Euphorbialygus, Yasunaga, 2024

Euphorbialygus , new genus

Type species. Euphorbialygus nanglong , new species.

Diagnosis. Euphorbialygus , new genus, is recognised primarily by the following characters: Ovoid body; castaneous or red-brown basic colouration; reduced basal transverse carina on vertex; dense silvery, lanceolate setae mixed with pale, simple setae on scutellum and hemelytra; rather matte hemelytra with darker spot at median to lateral parts of cuneus; and unique male and female genitalic structures as described below. Most similar in external appearance to Apolygopsis Yasunaga, Schwartz & Chérot and Apolygus China, 1941; the present new genus can be distinguished by the following combination of characters: Basal transverse carina on vertex obliterated or slightly keeled; scutellum and hemelytron with densely distributed, silvery, lanceolate setae mixed with pale, simple setae; pale brown tibial spines; short, duck head shaped hypophysis of left paramere; tiny hypophysis of right paramere; three distinct long spicules on vesica; ovoid sclerotised rings that are mesally separated to each other; and simple form of posterior wall anteriorly with a pair of small, pointed processes between interramal lobes..

Description. Body oval, relatively small (3.2–4.2 mm in total length); general colouration reddish brown or castaneous; dorsal surface weakly shining, partly matte, with uniformly distributed, pale, simple, reclining setae and densely distributed, silvery, lanceolate setae ( Figs. 24E View Fig , 25E View Fig ); significant sexual dimorphism not recognisable. Head: Vertical ( Figs. 24B View Fig , 25A View Fig ); eyes large; vertex narrow, weakly concaved mesially, lacking basal transverse carina; clypeus almost flat. Antenna: Almost linear, slightly shorter than body, generally slender, not incrassate; antennomere I reddish brown, with darkened basal half; antennomeres II–IV dark brown; antennomere II with pale reddish basal half and darkened extreme base, slightly longer (male)/ shorter (female) than basal width of pronotum; antennomeres III and IV filiform. Labium: Relatively slender, reaching but not exceeding apex of metacoxa, slightly shorter than metafemur. Thorax: Pronotum shining, with uniformly distributed, pale, simple, reclining setae, sparsely and shallowly punctate, without silvery setae; calli weakly demarcated; collar flat, about as thick as antennomere III, with sparse, short, upright setae; scutellum pale brown, shallowly and transversely rugose; pleura pale brown; metathoracic scent efferent system creamy yellow, subtriangular, with narrow, somewhat convex peritreme ( Figs. 24C View Fig , 25G View Fig ). Hemelytron: Weakly shining, matte, with uniformly distributed, minute, circular punctures and with both pale simple setae and silvery setae; cuneus more or less suffused with red. Legs: Pale brown; each femur with several obscure annulations; tibial spines pale reddish brown, rather short; meta-tarsomere I about half as long as II or III; parempodia lanceolate. Male genitalia: Left paramere L-shaped, with developed, with elongate hypophysis terminated in apical hook; right paramere almost straight, with tiny hypophysis; vesica with two spicules and a flagellate lobal-sclerite; seminal duct weakly inflated apically; secondary gonopore circular; phallotheca smooth. Female genitalia: Sclerotised rings oval, thick-rimmed, separated from each other mesially; posterior wall relatively simple in form, anteriorly with a pair of small, pointed processes between interramal lobes, lacking dorsal structure nor lateral lobe; interramal lobe narrow, with sparsely distributed, scaly microstructures along posterior margin.

Etymology. Named for the plant associations of the known congeners with Euphorbiaceae broadleaf angiosperms, combined with the mirine generic name Lygus Hahn ; gender masculine.

Discussion. Judging from the patterns of vesical sclerites, Euphorbialygus , new genus, appears to be related to Apolygopsis Yasunaga, Schwartz & Chérot and Apolygus China. Nonetheless, presence of the silvery, lanceolate setae on the dorsum and the form of the female genitalia (e.g., ovoid, mesally separated sclerotised rings and wider interramal lobes on posterior wall) in Euphorbialygus , new genus, are evidently different from those of the two known genera.

Euphorbialygus , new genus, currently comprises two thermophilic members, associated with Euphorbiaceae hosts and distributed in the southern foothills of the Himalayas and Indochina.