Account
What the sources say about this taxon, as written.
discussion · 
Plazi
Comparison with similar genera. Rhicnogryllus (sensu R. bipunctatus ) has similar genitalia morphology as Trigonidium and Svistella Gorochov, 1987 but differs from Trigonidium by virga long (usually shorter than rachis in Trigonidium ). Rhicnogryllus also differs from Trigonidium ( Paratrigonidium Brunner von Wattenwyl, 1893 ) and Svistella by absence of stridulatory organs in males (see Gorochov, 1987 ; Tan & Robillard, 2012 ; Lu et al. , 2018 ; Tan et al. , 2019a ).
description · Plazi
Description. Very small crickets, even among Trigonidiinae . Head, together with eyes, clearly wider than pronotum. Frontal rostrum flattened, only slightly wider than scapus; with a few long setae. Vertex flattened dorsally, with a few strong long setae. Antennal segments, including scapus, pubescent. Eye very large, protruding laterally, from dorsal view slightly elongated; in lateral view slightly hemispheric. Gena swollen, not pubescent. Maxillary palpi elongated; last three segments of about equal length; apical segment triangular, longer than wide, with apex truncated. Labial palpi with apical segment long and slightly swollen at the apex. Pronotum wider than long; with a few long setae but more pubescent along margins; sulci distinct or indistinct; anterior and posterior margins straight; dorsal disc flattened. Lateral lobe of pronotum longer than high, ventral margin straight or sinuous, anterior and posterior angles obtuse; anterior angle with numerous strong long setae, posterior margin lined with shorter setae. Without visible metanotal gland. Male and female tegmina in lateral view appears rounded, not pubescent; reaching abdominal apex, but not covering epiproct; without stridulatory apparatus in males; apex somewhat truncated. Tegminal dorsal field with 7 longitudinal, elevated and parallel veins, lateral field with 3 or 4 less-elevated and slightly sinuous veins; without cross-vein. Hind wing absent. Legs generally pubescent and with long setae. Fore tibia with both tympana absent. Tarsal middle segment with prominent adhesive pad. Hind tibia with three inner and three outer subapical spurs; two inner and two to three outer apical spurs, inner ones distinctly longer than outer ones. Female: Not different morphologically as the males, including tegmina. Ovipositor short, barely reaching apex of cercus; basal half straight and apical half slightly curved dorsad; ventral and dorsal margins usually dentated; ventral valve surpassing usually dorsal valve, apex acute. Colouration: Highly variable, but often with contrasting colour patterns. Exhibit sexual dimorphism in some species—typically with females having darker colouration (e.g., Rhicnogryllus fascipes Chopard, 1925 )—but not others (e.g., Rhicnogryllus bipunctatus Ingrisch, 1987 ). Hind femur usually pale colour with two black bands, one in the middle, and another either before or after middle.
discussion · Plazi
Remarks. Genitalic morphology generally exhibits intraspecific stability and distinct interspecific differences in orthopterans, and this probably is also true for Trigonidiinae ( Gorochov, 2015a ; Gorochov, Tan, & Lee, 2018). This genus seems by distributed throughout world and is classified only by the presence of parallel and elevated veins in both males (absent of stridulatory vein) and females ( Tan et al ., 2020 ). However, the male genitalia were rarely used previously. With details of the males genitalia known for only six species. With each species, the male genitalia seem very distinctive. This presents a challenge for the future.