Triozidus burckhardti Liao & Percy, 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 : 118

Triozidus burckhardti Liao & Percy sp. nov.

( Figs 1A–B , 2 , 3 )

Type material. Holotype: TAIWAN • ♂; Pingtung Co., Manzhou, Changle ; 22°04’53.9”N, 120°50’09.5”E; 29 Jan 2024; Y. C. Liao leg.; Eleutherococcus trifoliatus ; NCHU, dry mounted . Paratypes: TAIWAN • 1♂, 1♀; same data as for holotype, but in ethanol and slide mounted . 1♂, 2♀; same data as for holotype, but DMPC, in ethanol . 1♂, 1♀; same data as for holotype, but NHMB, in ethanol . 3♀; same data as for holotype, but 26 Mar 2020 .

Description. Adult ( Figs 1A , 2 , 3 ). Coloration. Body color yellowish brown with entire head, compound eyes and antennae black ( Fig. 1A ). Abdominal tergites blackish brown. Legs yellow. Forewing pale yellow, transparent, slightly darker brown around clavus ( Fig. 2E ). Hindwing transparent.

Structure. Body median-sized, length from anterior head margin to tip of folded forewing 3.6–3.8 mm, female generally larger. Head ( Fig. 2A ) slightly narrower than thorax. Vertex width 1.7–1.8 x length, minutely pubescent. Genal processes prominent, length along mid-line 0.7–0.8 x vertex length, divergent, conical, acute at apex, covered in short hair. Antenna ( Fig. 2B ) length 1.8–2.0 x head width, antennal segment 3 approximately double length of segment 4, relative length of flagellar segments as 1.0: 0.5: 0.3: 0.4: 0.3: 0.3: 0.2: 0.2; two unequal terminal setae: longer seta 0.7 x, and shorter seta 0.3 x segment 10 length. Thorax moderately arched dorsally, minutely pubescent. Hind leg ( Fig. 2C ) metatibia length 1.0–1.1 x head width. Forewing moderately broad ( Fig. 2E ), length 5.8–5.9 x head width, and 2.9–3.0 x width, widest slightly distal to 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 Cu1 a; cell m 1 larger than cell cu 1; vein Cu 1a evenly curved, vein Cu 1b straight; veins minutely pubescent. Hindwing ( Fig. 2D ) 0.6 x as long and 0.5 x as wide as forewing.

Male terminalia ( Figs 3A–C ). Proctiger short, with moderate posterior lobes reaching maximum extension in the basal half ( Fig. 3A ). Subgenital plate subglobular, with medium long setae laterally and ventrally; posterior dorsal margin slightly convex. Paramere ( Fig. 3B ) slightly longer than proctiger; in profile angulate at base, with a deep incision anteriorly in the basal half, before narrowing to apex which is acute and directed inward; inner face and surface beset with median-long setae. Distal aedeagus segment ( Fig. 3C ) about as long as paramere ( Figs 3A , 16 ), straight medially without projection, apical portion largely inflated into a hook with acute apex; sclerotized end tube of ductus ejaculatorius short, slightly sinuous. Female terminalia ( Fig. 3D ) cuneate, short; proctiger dorsal margin slightly sinuate with medial depression and acute apex, only slightly longer than subgenital plate, with long setae in the apical half, anal ring length approximately one third proctiger length, consisting of a single row of pores. Subgenital plate, in profile, triangular, apex acute, beset with long hairs laterally and ventrally. Ovipositor dorsal valvulae cuneate, ventral valvulae straight with several shallow serrations apically.

Measurements in mm ( 1 male, 1 female). Body length (including forewing) ♂ 3.56; ♀ 3.75. Head width ♂ 0.47; ♀ 0.52. Vertex width ♂ 0.27; ♀ 0.31. Vertex length ♂ 0.16; ♀ 0.17. Genal cone length ♂ 0.11; ♀ 0.13. Antenna length ♂ 0.93; ♀ 0.93. Metatibia length ♂ 0.50; ♀ 0.53. Forewing length ♂ 2.75; ♀ 3.0. Forewing width ♂ 0.93; ♀ 1.05. Aedeagus length ♂ 0.20. Paramere length ♂ 0.22. Proctiger length ♀ 0.62. Subgenital plate length ♀ 0.60.

Etymology. The specific name honours Dr Daniel Burckhardt for his contribution to our knowledge of the world’s psyllid fauna.

Distribution. Taiwan; only found in the southernmost part (Hengchun peninsula).

Host plant. Probably Eleutherococcus trifoliatus ( Araliaceae ), but immature specimens are needed to confirm host and gall type.

Biology. This species apparently shares the same host plant as T. yangorum but the two psyllid species are allopatric, with T. burckhardti only found in the southernmost part of Taiwan and T. yangorum in central and northern Taiwan. They also appear to have a similar galling biology, galls and immatures were recorded for T. burckhardti but no immature specimens were preserved. Immatures (1 st instar) were observed to develop within fully enclosed round galls that are positioned on the base of leaflets, or just below the leaflets on the petiolules, or on the leaf petioles. Each gall consists of a single gall chamber with usually a single immature. Galls are found individually or in aggregates of two to four galls per leaf, often with a gall on each of the three petiolules ( Fig. 1B ). As is the case for T. yangorum , T. burckhardti is univoltine with adults emerging in January.

Genetic resources. Adult male and female sequences of COI and cytB were identical, unique haplotypes: PQ817990 and PQ817253 (for COI and cytB respectively).

Figures

FIGURE 1. Triozidus burckhardti sp. nov. and Triozidus yangorum sp. nov. adults, immature and galls on the host plant, Eleutherococcus trifoliatus. A, T. burckhardti female; B, closed galls of cf. T. burckhardti with a single gall on each petiolule of the trifoliate leaf; C, T. yangorum male; D, T. yangorum fifth instar immature within gall chamber; E, close up showing three petiolule galls of T. yangorum on a single leaf, the upper already opened; F, the scandent host, E. trifoliatus, showing distribution of petiolule galls.

FIGURE 2. Adult Triozidus burckhardti sp. nov. A, head; B, antenna; C, hind leg; D, hindwing; E, forewing. Scale bars: 0.1 mm (A, B, D); 1 mm (C, E).

FIGURE 3. Terminalia of Triozidus burckhardti sp. nov. A, male terminalia (lateral view); B, paramere (inner surface); C, distal segment of aedeagus; D, female terminalia (lateral view). 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.