Triozidus stackelbergi ( Loginova, 1967 ), 2025

Liao, Yi-Chang, Inoue, Hiromitsu & Percy, Diana M., 2025, The psyllid genus Triozidus Li, 1994 stat. rev. sensu novo (Hemiptera: Psylloidea: Triozidae) in East Asia is redefined with the addition of two new species from Taiwan inducing galls on the leaflet petiolules of Eleutherococcus trifoliatus (Araliaceae), Zootaxa 5727 (1), pp. 113-139 : 121-126

Triozidus stackelbergi ( Loginova, 1967) comb. nov.

( Figs 4–7 )

Trioza stackelbergi Loginova, 1967: 345 .

Heterotrioza ( Dyspersa) stackelbergi : Klimaszewski (1973: 248).

Triozidus acanthopanaicis Li, 1994: 85 , synonymised by Kwon & Kwon (2020: 220).

Heterotrioza acanthopanaicis : Li (2011: 1521).

Heterotrioza stackelbergi : Kwon & Kwon (2020: 220), Cho et al. (2022: 72) .

Lunatrioza stckelbergi [ sic] Kwon, Suh & Kwon, 2022: nomen nudum [conference poster, not a published work in the sense of the International Code of Zoological Nomenclature].

Material examined. KOREA • 4 ♂, 3♀; Yeong wol-gun, Jucheon-myeon, Jucheon-ri , Swimteo Park ; 37°26’09.3”N, 128°29’26.9”E; 3 Oct 2014; Jin-Yeong Choi leg.; NCHU, slide mounted, glycerol and ethanol . JAPAN • 6♀, 1 immature; Honshu, Nagano Pref., Kitasaku-gun, Minamimaki-mura , Nobeyama ; 35.93515 N, 138.46349 E, 1370 m; 16 Oct. 2018; Akihide Koguchi leg.; Eleutherococcus divaricatus (twig galls, flower galls); HIC, dry, slide mounted . 15♂, 14♀, 4 immatures; same data but 6. Oct. 2019; HIC, NCHU, dry, slide mounted and in ethanol . 20♂, 27♀, 18 immatures; Honshu, Nagano Pref., Kitasaku-gun, Minamimaki-mura , Itabashi ; 35.97757 N, 138.47251 E, 1350 m; 6 Oct. 2019; Akihide Koguchi leg.; Eleutherococcus divaricatus (twig galls, flower galls); HIC, NCHU, dry, slide mounted and in ethanol .

Note. The redescription below is based on material examined from Japan and South Korea, as well as the description in Loginova (1967) of eastern Russia material and notes on Chinese specimens by Li (2011).Measurements given below are taken from the material from Japan and South Korean, with measurements, if different and where reported in Loginova (1967), shown in [].

Description. Adult ( Figs 4A–B , 5 , 6 ). Coloration. General body color brown ( Japan and South Korean), or yellow-orange with parts brown (eastern Russia; Loginova 1967). Antennae with apical half of 1 st segment and the remaining antenna dark brown ( Japan and South Korean), or only terminal segment dark (eastern Russia; Loginova 1967). Compound eyes dark brown. Ocelli orange. Legs brown. Forewing veins brown, membrane transparent, with a small dark spot at trifurcation of R+M+Cu 1 in Japanese and South Korean material, but possibly absent in eastern Russia material or omitted from Loginova’s (1967) description.

Structure. Body large-sized, length from anterior head margin to tip of folded forewing 5.3–5.8 mm [ 4.6–5.7 mm], female generally larger; covered in short fine setae. Head ( Fig. 5A ) slightly narrower than thorax. Vertex width 1.4–1.5 x [1.6 x] length, minutely pubescent. Genal processes prominent, length along mid-line 0.8–1.0 x vertex length, divergent, conical, subacute at apex, with long pubescence. Antenna ( Fig. 5B ) length 2.0–2.1 x [1.9–2.0 x] head width, antennal segment 3 approximately 1.4 x segment 4, relative length of flagellar segments as 1.0: 0.7: 0.3: 0.4: 0.3: 0.3: 0.2: 0.2; two unequal terminal setae: longer seta 1.1 x, and short, truncate seta 0.2 x segment 10 length. Thorax weakly arched dorsally, minutely pubescent. Hind leg ( Fig. 5E ) metatibia length 1.2–1.3 x head width. Forewing ( Fig. 5C ) relatively long and narrow, length 6.0–6.6 x head width, and 2.8–2.9 x width, widest in the middle; wing apex acute; vein Rs moderately long, gradually curved to fore margin; vein M evenly curved with bifurcation posterior to line connecting apices of veins Rs and Cu 1a; cell m 1 larger than cell cu 1; vein Cu 1a evenly curved, vein Cu 1b straight; veins minutely pubescent. Hindwing ( Fig. 5D ) 0.65 x as long and 0.5 x as wide as forewing.

Male terminalia ( Fig. 6A–C ). Proctiger short, with moderate posterior lobes reaching maximum extension in the basal half, covered in long setae except for basal third laterally ( Fig. 6A ). Subgenital plate subglobular, with medium long setae laterally and ventrally; posterior dorsal margin slightly convex. Paramere ( Fig. 6B ) about as long as proctiger; in profile more or less parallel sided and straight, slightly sinuous, irregularly narrowing to apex which is acute and directed inward and rearward; inner face beset with long setae, outer surface with shorter setae. Distal aedeagus segment ( Fig.6C ) slightly shorter than paramere ( Figs6A , 16 ),curved medially with semi-circle projections, apical portion inflated, crescent-shaped, with acute apex [eastern Russian specimens have distal aedeagus segment slightly longer, less curved medially and the semi-circular projections are less extended]; sclerotized end tube of ductus ejaculatorius short, sinuous. Female terminalia ( Fig. 6D ) cuneate, slender; proctiger abruptly narrowing in apical fourth with acute apex, dorsal margin more or less straight, slightly longer than subgenital plate, with long setae in the apical half, anal ring length approximately one fourth proctiger length, consisting of a single row of pores. Subgenital plate, in profile, triangular, apex acute, beset with medium long hairs laterally and ventrally. Ovipositor dorsal valvulae cuneate, ventral valvulae straight with a single shallow serration.

Fifth instar immature [based on specimens from Japan] ( Fig. 7 ). Coloration. General color brown. Forewing pad and thorax pale brown. Body ( Fig. 7A ) length 1.3–1.4 x width. Body surface, including margin of head, wing pads ( Fig. 7C ), caudal plate and legs covered with medium dense, narrow truncate sectasetae. Antenna ( Fig. 7E ) relative length of antennal segments 3 to 8 as 1.0: 0.5: 0.5: 0.4: 0.6: 1.4. Legs ( Fig. 7B ) as for generic description. Forewing pad length 2.9 x width, and 2.6 x antenna length. Caudal plate length 0.7 x width. Circumanal ring ( Fig. 7D ) heart-shaped (medial constriction mainly from anterior); width 0.3 x caudal plate width; outer ring mostly composed of a single row of elongate pores with a few intermittent irregular pore shapes; inner ring composed of a mixture of short and elongate pores.

Host plant. Eleutherococcus sessiliflorus in Russia ( Loginova 1967) and South Korea ( Cho et al. 2017), Eleutherococcus divaricatus in Japan (this study), and Eleutherococcus senticosus in China ( Li 2011) and South Korea (according to Kwon & Kwon 2020).

Biology. Induces round galls on the leaf surface in South Korea (illustrated in Cho et al. 2017; Kwon & Kwon 2020), but in Japan produces rounded galls, sometimes at high densities, on twigs, stems and leaf petioles, as well as on male and female flowers ( Fig. 4C–D ). In Japan, it appears to be bivoltine, with the first generation adults emerging in early summer (June–July) and the second generation around October (A. Koguchi, personal communication).

Distribution. China ( Li 2011), Eastern Russia ( Loginova 1967) and South Korea ( Cho et al. 2017, Kwon & Kwon 2020), and reported here for the first time for Japan.

Comment. Specimens examined from Japan and South Korea conform closely to the original description and illustrations by Loginova (1967) based on material from eastern Russia. Loginova (1967) reports a slightly smaller body size ( 4.6–5.7 mm) compared to the Japanese and Korean material ( 5.3–5.8 mm), and a forewing shape that is slightly longer and narrower, with the relative size difference between cells cu 1 and m 1 more marked; Loginova (1967) also does not mention a dark spot at trifurcation of R+M+Cu, although this may simply be omitted from her description. We also note that specimens from South Korea are marginally larger than Japanese material. Altogether, the differences equate to moderate natural variation across the species range. Kwon & Kwon (2020) list this species as a pest on medicinal Eleutherococcus spp. in South Korea.

Genetic resources. Adult and immature sequences of COI were identical, unique haplotype: PQ817986.

Figures

FIGURE 4. Triozidus stackelbergi adults and galls on Eleutherococcus divaricatus. A, male; B, female; C, twig and male flower galls on E. divaricatus; D, detail of male flower galls.

FIGURE 5. Adult Triozidus stackelbergi comb. nov. A, head; B, antenna; C, forewing, with small dark spot at trifurcation of R+M+Cu (arrowed); D, hindwing; E, hind leg. Scale bars: 0.1 mm (A, B, E); 1 mm (C, D).

FIGURE 6. Terminalia of Triozidus stackelbergi comb. nov. A, male terminalia (lateral view); B, paramere (inner surface); C, distal portion of aedeagus showing medial semicircular projections (arrowed); D, female terminalia (lateral view). Scale bars: 0.1 mm.

FIGURE 7. Fifth instar immature of Triozidus stackelbergi comb. nov. A, habitus; B, tarsal arolium showing asymmetric development of tarsal claws (vestigial claw arrowed); C, forewing pad marginal sectasetae; D, circumanal ring showing regular single row of pores (inset); E, antenna. Scale bars: 0.1 mm.

FIGURE 16. Phylogenetic placement of Triozidus in family Triozidae is indicated by a black square representing a subgroup within Group B (see Percy et al. 2018), the related genera are expanded on in the text. An asterix indicates the placement of the type species of Heterotrioza, H. chenopodii in Group D, and Trioza, T. urticae in Group M, and Dyspersa sensu Cho et al. (2022) in Group A. Configuration of the three Triozidus taxa to one another based on the 714 bp COI fragment data (unique haplotypes only) is shown, with T. burckhardti placement indicated based on the backbone analysis (see text); taxon placements within Triozidus are uncertain in both analyses due to short internal branches and low to moderate bootstrap support, with a slightly different taxon configuration recovered in the ML backbone constraint analysis (see text). Illustrations of forewing, paramere and aedeagus are shown for all six Triozidus species to indicate comparative sizes; an asterisk by T. ceratophorus and T. eleutherococci indicates the illustrations are redrawn with reference to Li (2011) and Konovalova (1980, 1988) respectively, and in these cases paramere and aedeagus may not be to scale, plus the apex of the aedeagus is partly obscured in the illustration for T. eleutherococci. The annotation of the mitogenome of T. yangorum is graphically represented at top right.