Triozidus Li, 1994

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 : 115-117

Genus Triozidus Li, 1994 stat. rev.

Triozidus Li, 1994 . Type species: Triozidus acanthopanaicis Li, 1994: 85 , by original designation.

Lunatrioza Kwon, Suh & Kwon, 2022. Type-species: Trioza stackelbergi Loginova, 1967: 345 , by original designation; nomen nudum [conference poster, not a published work in the sense of the International Code of Zoological Nomenclature], syn. nov.

Adult colour and structure. General body colour yellow-brown to dark brown, with light to mid-brown on areas of dorsum and legs, and darker brown to black on some or all of antennal flagellum, head and pronotum, and abdominal tergites. Forewing membrane clear or yellowish, with or without distinct dark patch around clavus. Medium to large bodied, 3.5–6.0 mm (including wings). Head narrower to slightly wider than thorax, inclined at about 45–50º from longitudinal body axis (in lateral view). Head with well developed, medium-long genal processes, vertex trapezoidal, moderately concave medially at posterior margin, lateral ocelli on small tubercles, medial epicranial suture distinct. Clypeus narrowly rounded ventrally, distal proboscis segment short.Antennae medium long, slender, 10-segmented, segment 3 longest, a single rhinarium subapically on segments 4, 6, 8 and 9. Thorax weakly to moderately arched. Pronotum deflexed from mesothorax at a 45° angle. Legs moderately short and robust, tibia longer than femur; hind leg with meracanthus well developed, horn-shaped, more or less straight, acute at apex; metatibia length equal to or longer than head width, with a single or cluster of small spines basally, inflated apically and bearing 3 (1+2) sclerotized apical spurs (not stalked) and a row of unsclerotized bristles; metabasitarsus without apical spurs, slightly longer than apical metatarsus. Forewing relatively large, length approximately 1.2–1.5 x body length, broadest in the middle or distal to the middle, with trifurcation of veins R+M+Cu strict; membrane lacking surface spinules except occasional small area with spinules at base of cell cu 2, a narrow cluster of marginal radular spines present at wing margin, more or less centrally positioned in cells m 2 and cu 1, and in the posterior half of cell m 1; size of cell m 1 subequal to, or notably larger than, cell cu 1; vein Rs either long and sinuous or medium short and evenly curving to fore margin; forewing apex subacute to acute. Hindwing medium-short, length less than 2/3 forewing length. Male terminalia with subgenital plate globose, posterior margin more or less rounded or more angular (in lateral view); proctiger short with slight to moderate posterior lobe medially, length subequal or shorter than paramere; paramere simple (in lateral profile), more or less parallel sided, either straight, moderately sinuous or with incision medially on anterior surface, tapering to blunt or pointed apex; distal aedeagus segment either distinctly angled or arched with a bipartite projection medially consisting of either thumb-like or semicircular projections, or less typically more or less straight and lacking such projections, apex inflated and developed into a shallow or widely curving hook. Female terminalia short, length approximately subequal to head width, proctiger slightly longer than subgenital plate, anal ring large and consisting of a single row of pores. Ovipositor dorsal valvulae relatively small and cuneate, ventral valvulae with one or a few shallow serrations.

Immature colour and structure. Fifth instar immature. Coloration. General body colour yellowish-brown to dark brown, with light to mid-brown areas on dorsum and legs, and darker brown to black on some sclerites and terminal antennal segments. Body shape in dorsal view elongate-oval with wing pads protruding and humeral lobes developed; sclerites present dorsally and ventrally. Body surface covered with medium dense simple setae or sectasetae. Antenna weakly curved, 8-segmented; scape, pedicel and segment 3 thicker than remaining flagellum; with a single subapical rhinarium on each of segments 4 and 6, and two on segment 8. Legs moderately long, femur shorter than tibiotarsus; tarsi with only one fully developed claw (outer), tarsal arolium longer than claws, triangular with a medial cleft, with short unguitractor, lacking pedicel. Humeral lobe of forewing pad relatively short, reaching hind margin of eye. Caudal plate broadly rounded posteriorly. Circumanal ring in ventral position, relatively wide and short; outer ring mostly composed of a single row of elongate pores, or with convolutions and intermittent multi-pore sections.

Egg. Only known for T. stackelbergi . Oblong-ovoid with a short, laterally positioned pedicel sub-basally on underside and short tail (illustrated in Loginova 1967).

Host plant. Eleutherococcus spp. ( Araliaceae ).

Biology. All species for which biology is known produce enclosed galls on some or all of the following host organs: leaves, twigs, male and female flowers, petioles or petiolules.

Distribution. The genus occurs in China ( Li 2011), Japan ( Shinji 1940, Miyatake 1996), Russia ( Loginova 1967, Konovalova 1988), South Korea ( Cho et al. 2017, Kwon & Kwon 2020), and Taiwan (this study).

Comment. The genus includes four described nominal species and two new species. Kwon & Kwon (2020) synonymised Triozidus acanthopanaicis Li, 1994 , the type species of Triozidus , with Heterotrioza stackelbergi . Species of Triozidus sensu novo have been variously referred to Heterotrioza Dobreanu & Manolache , Heterotrioza ( Dyspersa) Klimaszewski , Trioza or Triozidus ( Klimaszewski 1973; Li 2011; Kwon & Kwon 2020; Cho et al. 2022). Loginova (1967) discussed morphological differences between T. ukogi and T. stackelbergi , and Cho et al. (2017) pointed out that the latter has been misidentified repeatedly in the literature from Korea as either Trioza ukogi , Heterotrioza ( Dyspersa) ukogi or Heterotrioza ukogi .

Unusual features of the genus typically, but not exclusively, include the bipartite projection on the shaft of the apical aedeagus segment (i.e., not on the apex as in Heterotrioza ), and the immatures with uneven or asymmetrical development of tarsal claws; interestingly, it seems that the undeveloped claw becomes increasingly vestigial in later instars. Many triozid groups are known to be relatively morphologically homogeneous resulting in peripatetic taxonomic histories, and this is especially the case with taxa formerly placed within the catch-all genus Trioza . These challenges have increased the reliance on molecular data, and the reciprocal illumination these data offer, to help resolve morphologically challenging groups. Nevertheless, Triozidus has a number of morphological characters that collectively serve to help distinguish it from related groups. In particular, the large size of the forewing relative to body size is more exaggerated than in related genera (e.g., Dyspersa , Heterotrioza , Lauritrioza Conci & Tamanini ,

Trioza s.s.), the forewing cell m 1 is always larger than cu 1 (usually markedly so), the transition from vertex to genal cones is not as distinctly stepped, and the apex of the metatibia is more expanded. These, together with the biology and host plants in Eleutherococcus , and the immature vestigial claw, define Triozidus . Relationships with other

Trioza sensu lato taxa and other genera in Group B (as shown in Fig. 16 ), are still in flux taxonomically as these groups become more well defined, but the same assemblage of characters given above, together with the molecular data, provides the best diagnosis.

Figures

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.