Diognetus minusculus, Yasunaga & Schwartz & Chérot, 2023

Yasunaga, Tomohide, Schwartz, Michael D. & Chérot, Frédéric, 2023, Revision of the plant bug genus Diognetus, with descriptions of thirteen new species from the Oriental and Eastern Palearctic Regions (Hemiptera: Heteroptera: Miridae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 63 (1), pp. 1-55 : 30-36

Diognetus minusculus sp. nov.

( Figs 17A− C, 18, 33)

Type material. HOLOTYPE: J, MALAYSIA: PERAK: Taiping, Bukit Larut (Maxwell Hill), 4.8625, 100.8000, 1100 m, mercury light trap, 21 Aug 1990, T. Yasunaga ( ZRC) ( AMNH _ PBI 00380752 ) . PARATYPES: MALAYSIA: Same data as for holotype, 2 JJ 3 ♀♀ ( DOAT, TYCN); same data, except for date 29 Dec 1989, 1 ♀ ( TYCN).

Additional material examined: INDONESIA: NORTH SUMATRA: Brastagi, North of Toba Lake, 3.18°N, 98.50°E, 1,400 m, at FL light, 5–9 Dec 1989, T. Yasunaga, 1 ♀ ( TYCN).

Description. Body ovoid, small, 3.5−4.2 mm in total length; smallest species among known congeners. COLORATION: Body generally brown to dark brown ( Figs 17A− B); dorsum partly speckled with darker maculae. Head pale brown; vertex and frons somewhat darkened medially; clypeus sometimes suffused with red. Antennae pale brown; segment I partly darkened; apical 1/4−1/3 of segment II, and whole segment III (except for yellowish extreme base) and segment IV dark brown. Labium shiny pale reddish-brown; apex of segment IV narrowly dark brown ( Fig. 17C). Pronotum relatively shining, brown, more or less darkened posterolaterally, with creamy yellow posterior margin; calli with a pair of dark, shiny spots; mesoscutum and scutellum grayish brown; pleura, except for brown propleuron, shiny black; scent efferent system creamy yellow, weakly tinged with red in some specimens. Hemelytron irregularly mottled with dark maculae; cuneus reddish-brown, with paler basal 2/3; membrane smoky brown, with pale veins and several semitransparent spots. Coxae and legs whitish brown; apical half of metafemur brown, with two faint pale rings subapically; apices of tibiae and tarsomeres III darkened. Ventral surface of abdomen almost uniformly pale brown. SURFACE AND VESTITURE: As in generic diagnosis; scutellum finely and uniformly punctate, less rugose ( Fig. 33A); hemelytron matte; punctures on corium partly sparse and shallow. STRUCTURE: Vertex wider than an eye in dorsal view, with narrow basal transverse carina ( Fig. 33D). Antennal segment II obviously shorter than labium. Labium long, reaching apex of mesocoxa but not exceeding apical metacoxa ( Figs 17C, 33C). Pronotum and propleuron uniformly punctate ( Figs 33B− C); scutellum rather flat ( Figs 33B, E); metathoracic scent efferent system as in Fig. 33F. Pretarsal structure as in Fig. 33I; parempodia rather long and broad. MALE GENITALIA ( Figs 18A− D, 33G, J− K): Left paramere modified in shape, with triangular protuberance of sensory lobe and somewhat flattened hypophysis that is hooked at apex ( Figs 19A, 36J); right paramere relatively elongate ( Figs 18B, 33J). Vesica ( Figs 18C− D) heavily sclerotized, with a distinct spicule ( Fig. 33K); RS with two apical pointed processes; secondary gonopore small. FEMALE GENITALIA ( Figs 18F–G, 33L− O): Sclerotized ring comparatively large ( Figs 18F, 33L); posterior wall ( Figs 18G, 33M− O) with moderately developed dorsal structure that is covered with scaly microstructures ( Fig. 33N); interramal lobe wide, semi-circular ( Fig. 33M), not spinulate but densely furnished with scaly microstructures ( Fig. 33O).

Measurements. See Table 1.

Differential diagnosis. Recognized by its tiny size; short antennal segment II with darkened apical 1/4−1/3; generally whitish brown femora; and unique shape of male and female genitalia as described above. At first sight similar to D. duwalorum sp. nov. ( Nepal), from which this new species can be distinguished by the darker dorsum, dark apical part of antennal segment II, and shorter labium.

Etymology. From Latin, minusculus (very small), referring to its smallest size among known congeners; adjective.

Biology. Unknown; all available individuals were collected at UV (mercury) lights, facing to a tropical rain forest.

Distribution. Malaysia (Perak), Indonesia (North Sumatra).

Comments. Based on the shape of the male genitalia, this new species is most closely related to D. flavigenis ( Japan) and D. puspae sp. nov. ( Nepal), although the external appearance of each species is distinctive (e.g., body size, color pattern of femora). The distribution pattern of the three related species may imply faunal relationships between the Himalayas and eastern (and SE) Asia.