kerzhner et al. (2004), Kanyukova and Marusik (2006) from Kunashir Island, but it is unclear whether they referred to the works of Kerzhner (1988a) or recollected some specimens later. The drawing of vesica provided by Yasunaga (1992a) corresponds to that from the Russian Far East. We report this species from the Khabarovsk Territory for the first time. Among the species from the Russian Far East, A. fraxinicola is most similar to A. adustus, but the latter differs in the cuneus without red tinge (Fig. 10C, D) and very short needle-shaped sclerite (Fig. 16E). Among the Japanese species, A. fraxinicola is most similar to Apolygus horologiatus Yasunaga, 2023 externally, but the latter differs in the presence of two needle-shaped sclerites (Yasunaga 2023).

Type material. Holotype: RUSSIA • 1♂; Sakhalin Prov.: Tobuti, Siretoko Peninusla, Sakhalin Is., 46.5°N, 143.3°E, 04 Aug 1947, Dyakonov, (ZISP_ENT 00016303) – Paratypes: RUSSIA • 3♂, 3♀; Sakhalin Prov. — Other material. JAPAN, RUSSIA, Primorsky Terr. • many ♂♂, ♀♀ (See File S1).

Length in male 4.7–6.2 mm, in female 4.8–5.5 mm. Body brown to dark brown, head yellow to pale brown with dark brown to black markings, sometimes mostly dark brown to black; clypeus dark brown to black (Fig. 15C); antennal segment I mostly yellow to pale brown, often with brown to dark brown stripe ventrally; antennal segment II mostly dark brown, rarely with yellow to pale brown band in the basal half; pronotum, scutellum and hemelytron often uniformly dark brown to black, sometimes pronotum and scutellum at least partly pale brown and cuneus sometimes pale brown medially, rarely corium mostly yellow with brown to dark brown marking posteriorly (Fig. 10E, F); lateral margin of embolium brown to dark brown; pleura dark brown to black, sometimes with yellow markings, rarely yellow with brown markings; metathoracic gland evaporative area yellow; legs yellow, at least hind femur with red tinge and brown or red bands apically; bases of middle and hind femora brown; tibiae with markings at bases of spines. — Male genitalia. Apical process of right paramere as long as paramere body (Fig. 19E–H); wing-shaped sclerite elongate, ca. 5–7× as long as wide with straight margin, 0.75× as long as ventral sclerite, its outer margin straight, narrower than lateral sclerite and wider than median sclerite; sublateral sclerite present, toothed, triangular with acute angle; needle-shaped sclerite present, extending beyond secondary gonopore and not reaching apex of wing-shaped sclerite.

Apolygus furvus inhabits Russian Far East: Amur Province – not confirmed, see Notes (Kerzhner 1972; Kulik 1974), Primorskiy Territory (ZIN), Sakhalin Island (Kerzhner 1972; Kulik 1974; Kerzhner 1977, 1978, 1988b; Kanyukova and Kerzhner 2010; ZIN), Kuril Islands (Kerzhner 1972; Kuik 1974; Kerzhner 1977, 1978, 1988b; Kerzhner and Marusik 1997; Kerzhner et al. 2004; Kanyukova and Marusik 2006; ZIN). Records from Khabarovsk and Primorskiy Territories (Kerzhner 1972; Kulik 1974) refer to A. infamis (see Notes). This species was also recorded from Japan (Yasunaga 1992a, 2023; ZIN).

Apolygus furvus was collected from Hydrangea paniculata (Hydrangeaceae) (Kerzhner 1977, 1978, 1988b). Yasunaga (1992a) also recorded this species from Polygonum cuspidatum (Polygonaceae), Actinidia polygama (Actinidiaceae), Ligustrum obtisifolium (Oleaceae). At least some of those records can refer to A. infamis or A. shikotansp. nov. (see Notes).

Kerzhner (1972) described A. furvus from the different regions of the Russian Far East (Primorskiy, Amur and Khabarovsk Territories, Sakhalin Island, Kuril Islands). He provided drawings of the vesica and parameres, however, these genital structures belonged to another species, A. infamis, which was described later from the paratypes of A. furvus (Kerzhner 1977) (see diagnosis for A. infamis). We examined the holotype of A. furvus including genitalia (Tobuty, Siretoko Peninsula, Sakhalin), and found that the specimen is teneral, and its sclerites are underdeveloped. For example, the median sclerite which is present in all species of Apolygus, is indistinct in this specimen (Fig. 16G, H). Additionally, we could not see the needle-shaped sclerite. It is unclear whether it is absent or soft and membranous. We dissected all other males of the specimens identified as A. furvus and found that all of them have distinct median and needle-shaped sclerites. Although there is a possibility that the holotype and paratypes belong to the different species, we consider them as conspecific. There were three specimens from the Primorskiy Territory originally assigned to this species by Kerzhner (1972). Two of them from Vinogradovka and Gorno-Taezhnaya Station are females, and their identification cannot be confirmed. The third specimen from Suchan now is a holotype for Apolygus infamis (Kerzhner 1977). However, we confirm that A. furvus lives in the Primorskiy Territory based on the specimens collected later and preserved at ZIN. The single specimen from Khabarovsk Territory originally assigned to A. furvus was also transferred to A. infamis. Apolygus furvus was recorded from a single location in Amur Province (Korsakovo). However, only females belong to this series, and we could not confirm the identification of those specimens. Kerzhner (1977) synonymised A. furvus with A. hilaris, however, later the same author treated those two species as separate (Kerzhner 1988b). According to the original description (Horváth 1905), A. hilaris is reddish yellow, and the posterior part of corium has black marking. This fits the description of the specimens currently assigned to A. hilaris, and A. furvus has brown to black corium.

In Yasunaga (2023) the vesica of paratype was depicted and it has needle-shaped sclerite shorter than the wing-shaped sclerite as in the specimens examined by us. However, in Yasunaga (1992a) the needle-shaped sclerite is longer than the wing-shaped sclerite, and those specimens can belong to another species. Among the voucher specimens used for the phylogenetic analyses, there is a specimen M199, which is similar to A. furvus in coloration, and its right paramere has a long apical process. However, it has two short needle-shaped sclerites at base, and might represent a new species (Fig. 16C, D).

Among the species known from the Russian Far East, A. furvus is most similar to A. infamis and A. shikotansp. nov. These two species differ from A. furvus in the concave outer margin of wing-shaped sclerite (Figs 17F, 17G, 18C, 18D). Apolygus infamis also differs in the shorter wing-shaped sclerite, which is 4× as long as wide, and A. shikotansp. nov. differs in the apical process of its right paramere shorter than the paramere body (Fig. 19W). Among other dark brown to black species of Apolygus, A. ater, A. furvellus, A. miyamotoanus, and A. nigricans have the needle-shaped sclerite longer than the wing-shaped sclerite, and A. ater also differs in having the dark brown femora. In A. atrobellus, A. miyamotoanus, A. nigricans and A. seonheulensis the apical process of the right paramere shorter than the paramere body, in A. miyamotoanus and A. seonheulensis the wing-shaped sclerite only 3–4× as long as wide and in A. ater the needle-shaped sclerite is absent (Wang and Zheng 1982; Oh et al. 2018; Yasunaga 2023).

Other material. RUSSIA, Primorsky Terr. • 2♂ (see File S1).

(based on the specimens from ZIN and the original description). Length in male 4.5–5.4 mm, in female 5.3–5.8 mm. Head pale brown, apex of clypeus dark brown to black (Fig. 15D); antenna dark brown, extreme apex of antennal segment III paler; pronotum pale brown, sometimes widely darkened; scutellum usually uniformly brown to dark brown, apex of scutellum sometimes pale; clavus mostly brown to dark brown, corium yellow with brown to dark brown marking posteriorly or almost entirely dark brown to black, lateral margin of embolium brown, cuneus yellow or with red tinge with brown base and apex (Fig. 10G); pleura yellow to pale brown, sometimes with reddish tinge, metathoracic gland evaporative area whitish yellow; legs pale brown, femora with red tinge, hind femur with reddish brown or brown rings in apical part; tibiae with or without dark brown markings at base of spines and with pale brown to brown marking basally. — Male genitalia. Apical process of right paramere shorter than paramere body (Fig. 19I, J); wing-shaped sclerite ca. 4–5× as long as wide with straight margin, 0.2–0.3× as long as ventral sclerite, as wide as ventral sclerite, and wider than median sclerite; sublateral sclerite present, toothed, acute apically; needle-shaped sclerite present, slightly exceeding apex of wing shaped sclerite (Fig. 16I, J).

Japan (Yasunaga 2023), Primorskiy Territory, Russia (ZIN).

The specimens were collected from the inflorescences of broadleaf trees (Yasunaga 2023).

Among the specimens previously identified as Apolygus furvus and Apolygus hilaris, we found two males from Suchan (Primorsky Territory), which did not belong to those species. Both specimens are partially damaged but fit the description of Apolygus gotorum and their male genitalia are also very similar to those published by Yasunaga (2023). Therefore, we record A. gotorum for the first time from Russia (Primorskiy Territory). Among the specimens from the Russian Far East, A. gotorum is most similar to A. hilaris and A. subhilaris and pale representatives of A. furvus. However, all those species can be distinguished from A. gotorum externally. Apolygus furvus and A. hilaris differ from A. gotorum in the clypeus mostly dark brown to black (Fig. 15C, E), and A. subhilaris differs in the antennal segment I yellow.

Other material. RUSSIA • 1♂; holotype of Lygocoris (Apolygus) syringae Kerzhner, 1988; Primorsky Terr.: Kedrovaya Pad’ Nature Reserve, 43.067°N, 131.617°E, 01 Jul 1982, I. M. Kerzhner, Syringa amurensis Rupr. (Oleaceae), (ZISP_ENT 00015180) • 3♂♂, 2♀♀; paratypes of Lygocoris (Apolygus) syringae Kerzhner, 1988; Primorsky Terr. • JAPAN, RUSSIA, Primorsky Terr. • ♂, ♀ (see File S1).

Length in male 4.4–6.1 mm, in female 5.8 mm. Head yellow with dark brown to black clypeus (Fig. 15E); antennal segment I yellow with brown marking laterally and dorsally or mostly dark brown; antennal segment II mostly dark brown to black with yellow band at basal half or uniformly dark brown to black; pronotum yellow, scutellum brown, often with yellow apex; clavus yellow to brown; corium yellow with brown to dark brown marking posteriorly, lateral margin of embolium yellow to brown; cuneus yellow often with red tinge, with brown base and apex (Fig. 10H, I); pleura yellow to pale brown, sometimes with reddish tinge, metathoracic gland evaporative area yellow; coxae yellow sometimes with red tinge; femora yellow with red tinge in apical half or uniformly red, with dark red or reddish brown rings apically; tibia with dark brown markings at base of spines and with pale brown to brown marking basally. — Male genitalia. Apical process of right paramere shorter than paramere body (Fig. 19K, M); wing-shaped sclerite short, ca. 3–4× as long as wide with straight outer margin, ca. 0.2× as long as ventral sclerite, narrower than ventral sclerite and as wide as medial sclerite; sublateral sclerite present, toothed, acute; needle-shaped sclerite present, distinctly exceeding apex of wing-shaped sclerite but not reaching apex of ventral sclerite (18A, B).

Apolygus hilaris is known from the Russian Far East: Primorskiy Territory (Josifov and Kerzhner 1972; Kulik 1974; Kerzhner 1988b; Yasunaga 1992a; ZIN), Amur Territory – not confirmed, see Notes (Kulik 1965a, 1974; Josifov and Kerzhner 1972; Kerzhner 1988b), Khabarovsk Territory – not confirmed, see Notes (Kulik 1974; Josifov and Kerzhner 1972; Kerzhner 1988b). It also inhabits Japan (Horváth 1905; Josifov and Kerzhner 1972; Yasunaga 1992a, 2023; ZIN) and Korea (Josifov and Kerzhner 1972; Seong and Lee 2007; Oh et al. 2018).

Apolygus hilaris was recorded from Lonicera sp. (Caprifoliaceae) (ZIN), Syringae amurensis (Oleaceae) (Kerzhner 1988a, ZIN), Syringae reticulata (Oleaceae) (Yasunaga 1992a), Lespedeza sp. (Fabaceae) (Kulik 1965), Lespedeza bicolor (Fabaceae) (Kulik 1974; Kerzhner 1988a, 1988b), Maackiae amurensis (Fabaceae) (Kulik 1974).

Apolygus syringae was described by Kerzhner (1988a), but he mentioned that it differs from A. hilaris by the clypeus color. Yasunaga (1992a) synonymized A. syringae with A. hilaris, but later the same author resurrected the status of this species (Yasunaga 2023) based on the shape of the right paramere, number of teeth in the wing-shaped sclerite and the antennal segment II/ segment I ratio. We studied the specimens identified as A. hilaris and A. syringae preserved at ZIN, including the holotype of the latter. We compared their genital structures with the published figures, and we could not find any differences between those two species. In particular, the parameres are very similar. Most probably, the images of the parameres of those two species in Yasunaga (2023) were completed in the different projections, as the shape of the parameres of the A. syringae holotype is very similar with those of the A. hilaris specimens (Figs 9J–M, 19K–N). Therefore, we support the previous synonymy of A. syringae with A. hilaris. In this case we confirmed the specimen identification if we had the male genitalia available for examination. Therefore, we could only assign seven specimens from Japan and Primorsky Territory to A. hilaris. The drawings and images of vesica provided in the previous papers have the same structure of vesica as in the specimens examined by us (Josifov and Kerzhner 1972 – Korea; Kerzhner 1977, 1988a – Russian Far East; Yasunaga 1992a, 2023 – Japan; Seong and Lee 2007 – Korea).

Apolygus hilaris is similar to a number of other species externally. Among the specimens found in the Russian Far East, A. hilaris is most similar with A. subhilaris, but the latter differs in the clypeus mostly pale and dark brown to black only apically (Fig. 15L) and its vesica lacks needle-shaped sclerite (Fig. 17J). Apolygus hilaris is similar with the pale representatives of A. furvus externally, but A. furvus differs in the apical process of the right paramere subequal to the paramere body (Fig. 19E, G), and the long wing-shaped sclerite in vesica, which is 5–7× as long as wide, and longer than the needle-shaped sclerite (Fig. 16K). Apolygus hilaris can be confused with A. gotorum, but the latter differs in the clypeus mostly pale brown with dark brown to black apex (Fig. 15D) and the needle-shaped sclerite only slightly surpassing wing-shaped sclerite (Fig. 16I).

Type material. Holotype: RUSSIA • 1♂; Primorsky Terr.: Suchan [Partizansk], 43.139°N, 133.141°E, 16 Sep 1934, Palshkov, (ZISP_ENT 00016250) – Paratype: RUSSIA • 1♂; Khabarovsk Terr. (See File S1).

Length in male 4.5–4.8 mm. Head yellow to pale brown with brown markings and dark brown to black clypeus (Fig. 15F); antennal segment I yellow to pale brown, antennal segment II with yellow to pale brown basal half and its apical half brown to dark brown; pronotum dark brown to black; scutellum entirely dark brown to black or dark brown to black with pale brown apex; hemelytron including lateral margin of embolium uniformly dark brown to black (Fig. 10J); pleura dark brown to black, metathoracic scent gland evaporative area yellow; legs mostly yellow with red tinge, femora red, bands in apical half indistinct, markings at base of spines dark brown to black, at least bases of middle and hind femora brown. — Male genitalia. Apical process of right paramere subequal to paramere body (Fig. 19O, P); wing-shaped sclerite ca. 5–6× as long as wide with concave outer margin, subequal to 0.3–0.35× of ventral sclerite, as wide as lateral sclerite and wider than median sclerite; sublateral sclerite present, toothed, rounded, needle-shaped sclerite present (Fig. 18C, D).

Primorskiy Territory (Kerzhner 1977, 1988b; Miyamoto et al. 1994; ZIN), Khabarovsk Territory (Kerzhner 1977, 1988b; ZIN), Kuril Islands – not confirmed, see Notes (Kerzhner 1988b; Kerzhner and Marusik 1997; Kerzhner et al. 2004; Kanyukova and Marusik 2006). Records from Kuril Islands by Kerzhner (1977, 1978) refer to A. shikotansp. nov. This species was also recorded from Korea (Seong and Lee 2007; Oh et al. 2018) and Japan (Yasunaga 2023). However, at least some of the specimens collected in Japan belong to A. shikotansp. nov. (see Notes), and the male genitalia of the specimens from Korea were not published.

Kerzhner (1988b) mentioned that Apolygus infamis was collected from Phyllodendron amurense Rupr. and Phyllodendron sachalinense (Fr. Schmidt) Sarg. (Araceae), but this information is absent on the labels currently assigned to this species and can be erroneous. Apparently, the record from Phyllodendron sachalinense refers to Apolygus shikotansp. nov., because Kerzhner (1978) mentioned that the specimens from the type locality of this species (Malokurilskoe, Shikotan Island) were collected from this plant.

Apolygus infamis was described from the paratypes of A. furvus by Kerzhner (1977). We found that in the type series there are at least two species from Shikotan Island which differ in the shape of the right paramere and wing-shaped sclerite. We describe the second species as new to science, Apolygus shikotansp. nov. The records of A. infamis of Kerzhner and Marusik (1997) and Kanyukova and Marusik (2006) from Iturup, Kunashir and Shikotan Islands might also refer to A. shikotansp. nov. Therefore, we could reliably assign only two specimens to A. infamis. The drawing of vesica in Kerzhner (1988b) is more similar to A. shikotansp. nov. The genitalia illustrated in Yasunaga (2023) are also more similar to A. shikotansp. nov., and the record of A. infamis from Japan can be erroneous. Seong and Lee (2007) and Oh et al. (2018) recorded A. infamis from Korea, however, they did not provide illustrations of male genitalia of this species, therefore, the distribution of this species in Korea cannot be confirmed.

Among the species known from the Russian Far East, Apolygus infamis is similar to A. furvus and A. shikotansp. nov., but those two species differ in the wing-shaped sclerite, which is ca. 0.75× as long as ventral sclerite (Figs 16G, 16K, 17F). Apolygus shikotansp. nov. also differs in the apical process of the right paramere subequal to the half of the paramere body (Fig. 19W). Among the black congeners, A. atrobellus, A. miyamotoanus, A. nigricans, and A. seonheulensis differ from A. infamis in the apical process of the right paramere shorter than the paramere body (Wang and Zheng 1982; Oh et al. 2018; Yasunaga 2023). Apolygus atrobellus can be also differentiated in the absence of the needle-shaped sclerite. Among the species with the elongate apical process of the right paramere, Apolygus ater differs in the femora mostly dark brown, and Apolygus furvellus differs in the longer wing-shaped sclerite, ca. 7–8× as long as wide (Yasunaga 2023). Apolygus sinicus also has dark coloration but differs in the presence of Y-shaped sclerite on scutellum (Zheng and Wang 1983).

Other material. Belarus, Finland, Kazakhstan, Lithuania, Mongolia, Poland, Serbia, Russia, Altai Terr., Amur Prov., Arkhangelsk Prov., Bryansk Prov., Irkutsk Prov., Jewish Prov., Khabarovsk Terr., Khanty-Mansi Distr., Leningrad Prov., Magadan Prov., Primorsky Terr., Pskov Prov., Ryazan Prov., Samara Prov., Tula Prov., Yaroslavl Prov., Zabaikalsky Terr. • many ♂♂, ♀♀ (See File S1).

Length in male 4.8–5.4 mm (European form), 5.1–5.5 mm (Asian form), in female 4.7–5.2 mm (European form), 4.9–5.5 mm (Asian form). Head yellow, clypeus entirely or mostly pale brown to dark brown (Fig. 15G, H); antennal segment I yellow; antennal segment II yellow with pale brown to brown apical half or less, sometimes basal 1/3 also pale brown to brown; pronotum yellow sometimes pale brown or brown basally and often with brown to dark brown markings around calli, sometimes mostly brown to dark brown; scutellum varying from uniformly yellow to mostly brown to dark brown with yellow apex; clavus pale brown to dark brown, corium yellow, with brown to dark brown marking posteriorly, usually not reaching embolium, rarely reaching embolium only posteriorly; lateral margin of embolium brown to dark brown; cuneus yellow, brown to dark brown basally, pale apically (Fig. 11A–D); pleura including metathoracic scent gland evaporative area yellow; legs mostly yellow, at least hind femur with red or brown rings apically, sometimes most part of hind femur with red tinge; tibia yellow with dark brown to black markings at bases of spines and dark brown or red brown marking basally. — Male genitalia. Apical process of right paramere subequal to paramere body (Fig. 19S–V); sublateral sclerite present, toothed, acute apically; needle-shaped sclerite surpassing secondary gonopore and apex of wing-shaped sclerite, but not reaching apex of ventral sclerite; wing-shaped sclerite with straight outer margin, as wide as lateral sclerite and wider than median sclerite. European form: wing-shaped sclerite ca. 4–5× as long as wide, needle-shaped sclerite subequal to wing-shaped sclerite (Fig. 18E, F). Asian form: wing-shaped sclerite ca. 2–3× as long as wide, distance between wing-shaped sclerite and needle-shaped sclerite apices 0.2–0.3× as long as needle-shaped sclerite (Fig. 18, J).

Apolygus limbatus can be considered as trans-Palearctic, but it does not live in the southern parts of Russia (Vinokurov et al. 2024). This species is known from the Russian Far East, i.e. Amur, Khabarovsk, Primorsky Territories (Kerzhner 1988b; Vinokurov et al. 2010) and East Asia, i.e. Korea (Kim and Jung 2016; Oh et al. 2018).

Apolygus limbatus lives on Salix spp. (Kerzhner and Jaczewski 1964; Kulik 1965a; Kerzhner 1988b; ZIN), it was also recorded from Populus sp. (Kulik 1965b, 1974; Wagner 1974).

According to Kerzhner and Josifov (1999), Apolygus limbatus is known from Japan, but it is absent in the species list for Japan (Yasunaga 2023).

We found that the specimens identified as A. limbatus have two types of sclerotization in vesica and this corresponds to the distribution: Europe (reaching Ural Mountains) and Asia (Fig. 18E, F, I, J). The drawing of vesica in the key to the Heteroptera of the European part of the USSR (Kerzhner and Jaczewski 1964) corresponds to the European form. Those groups can represent two separate species; however, we did not find any differences in the shape of the parameres and habitus between them, and the molecular data were insufficient to resolve this problem. More specimens from those groups and nuclear markers should be included in the analysis. Therefore, we refrain from any taxonomic decisions pending additional molecular data. Apolygus limbatus is most similar to A. maackiae in coloration, but the latter differs in the apex of cuneus dark brown to black, yellow outer margin of embolium and yellow legs without reddish tinge. Additionally, in A. maackiae wing-shaped sclerite is absent and its ventral sclerite has needle-shaped outgrowth (Fig. 18G, H).

Type material. Holotype: RUSSIA • 1♂; Primorsky Terr.: Vladivostok, 43.11666°N, 131.9°E, 12 Aug 1964, Kulik, Maackia amurensis Rupr. (Fabaceae), (ZISP_ENT 00016249) – Paratype: RUSSIA • 1♂; Primorsky Terr. Other material. RUSSIA, Primorsky Terr. • 5♂♂ (See File S1).

Body length in male 4.0–4.6 mm; head yellow with at least apical half of clypeus dark brown to black (Fig. 15I); antennal segment I yellow, often with dark brown stripe ventrally; antennal segment II mostly dark brown to black, usually with yellow to pale brown ring in basal half, sometimes entire basal half yellow to pale brown; pronotum with anterior part yellow and posterior part brown to dark brown, sometimes uniformly yellow; scutellum brown to dark brown; clavus mostly or entirely brown to dark brown; corium mostly yellow with brown to dark brown marking posteriorly, not reaching outer margin of hemelytron, sometimes corium mostly brown; lateral margin of embolium mostly yellow, pale brown to brown posteriorly; cuneus mostly yellow, with brown base and apex (Fig. 11E); pleura including metathoracic scent gland evaporative area yellow; legs yellow with dark brown markings at base of spines, bases of tibiae brown to dark brown. — Male genitalia. Apical process of right paramere shorter than paramere body (Fig. 19Q); wing-shaped sclerite absent; ventral sclerite bifurcate with one apex distinctly wider than needle-shaped sclerite, and second apex as wide as needle-shaped sclerite; needle shaped-sclerite surpassing sublateral sclerite; sublateral sclerite rounded; median sclerite present, small, distinctly narrower than secondary gonopore; basal sclerite present, not reaching secondary gonopore (Fig. 18G, H).

Apolygus maackiae is recorded from Primorsky Territory (Kulik 1965b, 1974; Kerzhner 1988b) and from Japan (Yasunaga 2023).

Apolygus maackiae was initially recorded from Maackiae amurensis Rupr. (Fabaceae) (Kulik 1965b, 1974; Kerzhner, 1988b; ZIN). Several specimens of this species were also collected from Polygonum sp. (Polygonaceae) (ZIN).

This species is most similar to Apolygus limbatus in coloration. However, the latter differs in the legs often tinged with red, the cuneus not darkened apically (Fig. 11A–D) and the presence of the wing-shaped sclerite (Fig. 18E, I).

Holotype: RUSSIA • 1♂; Sakhalin Prov.: Malokurilskoe, Shikotan Mt., Shikotan Island, 43.85°N, 146.81666°E, 20 Aug 1973, I. M. Kerzhner, 1♂ (ZISP_ENT 00016047) (ZIN). Paratypes: RUSSIA • 4♂♂, ♀; Sakhalin Prov. (See Data S1).

Length in male 4.4–4.8 mm. Head pale brown with brown stripes and dark brown to black clypeus or mostly dark brown to black (Fig. 15J, K); basal half of antennal segment II pale brown to brown, apical half of antennal segment II dark brown to black; pronotum and scutellum dark brown to black; pleura dark brown to black; metathoracic scent gland evaporative area yellow; hemelytron mostly dark brown to black, lateral margin of embolium brown to dark brown; cuneus uniformly dark brown to black or pale brown medially (Fig. 11F); legs yellow; femora red; coxa yellow or red; markings at base of spines dark brown to black; bases of at least middle and hind femora brown; apical process of right paramere subequal to paramere body (Fig. 19W); wing-shaped sclerite surpassing sublateral sclerite, ca. 7–8× as long as wide with concave outer margin, 0.75× as long as ventral sclerite, as wide as lateral sclerite and wider than median sclerite; inner margin of lateral sclerite concave; sublateral sclerite present, toothed, rounded, wider than secondary gonopore width; needle-shaped sclerite present, as long as wing-shaped sclerite, surpassing secondary gonopore, not reaching apex of ventral sclerite (Fig. 17F, G).

MALE. Length in male 4.4–4.8 mm. — Coloration Head pale brown with brown stripes and dark brown to black clypeus or mostly dark brown to black (Fig. 15J, K); antennal segment I pale brown to brown, basal half of antennal segment II pale brown to brown, apical half of antennal segment II brown to dark brown, antennal segments III and IV dark brown, segment III with pale base; pronotum and scutellum dark brown to black, pleura dark brown to black, evaporatorium yellow; hemelytron mostly dark brown to black, cuneus uniformly dark brown to black or pale brown medially; membrane brown (Fig. 11F); legs yellow, femora red, coxa yellow or red, markings at base of spines dark brown to black, at least bases of middle and hind femora brown; tarsal segments I and II yellow to pale brown, segment III brown. Surface and vestiture. Dorsum shining, covered with pale simple setae. — Structure Body ca. 3.2× as long as wide, ca. 1.8–1.9× as long as pronotum width; head ca. 2.9–3.2× as wide as long, in lateral view head ca. 1.3–1.4× as long as high; antennal segment I 1.2–1.5× as long as vertex, ca. 0.5–0.6× as long as head width; antennal segment II ca. 2.8–3.1× as long as segment I, ca. 1.6× as long as head width, ca. 0.9× as long as pronotum width; pronotum ca. 1.6–1.8× as wide as head, ca. 1.8–1.9× as wide as long. — Male genitalia. Apical process of right paramere shorter than paramere body (Fig. 19W); wing-shaped sclerite surpassing sublateral sclerite, ca. 7–8× as long as wide with concave outer margin, ca. 0.75× as long as ventral sclerite, as wide as lateral sclerite and wider than median sclerite; inner margin of lateral sclerite concave; sublateral sclerite toothed, rounded, wider than secondary gonopore; needle-shaped sclerite present, as long as wing-shaped sclerite, surpassing secondary gonopore, not reaching apex of ventral sclerite (Fig. 17F, G). — FEMALE. Coloration. Similar to male. Cuneus mostly dark brown, pale brown medially. — Structure. Body 1.8× as long as pronotum width; head 3.6× as wide as long, in lateral view head ca. 1.5× as long as high; antennal segment I 1.2× as long as vertex, 0.4× as long as head width; pronotum ca. 1.7× as wide as head, ca. 1.8× as wide as long. — Genitalia. Dorsal labiate plate width subequal to its length, sclerotized ring of dorsal labiate plate ca. 4× as long as wide, distance between rings ca. 0.25× as long as sclerotized ring width (Fig. 7C, D).

Apolygus shikotansp. nov. was recorded from a single location in the Kuril Islands, Russian Far East), however, at least some specimens of A. infamis from Japan can be attributed to this species too (see Notes for A. infamis).

The specimens of this species were collected from Phyllodendron sachalinense (Fr. Schmidt) Sarg. (Araceae) (Kerzhner 1978).

This species is named after Shikotan Island, where its specimens were collected.

We found that there are two species in the type series of Apolygus infamis, and only two specimens from the same locality belong to A. infamis. We describe the second species as new to science, A. shikotansp. nov., because it does not fit a description of any other species known from this genus. There are only a few species with dark brown to black color of hemelytron without any stripes or markings on clavus and corium, i.e., Apolygus ater, A. atrobellus, A. furvellus, A. furvus, A. infamis, A. miyamotoanus, A. nigricans, A. rubriceps, and A. seonheulensis. In A. ater, A. furvellus, A. furvus, and A. infamis the apical process of right paramere is subequal to the paramere body (Fig. 19E–H, O, P). In Apolygus atrobellus, A. furvellus, A. furvus, A. miyamotoanus, and A. nigricans sublateral sclerite diameter shorter than the secondary gonopore (Fig. 16K). Apolygus atrobellus differs in the absence of the needle-shaped sclerite, and in A. seonheulensis the needle-shaped sclerite does not surpass the secondary gonopore. In all those species, except for A. infamis and A. seonheulensis, the outer margin of wing-shaped sclerite is straight. Apolygus infamis, A. nigricans and A. seonheulensis additionally differ in the wing-shaped sclerite short, not surpassing the sublateral sclerite (Wang and Zheng 1982; Yasunaga 1992a; Oh et al. 2018; Yasunaga 2023).

Other material. RUSSIA • ♂; holotype of Lygocoris (Apolygus) nigrovirens Kerzhner, 1988; Sakhalin Prov.: Tret’yakovo, Kunashir Island, 43.98889°N, 145.64167°E, 03 Aug 1973, I. M. Kerzhner, 1♂ (ZISP_ENT 00015835) • 7♂♂, 4♀♀; paratypes of Lygocoris (Apolygus) nigrovirens Kerzhner, 1988; Primorsky Terr, Sakhalin Prov. • China, JAPAN, Mongolia, North Korea, South Korea, Ukraine, Russia • many ♂♂, ♀♀ (See File S1).

Length in male 4.8–6.3 mm, in female 4.7–6.3 mm. Head from uniformly yellow or green to mostly brown with yellow or green markings, clypeus from uniformly yellow or green to uniformly dark brown to black (Fig. 15Q–W); antennal segment I from uniformly yellow or green to brown; antennal segment II uniformly yellow or green, sometimes brown to dark brown apically and rarely also basally; pronotum from uniformly yellow or green to mostly brown with yellow or green posterior margin, calli often yellow to pale brown; scutellum from uniformly yellow or green to mostly brown with yellow to green apex, sometimes lateral angles also yellow to green; hemelytron often yellow to green with pale brown to brown marking on posterior part of corium and very apex of corium sometimes also brown to dark brown; sometimes clavus and corium with brown stripes or mostly brown to dark brown (Fig. 12); lateral margin of hemelytron pale brown to dark brown (see from lateral view); pleura, varying from uniformly yellow or green to mostly brown with yellow or green markings, metathoracic scent gland evaporative area yellow or green; sometimes coxae, femora and tibiae uniformly yellow to green, sometimes hind femora with pale brown to brown bands apically and spines on tibia with dark brown to black markings at base. — Male genitalia. Apical process of right paramere ca. 0.2–0.25× as long as paramere body (Fig. 19Y). Wing-shaped sclerite ca. 4–5× as long as wide with straight outer margin, ca. 0.8× as long as ventral sclerite, as wide as lateral sclerite and wider than median sclerite; sublateral sclerite small and toothed or absent; median sclerite present, thin; needle-shaped sclerite absent (Fig. 17A, C).

Apolygus spinolae is a trans-Palearctic species, known from Western Europe to Kuril Islands and Japan. It was recorded from the Caucasus but was not recorded from Iran (Zamani and Hosseini 2020). In Central Asia A. spinolae was recorded from Kazakhstan, Kyrgyzstan, Uzbekistan (Kerzhner and Josifov 1999). It is also abundant in China (Kerzhner and Jaczewski 1999; Zamani and Hosseini 2020; Zhang et al. 2020; Lu et al. 2024). The species is also known from Canada and the USA (Kelton 1971) and can be invasive.

Polyphagous. In particular, its specimens were collected from Thermopsis sp., Thermopsis lupinoides, Lespedeza sp. (Fabaceae), Artemisia spp., Tanacetum sp. (Asteraceae), Rosaceae, Urtica sp. (Urticaceae) (Kelton 1971; Kerzhner 1978, 1988a; Yasunaga 1992a). The species is considered as a pest of many plants, e.g., Camellia sinensis (tea plant), cotton, vegetables, fruits (Yasunaga 1992a; Zhang et al. 2020; Lu et al. 2024). It was also recorded as omnivorous (Lu et al. 2024).

Meyer-Dür (1841) described the new species Capsus spinolae Meyer-Dür, 1841, and the same author (Meyer-Dür 1843) described Capsus lucorumMeyer-Dür 1843, both from Switzerland. He noted that C. lucorum is similar to C. spinolae but differs in the brighter coloration, absence of marking above cuneus and darker membrane. There were several specimens in the type series of the species described by Meyer-Dür (1941, 1943). Kerzhner (1996) designated lectotypes for both species, female in each case, preserved at the American Museum of Natural History. We requested digital images of the lectotypes, however, at this moment they are lost, and the paralectotypes of both species are very similar to each other, having uniformly yellow dorsum and clypeus, which also corresponds to the original description. However, paralectotype of A. spinolae have slightly darkened apex of cuneus (Fig. 14B, F), although it was not mentioned in the original description.

In the consequent keys those two species were differentiated using the presence and absence of the marking on cuneus apically (Wagner and Weber 1964; Wagner 1974; Kerzhner and Jaczewski 1964; Yasunaga 1992a; Vinokurov and Kanyukova 1995; Seong and Lee 2007). Kerzhner (1988a) and Vinokurov and Kanyukova (1995) also mentioned that two species can be differentiated in the mostly darkened or mostly pale clypeus in A. lucorum and A. spinolae respectively. Stål (1858) described a new species Deraeocoris nigro-nasutus from Siberia (Irkutsk), but he did not compare it with A. lucorum and A. spinolae. Lygus (Neolygus) malaisei was described by Lindberg (1925) from Kamchatka Peninsula, but he did not compare it with any species placed in Apolygus by that time. Kerzhner (1988a) described Lygocoris (Apolygus) nigrovirens from the Russian Far East and he mentioned that all five species were very similar to each other and differed in the coloration. In particular, A. nigrovirens differed from A. lucorum and A. spinolae in the dark markings on clavus and larger marking on the apex of cuneus. In A. nigronasutus the outer margin of corium was black and clypeus was mostly black, the pronotum, scutellum and hemelytron were generally paler, and tarsal segment III was entirely dark, whereas in A. nigrovirens the outer margin of corium was pale, the clypeus was mostly pale, the pronotum, scutellum and hemelytron were darker, and half of tarsal segment III was dark. Apolygus malaisei was darker than A. nigrovirens, but there were specimens assigned to both species which were very similar in coloration. He did not provide any characters in genitalic structures which can be used for the species differentiation. Yasunaga and Yasunaga (2000) mentioned that A. nigronasutus has the needle-shaped sclerite and they did not provide the illustration or any literature reference. We consider this a mistake, because Kerzhner (1988a) did not mention this character while comparing it with A. nigrovirens, and he noted that he could not find any differences in male genitalia in all five species. We also did not find any needle-shaped sclerite in the specimens identified as A. nigronasutus in the ZIN collection. Examination of the syntypes of this species cannot provide any additional information on the male genitalia structures, because they are females (Stål, 1858; Kerzhner and Jachewski, 1999). The characters in coloration were used in the keys of Kerzhner (1988b) and Vinokurov and Kanyukova (1995). Yasunaga (1992b), Seong and Lee (2007) and Kim and Jung (2016) additionally used labium length to differentiate A. spinolae and A. nigrovirens. According to Yasunaga (1992b) and Seong and Lee (2007), the labium reaches hind coxae in the former and does not reach them in the latter. However, in the key of Kim and Jung (2016) the labium reaches hind coxae in A. nigrovirens, whereas it is shorter in A. spinolae. We examined the large collection preserved at ZIN and dissected males belonging to numerous series of each species. We found that the coloration is very variable in all five species, and it is impossible to split them into the discrete morphs based on the characters mentioned by the previous authors. In particular, it was not possible to find the discrete states for the coloration of cuneus, which can be entirely green (Figs S12O, S15C, S16C, I, O, U, S17C, I, U), slightly darkened apically (Figs S12V, S14J, P, S17O, 18C, I) or having distinct dark brown marking apically of various size (Figs S12C, I, S13C, H, N, T, S14D, W, S18O). The same is true for the color of clypeus (Figs S12–S18). Additionally, the marking on clypeus cannot be used for the discrimination of A. lucorum from A. spinolae, because the representatives of type series of both species have entirely pale clypeus (Fig. 14B, F). The length of the labium cannot be used to separate A. nigrovirens and A. spinolae, because its position with respect to the middle and hind femora depends on the position of the head. Kerzhner (1988a) did not mention this character in the original description, and it is unclear how Seong and Lee (2006) and Kim and Jung (2016) associated the labium length with the characters provided in the original description.

Jung et al. (2011) and Kim and Jung (2018a) differentiated A. lucorum, A. nigrovirens, A. spinolae and A. watajii in the shape of sclerites in vesica. However, in those two papers the authors use different color criteria to separate the species and the characters in the sclerites corresponding to the color morphs are also different. In particular, according to Jung et al. (2011) in A. lucorum clypeus is mostly dark and the wing-shaped sclerite has teeth, whereas in A. nigrovirens and A. spinolae the clypeus is mostly pale and the wing-shaped sclerite is smooth. It is unclear from this work how they differentiated A. nigrovirens and A. spinolae from each other. According to Kim and Jung (2018a), A. lucorum and A. spinolae differ in the following characters: in the former, the apex of cuneus is pale, the wing-shaped sclerite is broad and the sublateral sclerite is present, whereas in the latter the apex of cuneus is darkened, the wing-shaped sclerite is slender and the sublateral sclerite is absent

The color morphs associated with the species names in Jung et al. (2011) were erroneous, because A. lucorum and A. spinolae do not differ in the clypeus color, which is confirmed by the images of the paralectotypes (Fig. 14B, F) and this character has not been mentioned in the original description. After examination of genitalia belonging to the different color morphs, we could not find any specimen having the wing-shaped sclerite without teeth, however, we agree that the teeth size is variable (Figs S12–S18). Additionally, the teeth are most obvious when the vesica is illustrated in the right lateral view, whereas in Jung et al. (2011) the image illustrating the smooth wing-shaped sclerite shows the vesica rotated towards the dorsal view (fig. 3F in Jung et al. 2011). We also imaged the vesica in the same rotated view and found that the teeth are less obvious in this position, even if they are distinct in right lateral view (Figs S12T, S14B, O). This character was also mentioned in Yasunaga (1992a) in the comparison of A. spinolae with A. lucorum, but he did not mention it in the key for Japanese Apolygus species published the same year (Yasunaga 1992b).

Although some authors used the shape of wing shaped sclerite to separate A. lucorum and A. spinolae, they did not provide any particular ratio, using the descriptive terms “broad” and “slender” (Yasunaga 1992; Kim and Jung 2019). Examination of the specimens from the large part of the Palearctic showed that the shape of this sclerite is variable and does not correspond to the color morphs (Figs S12–S18). Sublateral sclerite also vary and can be absent (e.g., Fig. S12B, H, U), pale (mostly membranous) (e.g., Figs S13M, 16B, T) and distinct (e.g., Figs S13B, S16I, N). The distinct sublateral sclerite was usually present in the specimens with pale apex of cuneus and without additional markings on dorsum (A. lucorum) (e.g., Figs S15B, S16H, S17H), but the representatives of the same color morph sometimes do not have this sclerite (Fig. S17N) and it is also present in other color morphs (Fig. S13B). The presence and absence of this sclerite also does not correspond to the clades in the phylogenetic trees. Additionally, the sublateral sclerite can be absent and present within A. watajii. It is depicted in the images provided by Seong and Lee (2007) and in the specimens examined by us (Fig. 17L, M), however, Kim and Jung (2019) reported its absence in the same species but did not comment on the previous work. In those two papers and the specimens examined by us the shape of the wing-shaped sclerite is the same for A. watajii, and it is very likely that all those specimens belong to the same species.

In the work of Kim and Jung (2019) the sequences of A. nigrovirens from Jung et al. (2011) were not included to the analysis without any explanation and it is unclear how they differentiate this species from A. lucorum and A. spinolae. Additionally, the specimen of A. spinolae in the image provided in Kim and Jung (2019), has a dark marking on clavus. According to the original description and the key to Far East (Kerzhner 1988a, 1988a), A. nigrovirens had this marking, whereas A. spinolae did not. Kim and Jung (2019) did not comment on this character.

Overall, we could not find any discrete characters in male genitalia in species group, comprising A. lucorum, A. malaisei, A. nigronasutus, A. nigrovirens, and A. spinolae. Both molecular and morphological characters indicate that the specimens previously identified as those five species represent a single polymorphic species. The examination of the previous literature shows that the criteria on how the researchers assign the specimens to those species are different in the different studies, and we should rely on the original descriptions and types to treat those species. The original description and the paralectotypes show only a single difference between A. lucorum and A. spinolae, which is the coloration of the apex of cuneus. The examination of the numerous specimens from the most part of the Palearctic shows that this character is variable and cannot be considered as discrete (Figs S12–S18). We could not examine the lectotypes and based on the original descriptions they should be mostly green with darkened membrane and the tarsi dark brown to black apically (Meyer-Dür 1941, 1943). The examination and dissection of those specimens will not provide any additional information, because they are females, and the differences in the female genitalia have never been reported for those two species, and we could not find them as well. The differences of the sclerite shapes are also not discrete and do not correspond to the color morphs.

Other species which have similar or the same male genitalia as A. spinolae and green or yellow coloration are Apolygus atrosignatus, A. halophilus, A. nepius, A. olivarius, A. rhamnicola, and A. watajii (Wagner and Weber 1964; Yasunaga and Yasunaga 2000; Yasunaga 2023). All those species were previously separated using coloration, which is unreliable, considering the color variation range in A. spinolae. Among them A. watajii can be separated from A. spinolae in the wing-shaped sclerite 2–3× as long as wide, and A. nepius has wide ventral sclerite (Yasunaga and Yasunaga 2000) (Fig. 17L). According to Yasunaga (2023)A. halophilus has the antennal segment III distinctly shorter than the head width whereas in A. spinolae it is as long as the head width (Yasunaga 2023). According to Yasunaga and Yasunaga (2000)A. atrosignatus, can be differentiated from A. spinolae in the longer antennal segment III. Apolygus olivarius differs from A. lucorum in the antennal segments II/IV ratio (Yasunaga 2023). However, antennal segments III and IV are sometimes shrunken, and it is impossible to measure their length correctly. Although A. rhamnicola is an European species, very little is known about its morphology. According to Wagner and Weber (1964), it differs from A. lucorum and A. spinolae in the presence of the dark markings at the bases of spines on tibiae, however, many specimens of A. spinolae also have them, but those specimens usually have darker coloration of dorsum (e.g., A. nigrovirens, A. nigronasutus, A. malaisei color morph). We dissected the specimen from the ZIN collection which was identified as A. rhamnicola with the coloration fitting the description of this species. The parameres and vesica are very similar to A. spinolae. The dissected specimen has a distinct sublateral sclerite with three rows of spines. However, this condition also occurs in the specimens of A. spinolae without markings at the base of the tibial spines. Therefore, we consider the status of A. rhamnicola as doubtful, and it should be tested using the nuclear markers.

Non-type material. Japan, Russia: Amur Prov., Primorsky Terr. • 7♂♂, 3♀♀.

Length in male 4.7–5.2 mm, in female 5.1 mm. Head yellow with yellow clypeus, sometimes clypeus brown apically (Fig. 15L); antennal segment I mostly yellow, often brown to dark brown apically and with brown to dark brown marking ventrally; antennal segment II brown to dark brown, sometimes with yellow to pale brown ring in basal half; pronotum yellow, scutellum varying from uniformly yellow to brown, corium yellow to pale brown with brown to dark brown marking posteriorly, sometimes mostly brown; lateral margin of embolium brown; cuneus yellow or with red tinge with brown base and apex; pleura yellow, sometimes with reddish tinge, metathoracic scent gland evaporative area whitish yellow; coxae yellow, sometimes with red tinge; femora yellow, often with red tinge, with red or brown rings in apical half; dark brown markings at base of spines on tibiae present; base of tibiae with small pale brown to brown marking. — Male genitalia. Apical process of right paramere twice shorter than paramere body (Fig. 19AA); wing-shaped sclerite ca. 4–5× as long as wide with straight outer margin, surpassing sublateral sclerite, subequal to half of ventral sclerite, as wide as ventral sclerite and wider than median sclerite; sublateral sclerite present, toothed, triangular with acute angle; needle-shaped sclerite very short or indistinct (Fig. 17J).

Previously this species was recorded from Japan (Yasunaga 1992b, 2023) and South Korea (Seong and Lee 2007; Kim and Jung 2016; Oh et al. 2018). Here we report it for the first time from Russia: Primorsky Territory and Amur Province (ZIN).

In Korea this species was recorded from Lespedeza bicolor (Fabaceae) (Seong and Lee 2007).

All specimens of this species included in this work were previously identified as Apolygus hilaris. The two species are very similar externally. Apolygus hilaris can be differentiated by the dark brown to brown clypeus (Fig. 15E). Additionally, its vesica has a long needle-shaped sclerite, which is distinctly longer than the wing-shaped sclerite (Fig. 18A, B). The vesica structure of A. subhilaris specimens examined by us corresponds to that depicted in Yasunaga (1992a) and Seong and Lee (2007).

Among the vouchers used for the molecular work, we found two specimens from Primorsky Territory which are very similar to A. subhilaris in coloration (M197, M124; Fig. 11I, J), however, they have the needle-shaped sclerite in the vesica reaching the secondary gonopore (Fig. 17H, I). There are several species which have similar coloration and illustrations of vesica were not published for them and those three specimens can belong to one of them, i.e., Apolygus angustus (Zheng & Wang, 1983), Apolygus kosempoensis (Poppius, 1915), Apolygus myittae (Distant, 1904), Apolygus triangulus (Zheng & Wang, 1983), Apolygus umbratus (Poppius, 1914), or can represent a new species. Therefore, we publish the illustration of habitus and male and female genitalia for those specimens which can be useful for the future revisions of Apolygus.

Type material. Holotype: RUSSIA • 1♂; Primorsky Terr.: Khasan Station, Golubiny Utes Tract, 42.417°N, 130.666°E, 24 Aug 1982, I. M. Kerzhner, Lespedeza bicolor Turcz. (Fabaceae), (ZISP_ENT 00015170) – Paratypes: JAPAN, RUSSIA, Primorsky terr • 55♂♂, 38♀♀, 5 unknown • Other material. Japan, South Korea, RUSSIA, Primorsky Terr • 5♂♂, ♀ (See File S1).

Length in male 4.3–5.1 mm, in female 4.3–5.0 mm. Head yellow, sometimes with pale brown to brown or red markings, clypeus dark brown (Fig. 15N); antennal segment I yellow to pale brown; antennal segment II often mostly yellow to pale brown and brown to dark brown apically, sometimes mostly brown to dark brown, yellow to pale brown basally; pronotum color varying from uniformly yellow to mostly brown with yellow to pale brown markings, often with dark brown marking around calli; scutellum mostly yellow, often with large subrectangular red or brown marking covering basal and medial parts, rarely mostly brown to dark brown with yellow apex; clavus varying from yellow to dark brown; corium varying from yellow with brown to dark brown marking posteriorly to mostly dark brown, often brown to dark brown with yellow marking medially; lateral margin of embolium brown to dark brown; cuneus yellow, brown to dark brown basally and apically, sometimes with red tinge (Fig. 13A–C); pleura yellow with red or brown markings, metathoracic scent gland evaporative area yellow; legs mostly yellow; femora with red tinge at least in apical half, often with pale brown to brown bands near apex; dark brown markings at base of spines on tibiae present; base of tibiae with small pale brown to brown marking. — Male genitalia. Apical process of right paramere 0.3× as long as paramere body (Fig. 19AE, AF); wing-shaped sclerite present, concave, without teeth, ca. 7–8× as long as wide, reaching apex of lateral sclerite, wider than ventral and median sclerites; ventral sclerite slightly surpassing secondary gonopore, distinctly shorter than wing-shaped sclerite, as wide as median sclerite, inner margin of lateral sclerite straight; sublateral sclerite present, subrectangular, its inner margin toothed, needle-shaped sclerite absent (Fig. 18K, L).

Apolygus subpulchellus is recorded from Primorsky Territory (Kerzhner 1988a; ZIN), Korea (Oh et al. 2018; ZIN), Japan (Kerzhner 1988a; ZIN).

Lespedeza bicolor (Kerzhner 1988a, 1988b).

Yasunaga (2023) described A. habilis, which is very similar to A. subpulchellus. The differences separating those species are very small, e.g., larger body, pale coloration, thicker parameres, tumid hypophysis of the right paramere, slender lateral sclerite and more developed wing-shaped sclerite that is more notched, vesica with denser field of spines below gonopore in A. habilis. Those differences can represent the intraspecific variation. We examined the male genitalia of all the series preserved at ZIN, including those collected in Japan and Korea, and found that all of them have wing-shaped sclerite more sinuate (more notched), similar to A. habilis, and we did not find any noticeable variation in the shape of lateral sclerites or parameres. Therefore, we did not find any discrete differences in the specimens assigned to A. subpulchellus preserved at ZIN, including those collected in Japan and Korea and treat all of them as this species. The status of A. habilis as a separate species is questionable.

Type material. Paratypes: JAPAN, RUSSIA, Primorsky Terr. • 6♂♂, 4♀♀ • Other material. China, Russia, Khabarovsk Terr., Primorsky Terr. • many ♂♂, ♀♀ (See File S1).

Length in male 5.1–5.5 mm, in female 5.3–5.6 mm. Head mostly yellow green or green, clypeus usually uniformly dark brown to black, sometimes only its apical half dark brown to black (Fig. 15O, P); apex of antennal segment II brown to dark brown; pronotum and scutellum yellow green or green, with brown paired markings on posterior part laterally; hemelytron yellow green or green, corium with brown marking posteriorly; lateral margin of embolium pale brown to dark brown; cuneus uniformly green, not darkened posteriorly (Fig. 13D–F); pleura, including metathoracic scent gland evaporative area yellow to green; legs yellow to green, without dark markings, spines on tibia without dark markings at base. — Male genitalia. Apical process of right paramere 0.3–0.4× as long as paramere body (Fig. 19AG). Wing-shaped sclerite ca. 2–2.5× as long as wide, subequal to half of ventral sclerite in length, wider than lateral and median sclerites; inner margin of lateral sclerite convex, outer margin of lateral sclerite concave; sublateral sclerite small and toothed; median sclerite present, thin, needle-shaped sclerite absent (Fig. 17L, M).

In Russia Apolygus watajii was recorded from Primorskiy Territory (Yasunaga and Yasunaga 2000; ZIN). Here we report it from Khabarovsk Territory for the first time (ZIN). This species is also known from Japan (Yasunaga and Yasunaga 2000; Yasunaga 2023; ZIN), South Korea (Yasunaga and Yasunaga 2000; Kim and Jung 2016; Oh et al. 2018), and we report it from northeast China (ZIN) for the first time.

In Korea this species was recorded from Persicaria spp. and Fagopyrum esculentum (Polygonaceae) (Seong and Lee 2007). In the ZIN collection the specimens were collected from Polygonum sp. (Polygonaceae) and Arthemisia vulgare (Asteraceae).

Yasunaga and Yasunaga (2000) described A. watajii and mentioned that this species often cannot be separated from A. lucorum externally and examination of the vesica is needed for the correct identification. We examined the specimens preserved at ZIN and found that A. watajii differs from A. spinolae in the shape of wing-shaped sclerite, which is 4–5× as long as wide in the former (Fig. 17L) and 2–3× as long as wide in the latter (Fig. 17A, C). Although the present molecular data show ambiguous results on whether A. watajii falls within A. spinolae or not, the differences in the wing-shaped sclerite are consistent, therefore, we treat it as a separate species. Examination of the ZIN collection showed that numerous specimens of A. watajii were identified as A. lucorum, and this species inhabit not only Primorsky Territory, but Khabarovsk Territory as well. We also found a specimen of this species collected in China.