On a taxonomic feature that has been overestimated in classification practice: an integrative taxonomic revision of Stephoblemmus Saussure, 1877 based on morphology and molecular phylogeny (Orthoptera: Grylloidea; Gryllidae; Gryllinae)

Abstract

The hemispherical head is prevalent in Gryllinae crickets, so the rare crickets that have a unique form of head will be extremely unusual. In previous studies, this special feature can be one of the important features to distinguish and identify these crickets. But does this particular head shape truly reflect a clear-cut taxonomic relationship? The species of the genus Loxoblemmus have a typical truncate head; species of the genus Stephoblemmus have a more exaggerated truncate head, with the frontal end even extending into a lamellar. The genus Mitius is relatively unusual in that species of this genus have both globose or truncate heads. How are these species related? Does the cephalic shape perfectly reflect the natural classification of these species? Based on these questions, the study applied species definition and morphological classification to explore the intergeneric and intrageneric species relationships of the genera Mitius, Stephoblemmus, and Loxoblemmus, and derived the following main conclusions: (1) Mitius and Stephoblemmus are related and distinct from Loxoblemmus; (2) Mitius species bear two types of frons (truncated and rounded), but this feature disallows them to be classified as natural groups; (3) one genus synonym and three species synonyms are raised (Mitius Gorochov, 1985 syn. n., Mitius splendens (Shiraki, 1930) syn. n., Mitius eryuanensis Yuan, Xie & Liu, 2021 syn. n. and Mitius brevipennis Yuan, Ma & Gu, 2022 syn. n.), and seven new status combinations are proposed (Stephoblemmus blennus (Saussure, 1877) comb. n., Stephoblemmus castaneus (Chopard, 1937) comb. n., Stephoblemmus enatus Gorochov, 1994 comb. n., Stephoblemmus flavipes (Chopard, 1928) comb. n., Stephoblemmus minor (Shiraki, 1911) comb. n., Stephoblemmus minutulus (Yang & Yang, 1995) comb. n. and Stephoblemmus vaturu (Otte & Cowper, 2007) comb. n.). The studies indicated that frons shapes that appear to be significantly different might not always reflect the correct Gryllinae species relationships and a combination of more taxonomic features and taxonomic techniques is needed often to reveal the true taxonomic relationships.