Itoigawacoris venustulus, Yasunaga & Mashima, 2025

Yasunaga, Tomohide & Mashima, Gō, 2025, A new genus and species of mirine plant bug endemic to central Honshu, Japan, a region receiving the world’s heaviest snowfall (Insecta: Hemiptera: Heteroptera: Miridae: Mirinae: Mirini), Zootaxa 5716 (3), pp. 397-408 : 399-406

Itoigawacoris venustulus sp. nov.

Figs. 1–2 , 3A–E , 4A–I , 5A–J , 6A–I , 7

Diagnosis. Recognized readily by its unique color pattern and body shape ( Fig. 1A–B ) and characters provided in above generic diagnosis. At first sight similar in general appearance to Pinalitus nigriceps (Kerzhner, 1988) , from which this new species is easily distinguished by the white antennomere III and cuneus. All East Asian Pinalitus members are specialists of Pinaceae conifers ( Kerzhner 1988b, Yasunaga 1994, 2001). The nymphs are primarily recognized by the entirely scarlet general coloration ( Figs. 1G , 2C–F ), and the 4–5th instar immatures have unique microstructures ( Fig. 6B–C, E–F ).

Description. Head shiny fuscous; buccula narrowly whitish. Antenna dark brown; segment I reddish brown, with more or less darkened apex; segment II almost linear, not thickened towards apex; segment III milky white; segment IV dark grayish brown. Labium shiny chocolate brown, about as long as width across hemelytra; segments II, III and base of IV pale reddish brown. Pronotum fuscous, shining, with pale reddish brown collar; mesoscutum and scutellum shiny fuscous; scutellum with pale apex; propleuron shiny fuscous as in pronotum; other parts of pleurites dark reddish brown; metathoracic scent efferent system pale reddish brown, with darkened anterior margin. Hemelytron brown to dark brown, sometimes partly or widely tinged with red; lateral margin of exocorium (embolium) with a dark, narrow stripe continuing to cuneal margin; cuneus creamy white, narrowly darkened laterally and apically; membrane including veins and areolar cells smoky brown, with a whitish fascia mesally. All coxae whitish brown, partly or widely tinged with orange; all femora orange-scarlet; apices of pro- and mesofemora each with two pale rings; metafemur with two obscure rings; tibia whitish brown; each tarsomere III infuscate. Abdomen shiny orange-brown; ventral surface with a pair of brown fasciae laterally along rows of spiracles; male genital segment (pygophore) dark brown. Male and female genitalia as mentioned in generic description.

Measurements. See Table 1.

Etymology. From Latin, venustus (lovely, beautiful, elegant) with a diminutive suffix (-ulus), referring to its neat general appearance of this new species; the Latin word venustus is also derived from Venus, and the type locality, Mt. ‘Myojo’, means the Venus (planet, also implies Hesperus and Lucifer) in traditional Japanese.

Distribution. Japan (central Honshu, Niigata Prefecture).

Biology. Continuing fieldwork performed by the second author (G. Mashima) in 2024 and 2025 successfully confirmed the life history and breeding host. This mirid is monophagous, associated only with a Japanese boxwood, Buxus microphylla Sieb. & Zucc. ( Buxaceae ) ( Fig. 2B ), on which the immature forms and adults were observed to co-occur. The mirid undoubtedly has a univoltine life cycle and overwinters in the egg stage. The early instar nymphs appear on the host leaves in middle May ( Fig. 2C–D ), when patches of snow remain around the boxwoods ( Fig. 2A–B ). The newly emerged adults are found from late May to early June, and the annual generation is presumed to be completed until early August.

Under rearing conditions, both mature and late immature forms were observed to suck on an artificial diet (diluted fermented milk beverage, Fig. 2G , cf. Miyazaki et al. 2020) and scavenge on cadavers of other individuals ( Fig. 2E ). This mirid appears to have in some part of a zoophagous food habit.

Material examined. Holotype ( ♂), JAPAN: Central Honshu, Niigata Pref., Itoigawa City, Kotaki , Mt. Myojo , N36.936828 E137.817457 ( 577 m alt.), on Buxus microphylla , 7 Jun 2025, G. Mashima leg. ( NWHS) ( AMNH _ PBI 00380778 ) . Paratypes. JAPAN: Niigata Pref., Itoigawa City, Kotaki, Mt. Myojo , N36.936135, E137.818899 ( 524 m alt.)— N36.941822, E137.818292 ( 1184 m alt.), on Buxus microphylla , 7 Jun 2025, G. Mashima, 21 ♂, 17 ♀ (several specimens were reared from 4–5th instar immatures) ( AMNH, SNU, TYCN) ; same data as for holotype, except for date 28 May 2025, 1 ♂, 1 ♀ (final instar nymphs when collected and emerged on 7–8 Jun) ( TYCN) ; same locality, N36.9343, E137.8200 ( 520 m alt.)— N36.9379, E 137.8162 ( 610 m alt.), 15 Jul 2024, 1 ♂, 3 ♀ ( TYCN) ; same data except for date 22 Jul 2024, 3 ♂, 8 ♀ ( TUAK, TYCN) ; same data except for date 5 Jul 2024, 3 ♂, 3 ♀ ( GMCN) . Some additional specimens (damaged during molt to adults) were also collected from Mt. Kurohime ( 5 km NNW of Mt. Myojo, 36°58’ N 137°47’ E, Fig. 7 ) on 29 May 2025 ( SNU, preserved in 95% EtOH) .

Figures

FIGURE 1. Habitus images of living individuals of Itoigawacoris venustulus. A, B (right), C, F. Male adults. B (left), D, E. Female adults. G. Final (5th) instar nymph (approaching eclosion, with darkened head, antennomeres and wing-pads). A–B, G. Dorsal view. C–D. Left lateral view. E. Frontal view. F. Ventral view. B (left): small-sized female; C: grooming left antenna.

FIGURE 2. Habitat with confirmed breeding host (A–B), immature forms at natural habitat (C–F) and reared adult individuals (G–H) of Itoigawacoris venustulus. A. Sampling site, Mt. Myojo with the remaining snow (577 m alt., 28 May 2025). B. Same (524 m alt.). C. Second instar immature form. D. Third instar. E–F. Fourth instar. G. Teneral female sucking on artificial diet (diluted milk-based beverage). F. Female adult scavenging on cadaver of other female individual in acrylic cage.

FIGURE 3. Male (A–B, F, H) and female (C–E, G, I) genitalia of Itoigawacoris venustulus (A–E) and its superficially similar taxa, Pinalitus rubeolus (Kulik, 1965) from Gyeonggi-do, Korea (F), Pinalitus nigriceps (Kerzhner, 1988) from Niigata, Japan (G) and Pinalitopsis rhodopotnia Yasunaga, Schwartz & Chérot, 2002, paratype from Kochi, Japan (H–I). A. Genital segment (pygophore), dorsal view. B, F, H.Vesica. C. Genital chamber. D. Ovipositor (gonapophysis I). E. Posterior wall. G, I. Sclerotized ring (right).

FIGURE 4. Scanning electron micrographs for Itoigawacoris venustulus (A−I), Pinalitopsis rhodopotnia Yasunaga, Schwartz & Chérot, 2002 (J−M) and Pinalitus nigriceps (Kerzhner, 1988) (N−P).A–B, J, N. Anterior body. C–D. Head and pronotum. E. Vestiture pattern on scutellum and anterior hemelytron. F, K, O. Metathoracic scent efferent system (left). G, M, P. metatarsus. C, J, Anterior body, left lateral view. H–I, L. Pretarsal structure of metaleg.

FIGURE 5. Scanning electron micrographs of male (A–F, O) and female (G–N) genitalia for Itoigawacoris venustulus (A–J), Pinalitus nigriceps (Kerzhner) (K–L) and Pinalitopsis rhodopotnia Yasunaga, Schwartz & Chérot, paratypes (M–O).A. Genital segment (pygophore), dorsal view. B. Same, left lateral view. C. Left paramere. D. Right paramere. E. Vesica, caudal view. F. Same, frontal view. G, K, M. Sclerotized ring and adjacent structures on genital chamber. H–J, L, N. Posterior wall.

FIGURE 6. Scanning electron micrographs for 4th (A–C) and 5th (D–I) instar nymphs of Itoigawacoris venustulus, and Lygocoris idoneus (Linnavuori, 1963) (J–O). A, D. Dorsal habitus. B, E. Head. C, F. Unknown microstructures on vertexfrons. G. Compound eye. H. Scent efferent system on abdominal terga. I. Metatarsus. J. Anterior body. K. Pretarsal structure of metaleg. L. Male genital segment (pygophore). M. Vesica. N. Female genital chamber. O. Posterior wall.

FIGURE 7. Map showing the type locality of Itoigawacoris venustulus.