Idiocysta takarai, Souma, 2020

Souma, Jun, 2020, Discoveries of the genera Baeochila and Idiocysta from Japan, with descriptions of two new species (Hemiptera: Heteroptera: Tingidae), Zootaxa 4731 (3), pp. 388-402 : 394-399

Idiocysta takarai sp. nov.

( Figs. 3 A–J, 4A–C, 5A, B, 6C, D)

Type series. HOLOTYPE (macropterous ♂), JAPAN: Ryukyu Islands : Iriomote Is., Tomori, 24°23’47.4”N 123°48’09.7”E, 21.xi.2018, leg. J. Souma ( TUA) . PARATYPES (macropterous 65 ♂♂ 85 ♀♀), JAPAN: Ryukyu Islands: as holotype (18 ♂♂ 26 ♀♀, TUA) ; as holotype but 19.xi.2018 (7 ♂♂ 8 ♀♀, TUA) ; Iriomote Is., Otomi For. Rd. , 24°17’54.8”N 123°51’12.2”E, 20.xi.2018, leg. J. Souma (7 ♂♂ 9 ♀♀, TUA) ; Iriomote Is., Mt. Uehara , 24°25’11.2”N 123°47’21.4”E, 21.xi.2018, leg. J. Souma (3 ♂♂ 1 ♀, TUA) ; Iriomote Is., Sonai , 29.iii.2019, leg. Y. Tamadera (2 ♂♂ 2 ♀♀, HNHM) ; Ishigaki Is., Mt. Yarabu , 24°26’26.7”N 124°05’23.2”E, 12.xi.2018, leg. J. Souma (13 ♂♂ 17 ♀♀, TUA) ; as above but 13.xi.2018 (8 ♂♂ 16 ♀♀, TUA) ; Ishigaki Is., Banna-dake , 16.xi.1984, leg. M. Tomokuni (1 ♂, NSMT) ; Ishigaki Is. , 20.iii.1960, leg. T. Takara (6 ♂♂ 6 ♀♀, ELKU) . A total of 12 specimens deposited in ELKU were labeled with an inscription of “ Idiocysta takarai Takeya, 1962 ” (manuscript name).

Additional specimens examined. Fifth instar nymph (28 spec.) , JAPAN: Ryukyu Islands : as holotype (12 spec., TUA) ; as holotype but 19.xi.2018 (3 spec., TUA) ; Iriomote Is. , Mt. Uehara, 24°25’11.2”N 123°47’21.4”E, 21.xi.2018, leg. J. Souma (2 spec., TUA) ; Ishigaki Is. , Mt. Yarabu, 24°26’26.7”N 124°05’23.2”E, 12.xi.2018, leg. J. Souma (6 spec., TUA) ; as above but 13.xi.2018 (5 spec., TUA) . These 28 specimens are nymphs, so that they are excluded from the type series.

Diagnosis. Recognized among other species of Idiocysta by a combination of the following characters: general color yellowish white ( Figs. 3 A–D); head with five spines ( Fig. 3E ); rostrum reaching posterior margin of metasternum ( Fig. 3F ); paranotum with 4 rows of areolae at widest part; outer margins of paranota touching each other throughout their length; anterior margin of hemelytron strongly curved inward in basal part; costal area of hemelytron with 3 rows of areolae at widest part ( Fig. 3H ).

Description. Macropterous male. General color yellowish white; head, pronotal disk and calli fuscous; compound eyes dark red; thoracic sterna and abdomen black; pubescence on body yellowish ( Figs. 3 A–D).

Body covered with minute pubescence, 2.6 times as long as maximum width across hemelytra ( Fig. 3A ). Head ( Fig. 3E ) stout, with five spines; a pair of frontal spines touching each other at apices, reaching beyond tip of tylus; median spine shortest among cephalic spines, slightly curved downward, extending beyond bases of frontal spines; a pair of occipital spines slightly curved inward, resting on vertex throughout their length, reaching middle of compound eyes; antenniferous tubercles obtuse, slightly curved inward; juga smooth on surface. Compound eyes prominent laterally, round in dorsal view. Antennae ( Fig. 3A ) smooth on surface; segment I approximately 3.1 times as long as its width; segment II cylinder-shaped, 2.3 times as long as its maximum width; segment III longest among antennal segments, 2.8 times as long as maximum width of head across compound eyes; segment IV fusiform, widest a little beyond middle, irregularly covered with long pubescence; ratios of lengths from segments I–IV as 1.4: 1.0: 7.0: 3.5. Bucculae long, approximately 3.3 times as long as their maximum height, with 3 rows of areolae at widest part. Rostrum ( Fig. 3F ) approximately 0.6 times as long as antennae, reaching posterior margin of metasternum.

Pronotum ( Figs. 3A, B, G ) 1.5 times as long as maximum width across paranota. Pronotal disk coarsely punctate. Hood roof-shaped; anterior margin obtusely protruded forward, only concealing basal part of vertex. Pronotal carinae with a single row of rectangular areolae throughout their length; median carina straight, extending to apex of posterior process, higher than hood at maximum height; lateral carinae nearly parallel to each other throughout their length, concealed by paranota throughout their length. Calli coarsely punctate. Paranota widest at middle, with 4 rows of areolae at widest part, approximately 2.7 times as long as their maximum height, completely covering pronotal disk throughout their length, not touching pronotal carinae; outer margins strongly curved upward throughout their length, touching each other throughout their length. Posterior process triangular, 1.1 times as wide as its length.

Hemelytron ( Figs. 3A, B, H ) narrow, 2.6 times as long as its maximum width, considerably extending beyond apex of abdomen; maximum width across hemelytra 1.5 times as much as maximum width across paranota; anterior margin strongly curved inward in basal part and nearly straight in remaining parts; costal area considerably wider than subcostal area throughout its length, slightly reflexed upward in basal part, with 3 rows of areolae at widest part; subcostal area 0.4 times as wide as discoidal area at middle of hemelytron, with a single row of areolae in apical part and 2 rows in remaining parts; discoidal area distinctly expanding beyond middle of hemelytron, with 5 rows of areolae at widest part; sutural area well-developed, with 5 rows of areolae at widest part; hypocostal lamina apparently lower than costal area at middle of hemelytron.

Thoracic pleura coarsely and evenly punctate ( Fig. 3B ). Sternal laminae ( Fig. 3F ) apparently lower than bucculae; pro- and mesosternal laminae nearly parallel to each other, open in both anterior and posterior ends; metasternal laminae as high as mesosternal laminae, open at anterior end, angularly curved inward at posterior end. Legs smooth on surface; femora thickest at middle ( Fig. 3A ).

Abdomen ellipsoidal, 1.5 times as long as its maximum width. Pygophore ( Figs. 3I , 6B ) compressed dorsoventrally, semicircular in ventral view, slightly concave at anterior margin of dorsum, with distinct transverse wrinkles on surface. Paramere ( Figs. 6A, B ) thick and long, strongly expanded in middle part, strongly curved inward in apical part; outer half and inner margin covered with pubescence in middle part; suspensory arms of parameres completely visible in dorsal view.

Measurements (holotype). Body length with hemelytra 2.4 mm; maximum width across hemelytra 0.9 mm; pronotal width across paranota 0.6 mm.

Macropterous female. General appearance very similar to that of male ( Figs. 3C, D ) except for the following characters: abdomen with ovipositor at apical part ( Fig. 3J ); apical margin of abdomen round, weakly concave at apex.

Variations in both sexes (holotype and 150 paratypes). Body length from 2.4 to 2.6 mm; maximum width across hemelytra from 0.9 to 1.1 mm; pronotal width across paranota from 0.6 to 0.7 mm.

Brachypterous morph unknown in both sexes.

Fifth instar nymph. General color yellowish white; posterolateral angles of pronotum, apical part of mesonotal wing pads and center part of abdominal tergites dark yellow; compound eyes light red ( Fig. 4 A–C). Body oval in shape, covered with minute pubescence; dorsum with countless granular projections on surface; length from 1.5 to 1.7 mm. Head with five spines. Antennae smooth on surface; segments I separated from each other at their bases; segment II shortest among antennal segments; segment III longest among antennal segments; segment IV longer than segment I. Rostrum reaching posterior margin of metasternum. Pronotum with two pairs of spines along median line of body; anterior pair on anterior part; posterior pair on middle part. Mesonotum with a pair of spines on posterior part; wing pad reaching anterior margin of abdominal tergite V. Metanotum with a pair of spines on posterior part; wing pad concealed by mesonotal wing pad throughout their length. Legs smooth on surface, longer than rostrum. Abdomen longer than total length of head and thorax except mesonotal wing pad; tergite I with a pair of spines on posterior part; tergites II and V–VIII with a single spine along median line of body; tergites IV–IX with a pair of spines on posterolateral angles.

Remarks. Idiocysta species were diagnosed by previous authors based on the differences of the morphological characters such as the presence or absence of cephalic spines, the length of rostrum, the shape of pronotum, and the areolae of hemelytron ( China 1930; Drake & Poor 1943; Guilbert 1999, 2001). These characters are also useful in the identification for the new species. In addition, the curvature of hemelytral anterior margin is also considered to be a good character in identification of the new species.

In the presence of cephalic spines and the shape of the paranotum, Idiocysta takarai sp. nov. resembles I. fijiana , but the former can be distinguished from the latter by at least five characters: general color yellowish white ( Figs. 3 A–D); rostrum reaching posterior margin of metasternum ( Fig. 3F ); paranotum with 4 rows of areolae at widest part; anterior margin of hemelytron strongly curved inward in basal part; costal area of hemelytron with 3 rows of areolae at widest part ( Fig. 3H ). On the other hand, I. fijiana has the following features: general color black; rostrum reaching posterior part of prosternum; paranotum with 5 rows of areolae at widest part; anterior margin of hemelytron slightly curved inward in middle part; costal area of hemelytron with a single row of areolae throughout its length.

Distribution. Japan (Ryukyu Islands: Ishigaki Island, Iriomote Island) ( Figs. 7A, C ).

All seven described species of Idiocysta , namely, I. bicolor , I. dryadis , I. fijiana , I. floris , I. hackeri , I. vanuana , and I. vanuatuensis , are distributed in Fiji, Samoa, and Vanuatu ( China 1930; Drake & Poor 1943; Guilbert 1999, 2001). The new species, however, inhabits the laurilignosa ecosystem of the Ryukyu Islands with a subtropical climate and is the first representative of Idiocysta from the Oriental Region as well as the Northern Hemisphere. Thus, by the discovery of I. takarai sp. nov. the distribution of Idiocysta species is disjunct between the Ryukyu Islands and the South Pacific Islands, but potentially further undescribed species are expected from the tropical and subtropical zones of the Old World.

Interestingly, although I. takarai sp. nov. was found far away from the distribution range of the seven described congeners, it matches well the above definition of the genus. The enigmatic distributional range of Idiocysta species is along the Palaeoequator. This is similar to some plant taxa that are disjunctly distributed in the tropical and subtropical zones slightly affected by the climatic changes from the Cretaceous to the Quaternary (cf. Maekawa 1960a, 1960b). Therefore, it seems that I. takarai sp. nov. from the Ryukyu Islands and the seven described congeners from the South Pacific Islands are closely related, and this new species is considered to be a relic species of the Ryukyu Islands.

Etymology. This new species is named in honor of Tetsuo Takara, a late Japanese zoologist, honoring his outstanding efforts in the Zoological exploration of the Ryukyu Islands, Japan (e.g., Takara 1954).

Host plant. Freycinetia formosana Hemsl. (Pandanaceae) ( Fig. 5C ) was confirmed as a host plant for the new species by Masaaki Tomokuni and me independently. Although Cottothucha minor Guilbert, 2006 is collected from Freycinetia sp. in Papua New Guinea ( Guilbert 2006), Idiocysta takarai sp. nov. is the first documented species seen feeding on the pandanaceous plants in the family Tingidae , whereas host plants of other congeners are known to belong to various plants of three Myristicaceae , Myrtaceae , and Zingiberaceae (cf. Guilbert 2001).

Biology. All specimens of Idiocysta takarai sp. nov. were collected from the underside of leaves of the host plant Freycinetia formosana . Similarly, other congeners have been collected from the leaves of their presumed host plants (cf. Guilbert 2001), suggesting that Idiocysta species appears to feed on the underside of leaves as do many tingids ( Schuh & Slater 1995). Adults were collected in November and March, and nymphs were observed in November.

Figures

FIGURE 3. Habitus images of Idiocysta takarai sp. nov. from Japan. Dried specimens, dorsal and lateral views: male from Iriomote Island, Ryukyu Islands (A, B) and female from Ishigaki Island, Ryukyu Islands (C, D). Cephalic structures, dorsal and ventral views (E, F). Pronotum (paranota opened) and hemelytron, dorsolateral view (G, H). Apical part of abdomen, ventral view: male (I) and female (J). Scale bars: A–D, 1.0 mm; E–J, 0.2 mm.

FIGURE 4. Fifth instar nymph of Idiocysta takarai sp. nov. from Ishigaki Island, Ryukyu Islands, Japan, dorsal, dorsolateral and lateral views (A–C). Scale bar: 1.0 mm.

FIGURE 5. Habitus images of a living adult (A) and a living fifth instar nymph (B) for Idiocysta takarai sp. nov. from Ishigaki Island, Ryukyu Islands, Japan (photographs taken indoor). Host plant (Freycinetia formosana Hemsl.) (C) of I. takarai sp. nov. at Ishigaki Island, Ryukyu Islands, Japan.

FIGURE 6. Male terminalia of Baeochila horvathi sp. nov., dorsal view: paramere (A) and pygophore (B). Male terminalia of Idiocysta takarai sp. nov., dorsal view: paramere (C) and pygophore (D). Scale bars: A, C, 0.1 mm; B, D, 0.2 mm.

FIGURE 7. Distribution map for species of Baeochila and Idiocysta from Japan (A); detail distribution records for B. horvathi sp. nov. from Japan proper (B); detail distribution records for I. takarai sp. nov. from Ryukyu Islands (C). Collecting site of B. horvathi sp. nov. = red icons; collecting site of I. takarai sp. nov. = green icons; holotype localities = circle; paratype localities = triangle.