Neolygus autumnus, Yasunaga, 2024

Yasunaga, Tomohide, 2024, New species of the plant bug genus Neolygus Knight from Japan, Taiwan and Thailand (Hemiptera: Heteroptera: Miridae: Mirini), Zootaxa 5446 (4), pp. 451-487 : 454-462

Neolygus autumnus n. sp.

Figs. 1A–B , 4A–C , 6A–F , 13A–I , 14A–F

Material examined. Holotype (♂). JAPAN: Kyushu, Miyazaki Pref., Takachiho Town, Gokasho-Kogen , Mt. Sobosan , 32.81, 131.27, 21 Sep 1994, S. Ide ( NWHS) ( AMNH _ PBI 00378765 ) . Paratypes: JAPAN: Honshu : Kyoto Pref., Fukuchiyama City, Ooe Town, Senjogadake , Mt. Ooeyama , 35.46, 135.12, Hydrangea paniculata , 17 Sep 1984, M. Tomokuni ( NSMT) . Kyushu : same data as for holotype, 2♂ ( TYCN) ; Fukuoka Pref., Soeda Town, Mt. Hikosan , 33.4820, 130.9089, 27 Aug 1935, T. Esaki, 1♀ ( KUEC) ; Kumamoto Pref., Izumi Village [= current Yatsushiro City, Izumi Town], Mt. Hakucho ( Shiratori ), 1200–1300 m alt., 32.480, 131.005, on flowers of Hydrangea paniculata , 6–7 Aug 1988, T. Yasunaga, 3♂ 2♀ ( TYCN) ; same data, except for date 1 Aug 2003, 2♂ 3♀ ( TYCN) ; Oita Pref., Takeda City, Mts. Kuju, Daisen-rindo (trail), 33.11, 131.26, on flowers of Hydrangea paniculata , 1 Aug 1988, Y. Abe, 3♂ 2♀ ( TYCN) . Shikoku : Ehime / Kochi Pref., Jiyoshi Pass , 900–1000 m alt. 33.4720, 132.9399, 6 Aug 1993, T. Yasunaga, 1♀ ( TYCN) ; Ehime / Kochi Pref., Onogahara , 33.473, 132.885, 5 Aug 1993, T. Yasunaga, 1♂ ( TYCN) ; Kochi Pref., Hongawa Village [= current ‘Ino Township’], Teragawa , 33.756, 133.168, 24 Jul 1996, T. Yasunaga, 1♂ 1♀ ( TYCN) .

Diagnosis. Based on similar color pattern, genitalic structures and host association, this new species is most closely related to N. honshuensis (Linnavuori) , from which N. autumnus n. sp. can be distinguished by the following characters: Smaller size and shorter appendages ( Table 1 ); basic coloration relatively milky pale green in fresh specimens ( Fig. 1A–B ); labium longer than metafemur; smaller peritreme on scent efferent system ( Fig. 13D ); apical protuberances of both parameres weaker ( Figs. 6A–D , 13N–O ); vesical spiculum shorter, less curved apically and ventral sclerite narrower ( Figs. 6E , 14A, D ); posterior wall with narrower lateral lobe and spinules on interramal sclerite rather sparsely distributed ( Fig. 14B, E ).

Description. Body oval, rather small in size ( Figs. 1A , 4A–B ); dorsum pale green, tinged with milky white in fresh specimens ( Fig. 1A ), with uniformly distributed, pale, simple, reclining setae ( Fig. 13A–B ); general coloration fading to brownish in dry-preserved specimens ( Fig. 4B–C ). Head shining; vertex relatively narrow, with distinct basal transverse carina that is thicker than pronotal collar ( Fig. 13A ); apex of clypeus always fuscous ( Fig. 1B ). Antenna pale brown, in fresh specimens tinged with red; segments III and IV darker. Labium shiny pale brown, rather long, reaching or slightly exceeding apex of metacoxa ( Fig. 4C ). Pronotum immaculate; scent efferent system creamy yellow, with narrow peritreme ( Fig. 13D ); mesoscutum widely darkened. Hemelytral dark macula variable; clavus sometimes widely darkened ( Fig. 1A , 4A ); dark macula on apical part of corium usually small ( Fig. 4A–B ) but widened in some specimens ( Fig. 1A ); membrane pale smoky brown, with pale veins. All coxae and legs pale; apical part of metafemur usually with two brown rings; apex of each tarsomere III darkened; meta-tarsomere II slightly longer than III ( Fig. 13E ); pretarsal structure as in Fig. 13F . Ventral side of abdomen uniformly pale.

Male genitalia ( Figs. 6A–E , 13G–I , 14A, D ): Parameres with rather small apical protuberances ( Fig. 6A–D ); right paramere with rather short, sharply pointed hypophysis ( Fig. 6B, D ); vesica with spiculum weakly curved apically and ventral sclerite rather narrow ( Figs. 6E , 14A, D ).

Female genitalia ( Figs. 6F , 14B–C, E–F ): Sclerotized rings thick-rimmed, elongate, mesially contiguous to each other ( Fig. 6F ); posterior wall as in Fig. 14B, E ; spinules on interramal sclerite rather sparsely distributed and restricted anteriad; lateral lobe rather narrow.

Measurements: See Table 1 .

Etymology. From Latin adjective, autumnus [= autumn], referring to emergence of this new species mainly from late summer to early autumn.

Distribution. Japan (SW. Honshu, Shikoku and Kyushu).

Biology. The breeding host was confirmed as Hydrangea paniculata Sieb. ( Hydrangeaceae ), on which teneral adults and late instar immature forms were observed. This new species ( Fig. 1A–B ) and N. honshuensis (Linnavuori) ( Fig. 1C–D ) were sometimes collected at same sites in southern Japan, but N. autumnus n. sp. (from late July to early October) emerges later than N. honshuensis (from mid-June to mid-August).

Remarks. Because of great similarity in external appearance, the present new species has in the past been regarded as a small variant or 2nd generation of its sibling, N. honshuensis (e.g. Yasunaga 1991b, 2001). However, subsequent observations revealed that the adults of both species coexisted in August. In addition, N. autumnus n. sp. is separable from N. honshuensis by the characters mentioned in above diagnosis. Speciation pattern of these sibling species may be derived from seasonal (allochronic) segregation.

The Japanese fauna of Neolygus is now revealed to include 39 valid species.As discussed above, several species are known only by the males (for most of the species, female specimens in all likelihood available but yet to be determined). Therefore, a definitive key to species is currently under construction and exact identification of many congeners is relied only upon observation of the male parameres and vesica (illustrations available in Kerzhner 1988; Yasunaga 1991a, b, 1992, 1999, 2001, 2023; Yasunaga & Schwartz 2005; Yamamoto & Yasunaga 2020; Noguchi et al. 2023).

As a key to Japanese species provided by Yasunaga (1992) is no longer usable, however, I herein suggest the following key that would aid in identification of species or approximate grouping. The present key is constructed principally for male specimens (species shown in couplets 1–4 applicable to both sexes). For unequivocal identification of the species appearing in couplets 19–24, observation (or dissection) of the genitalia is required († species currently represented only by male): † N. angustivertex (for figures of male genitalia, cf. Yasunaga 2023), † N. chichibumontis n. sp. ( Fig. 7A–D ), N. flavoviridis (cf. Yasunaga 1991c), N. hoberlandti ( Yasunaga 1991b, 2023), † N. kawasawai (Yasunaga 2023) , N. makiharai ( Yasunaga 1992) , † N. nozakii ( Fig. 7E–F ; Yasunaga 2023), † N. tomokunii ( Yasunaga 1991c) and N. lobatus (immaculate variant, Fig. 3D ; Yasunaga 1991b).

1. Dorsum widely fuscous, reddish or yellow-orange, lacking greenish tinge......................................... 2

- Basic coloration on dorsum greenish (or fading to pale brown in dry-preserved specimens)........................... 4

2. Body ovoid; hemelytron widely orange-scarlet with dark maculae posteriad................................. N. roseus

- Body elongate ovoid; hemelytron almost uniformly fuscous (only cuneus sometimes reddish)......................... 3

3. Antennomeres I and II dark brown; femora usually dark brown, without reddish tinge......................... N. ryoma

- Antennomeres I and II pale brown; femora red or orange-brown...................................... N. miyamotoi

4. Antennomere I usually fuscous; vernal species restricted to a hackberry, Celtis sinensis ....................... N. tosanus

- Antennal segment I always pale brown (pale green or yellowish green in fresh specimens)........................... 5

5. Male antennomere III as long as or longer than basal width of pronotum; male metatibia> 4 mm [if male antennomere III long enough, then metatibia <3.8 mm (= N. nakatanii , part)]....................................................... 6

- Male antennomere III obviously shorter than basal width of pronotum; male metatibia <3.8 mm ...................... 7

6. Body elongate, slender, subparallel-sided; base of antennomere II with a dark annulation ( Fig. 3M ); labium longer, surpassing apex of mesocoxa; pronotal disk and apical part of corium with dark maculae or spots; associated mainly with alders, Alnus spp. ( Betulaceae ).............................................................................. N. longiusculus

- Body elongate oval; basal part of antennomere II pale brown, not darkened; labium shorter, not exceeding apex of mesocoxa; pronotum and corium almost immaculate (apex of corium narrowly or faintly darkened); restricted to Araliaceae broadleaf trees, Chengiopanax sciadophylloides and Eleutherococcus senticosus ................................. N. majusculus

7. Smallest species in Japan, with body length 3.9–4.3 mm [color pattern variable ( Fig. 3E–F ); if body length <4.5 mm and dorsum uniformly pale, then antennomere II shorter than labium = N. makiharai (part)]...................... N. pteleinus

- Body longer than 4.5 mm (mostly> 4.8 mm)............................................................... 8

8. Dorsum usually tinged with white or ivory; pronotum with a pair of dark spots on disk.............................. 9

- Dorsum green, pale green, or yellowish green, not tinged with white (but sometimes with orange tinge); pronotum sometimes widely darkened or with dark maculae which, however, are not forming clear paired spots.......................... 10

9. Body oval; antennomere IV longer than I; paired dark spots on pronotum narrow, rectangular; restricted to silverberries, Elaegnus broadleaf trees ( Rosaceae )............................................................... N. elaegni

- Body elongate oval; antennomere IV shorter than I; pronotum with a pair of dark, semi-circular or triangular spots on disk; associated with a walnut, Juglans mandshurica ( Juglandaceae )........................... N. juglandis [part ( Fig. 3K )]

10. Body ovoid, relatively stout (cf. Fig. 3J ); clypeus entirely pale, without darkened apex; male antennomere II as long as or shorter than basal width of pronotum..................................................................... 11

- Body elongate-oval or elongate; if body ovoid and rather stout, then apical part of clypeus infuscate; male antennomere II longer than basal width of pronotum..................................................................... 13

11. Dorsum widely pale green; apex of corium narrowly darkened; currently known only from Kyushu............. N. obesus

- Clavus and apical (more than 1/4) part of corium dark brown; northern Japan..................................... 12

12. Dorsum yellowish green; apical dark macula on corium rather squared..................................... N. acelis

- Dorsum tinged with pale orange; dark macula on corium triangular or semi-circular.......................... N. ichitai

13. Dorsum almost uniformly pale green or yellowish green as in Fig. 3A–B [fading to pale or stramineous brown in dry-preserved specimens ( Fig. 4G–H )]; only apex of clypeus darkened in some species........................................ 14

- Dorsum somewhere (particularly on apex or apical part of corium) with dark spots and/or maculae.................... 25

14. Apex or apical part of clypeus infuscate.................................................................. 15

- Clypeus entirely pale, not darkened...................................................................... 18

15. Body larger (basal width of male pronotum> 2 mm)..................................... N. juglandis (pale variant)

- Body smaller (basal width of male pronotum <1.8 mm)...................................................... 16

16. Labium as long as or longer than metafemur......................... N. lobatus (pale variant with dark apex of clypeus)

- Labium shorter than metafemur......................................................................... 17

17. Male vertex wider, 0.33–0.35 times as wide as head width across eyes in dorsal view.............. N. hasegawai ( Fig. 4I )

- Male vertex narrower, less than 0.29 times as wide as head width including eyes....................... N. tiliicola [part]

18. Vertex very narrow, 0.20 times as wide as head width across eyes in dorsal view........................ N. yamatoensis

- Vertex ≥ 0.22 times as wide as head width across eyes....................................................... 19

19. Antennomere III more than 1.4 times as long as head width across eyes, about as long as basal width of pronotum................................................................................................... N. nakatanii

- Antennomere III less than 1.3 times as long as head width across eyes, shorter than basal width of pronotum............ 20

20. Antennomere II shorter than labium or metafemur.................................................. N. makiharai

- Antennomere II usually longer than labium or metafemur.................................................... 21

21. Length of antennomere II shorter than twice of head width across eyes; antennomere III shorter than head width across eyes................... N. flavoviridis ( Fig. 3A ), N. lobatus (pale variant, Fig. 3D ), N. nozakii [part], N. tomokunii or N. zhugei

- Length of antennomere II greater than twice of head width across eyes; antennomere III longer than head width across eyes22

22. Antennomere II longer than twice length of I.............................................................. 23

- Antennomere II shorter than twice length of I.............................................................. 24

23. Vertex wider than an eye in dorsal view.......................................................... N. kawasawai

- Vertex narrower than an eye in dorsal view..................................................... N. angustivertex

24. Male genitalia as in Fig. 7A–D......................................................... N . chichibumontis n. sp.

- Male genitalia as in Fig. 7E–F.................................................................... N . nozakii

25. Pronotal disk widely dark brown or reddish brown ( Fig. 3C, E, G, I )............................................ 26

- Pronotum pale, almost immaculate (e.g., Fig. 3A ), or posterior part narrowly darkened (e.g., Fig. 3H )................. 28

26. Antennomere III as long as or shorter than head width across eyes.................... N. lobatus (dark variant, Fig. 3C )

- Antennomere III obviously longer than head width across eyes................................................ 27

27. Vertex wider, 0.35–0.42 times as wide as head width across eyes in dorsal view ( Fig. 3I )....................... N. esakii

- Vertex narrower, 0.32–0.33 times as wide as head width across eyes................ N. nipponicus (dark variant, Fig. 3G )

28. Pronotum narrowly (less than posterior half) darkened along posterior margin (cf. Fig. 3H ).......................... 29

- Pronotum uniformly pale, immaculate.................................................................... 30

29. Body smaller, less than 5 mm; labium as long as basal width of pronotum; scutellum castaneous ( Fig. 5A ); currently known only from Okinawa Island of the Ryukyus..................................................... N. yonanus n. sp.

- Body longer than 5.5 mm; labium longer than basal width of pronotum; scutellum pale; cryophilic species associated with deciduous broadleaf trees or shrubs in Hokkaido and Honshu (north of Kanto area) [some specimens (with posteriorly darkened pronotum) of N. honshuensis may run to this couplet, but its labium is as long as or shorter than basal width of pronotum]............................................................................................ N. nipponicus

30. Length of antennomere II nearly equal to twice as long as III; membrane with noticeable brown spots ( Fig. 3N ); associated with alders, birches and willows in north of central Honshu............................................... N. nemoralis

- Antennomere II obviously shorter than twice length of III; membrane with less spotted pattern....................... 31

31. Apex of clypeus narrowly or faintly darkened, or entirely pale................................................. 32

- More than apical 1/5 of clypeus clearly darkened........................................................... 36

32. Body length less than 5.2 mm; antennomere II as long as or shorter than labium................................... 33

- Body longer than 5.4 mm; antennomere II obviously longer than labium......................................... 34

33. Metafemur as long as antennomere II; restricted to Hokkaido (currently known from urbanized zone of Sapporo area) and associated with Tilia spp. ......................................................................... N. vityazi

- Metafemur longer than antennomere II; Hydrangea panuculata in western Japan................ N. autumnus n. sp. [part]

34. Clavus usually more or less darkened; apical part of corium with noticeable fuscous, ovoid or semi-circular macula ( Fig. 1C ); most commonly found among Japanese congeners................................................ N. honshuensis

- Clavus always pale; apical part of corium with brown, narrow macula or small spot ( Fig. 1A, C ); distribution restricted... 35

35. Antennomere II longer than metafemur; apex of corium with a small, dark, circular or semicircular spot; currently known only from central Hokkaido and associated with Syringa reticulata .......................................... N. flaviceps

- Antennomere II as long as metafemur; apex of corium narrowly darkened ( Fig. 3L ; often faintly brown in dry-preserved specimens); associated with a horse-chestnut, Aesculus turbinata in southwestern Japan....................... N. similis

36. Antennomere II as long as or longer than metafemur............................................. N. tiliicola [part]

- Antennomere II shorter than metafemur.................................................................. 37

37. Apical fuscous macula on corium relatively large and clear (cf. Figs. IE, 4D)..................................... 38

- Apex of corium narrowly and/or faintly darkened (cf. Fig. 2A, E, G )............................................ 39

38. Vertex narrower, 0.22 (0.33–0.34 in female) times as wide as head width across eyes; currently know only from warm temperate Goto Islands in Nagasaki Prefecture ..................................................... N. chikanoshima n. sp.

- Vertex wider, 0.30–0.33 (0.34–0.37 in female) times as wide as head width across eyes; associated with blackbelly, Morus australis , in temperate and cold temperate deciduous forest zones................................... N. hakusanensis

39. Antennomere II as long as basal width of pronotum; restricted to Ryukyu Islands and known to associated with flower-buds and inflorescence of a broadleaf, Trema orientalis ( Cannabaceae )................................ N. tokaraensis ( Fig. 2G )

- Antennomere II obviously longer than basal width of pronotum................................................ 40

40. Dorsum usually tinged with olive-orange and metafemur sometimes reddish in fresh (or live) individuals; antennomere II more than 3 times as long as IV; thermophilic species propagating mainly on an evergreen Fagaceae broadleaf, Castanopsis sieboldii in warm temperate and subtropical climatic zones of southwestern Japan including the Ryukyu Islands...... N. kyushuensis

- Dorsum and metafemur pale green or yellowish green in fresh specimens; antennomere II less than 3 times as long as IV; inhabiting deciduous forests in temperate and cold temperate zones....................................... N. tiliicola

Figures

FIGURE 1. Habitus imagesof living individualsof Neolygus spp.A–B.N.autumnusn. sp.,male.C.N. honshuensis(Linnavuori). D. Same, female. E–G. N. chikanoshima n. sp., female. H. N. roseus (Yasunaga), female. I. N. fuscovultus n. sp., holotype female. J. N. chaiyaphum n. sp., holotype male.

FIGURE 2. Habitus images of living adults and final instar nymphs (C, F) of Neolygus spp. A–C. N. kyushuensis (Yasunaga). D–F. N. tiliicola (Kulik). G. N. tokaraensis (Yasunaga), female.

FIGURE 3. Habitus images of living individuals of Japanese Neolygus spp. A. N. flavoviridis (Yasunaga). C. N. hoberlandti (Kulik). C. N. lobatus (Linnavuori). D. Same, greenish variant lacking dark dorsal macula. E. N. pteleinus (Kerzhner). F. Same, pale variant lacking dark dorsal macula. G. N. nipponicus (Yasunaga), extremely darkened variant. H. Same, paler variant. I. N. esakii (Yasunaga). J. N. obesus (Yasunaga). K. N. juglandis (Kerzhner). L. N. similis (Yasunaga). M. N. longiusculus (Kulik) O. N. nemoralis (Kulik).

FIGURE 4. Ventral (E, F, H), lateral (C) and dorsal habitus images of Japanese Neolygus spp., dry-preserved specimens. A. N. autumnus n. sp., holotype male. B–C. Same, female. D–E. N. chikanoshima n. sp., male. F. holotype female. G–H. N. chichibumontis n. sp., holotype male. I. N. hasegawai n. sp., holotype male.

FIGURE 5. Frontal (G), lateral (B, L), ventral (E) and dorsal habitus images of Neolygus spp., dry-preserved specimens. A–B. N. yonanus n. sp., holotype male. C. N. kyushuensis (Yasunaga), paratype male. D–E. N. tiliicola (Kulik), male from Russian Primorsky Territory. F–G. N. babai n. sp., holotype male. H. N. formosaroseus n. sp., holotype male. I. Same, female. J. N. rufifemoratus n. sp., holotype male. K–L. Same, female.

FIGURE 6. Male (A–E, G–L) and female (F, M) genitalia of Neolygus autumnus n. sp. (A−F) and N. honshuensis (Linnavuori) (G–M).A, C, G, I. Left paramere. B, D, H, J, Right paramere. E, K, L. Vesica. F, M. Female genital chamber. Scale bars 0.2 mm. Abbreviations – GP: secondary gonopore, MS: median sclerite, PH: phallotheca, SP: spiculum, VS: ventral sclerite.

FIGURE 7. Male genitalia of chichibumontis n. sp. (A−D) and N. nozakii Yasunaga (E–F). A. Apex of genital segment (pygophore) with parameres, dorsal view. B, E. Same, ventral view. C, F. Vesica, ventral view. D, Same, dorsal view (side of secondary gonopore opening). Scale bars 0.2 mm. Abbreviations – BS: basal sclerite, GP: secondary gonopore, MS: median sclerite, PH: phallotheca, SP: spiculum, VS: ventral sclerite.

FIGURE 13. Scanning electron micrographs for Neolygus autumnus n. sp. (A−I) and N. honshuensis (Linnavuori) (J−O). A, Head and pronotum, left lateral view. B, Vestiture pattern on scutellum and anterior hemelytron. C, J, Anterior body, left lateral view. D, K, Metathoracic scent efferent system (left). F, M, Pretarsal structure of metaleg. G, Apical pygophore (genital segment) with parameres, dorsal view. H, N, Left paramere. I, O, Right paramere.

FIGURE 14. Scanning electron micrographs for Neolygus autumnus n. sp. (A−F) from Oita Pref. (A–C) and Kyoto Pref. (D–F), N. honshuensis (Linnavuori) (G−I) and N. chichibumontis n. sp., holotype male (J−O). A, D, G, O, Vesica. B, E, H, Posterior wall. C, F, I, Interramal lobe and lateral lobe of posterior wall. J, Head and pronotum, left lateral view. K, Metathoracic scent efferent system (left). L, Metatarsus. M, Pretarsal structure of metaleg. N, Apical pygophore (genital segment) with parameres, dorsal view. Abbreviations—BS: basal sclerite, GP: secondary gonopore, IRL: interramal lobe, IRS: interramal sclerite, LLB: lateral lobe, MS: median sclerite, PH: phallotheca, SP: spiculum, VS: ventral sclerite.