Metrodorini Bolívar, 1887

Kasalo, Niko, Yong, Sheyla, Rebrina, Fran & Skejo, Josip, 2023, Definition of the tribe Metrodorini (Orthoptera: Tetrigidae) with notes on biogeography and evolution of Metrodorinae and Cladonotinae, Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 63 (1), pp. 187-193 : 188-190

Tribe Metrodorini Bolívar, 1887

Metrodorini Bolívar, 1887 . Type genus: Metrodora Bolívar, 1887 .

= Miriatrini Cadena-Castañeda & Cardona 2015, syn. nov. Type genus: Miriatra Bolívar, 1906 ; STOROZHENKO (2016); SILVA et al. (2017)

= Mucrotettigini Cadena-Castañeda & Silva, 2019, syn. nov. Type genus: Mucrotettix Perez-Gelabert, Hierro & Otte, 1998

Composition and distribution. Widely distributed throughout the northern half of South America, including Central America, and the Caribbean. The following genera are present on the mainland: Cota Bolívar, 1887 ; Hancockiella Cadena-Castañeda & Cardona, 2015 ; Metrodora Bolívar, 1887 ; and Miriatra Bolívar, 1906 . The following genera, formerly included in the tribe Mucrotettigini , are present in the Caribbean: Antillotettix Perez-Gelabert, 2003 ; Armasius Perez-Gelabert & Yong, 2014 ; † Baeotettix Heads, 2009 ; Bahorucotettix Perez-Gelabert, Hierro & Otte, 1998 ; Cubanotettix Perez-Gelabert, Hierro & Otte, 1998 ; Cubonotus Perez-Gelabert, Hierro & Otte, 1998 ; † Electrotettix Heads & Thomas, 2014 ; Haitianotettix Perez-Gelabert, Hierro & Otte, 1998 ; Hottettix Perez-Gelabert, Hierro & Otte, 1998 ; Mucrotettix Perez-Gelabert, Hierro & Otte, 1998 ; Sierratettix Perez-Gelabert, Hierro & Otte, 1998 ; Tiburonotus Perez-Gelabert, Hierro & Otte, 1998 ; and Truncotettix Perez-Gelabert, Hierro & Otte, 1998 .

Diagnosis. The upper margin of the vertex is approximately at the level of the upper margin of the compound eyes. The eyes are set wide apart, i.e., the vertex is approximately two or more times wider than the eye. The carinae of the vertex are produced, with lateral carinae forming more or less pronounced horns and the medial carina visibly compresso-elevated, extremely so in Miriatra . In lateral view, the medial carina protrudes beyond the eyes and is at least slightly visible. The placement of the bifurcation of the frontal costa varies from around mid-level of the eyes to below the bottom margin of the eyes. The scutellum is usually wider than multiple widths of the scape, but there are rare exceptional species with a narrow scutellum. The upper margins of the antennal grooves are below the bottom margins of the eyes. Antennae are usually short, 10 to at least 15-segmented, but the precise upper boundary is hard to determine because the types usually lack antennae and the original descriptions do not describe them in detail. The median carina of the pronotum is arcuate, forming a more or less pronounced crest. The lateral lobes of the pronotum are usually projected outwards to varying degrees. The lateral lobes are occasionally in the form of sharp spines. Most species are apterous, except for the species of the genera Electrotettix and Miriatra .

Comparative notes. The main difference that separates Metrodorini from Cladonotini is the morphology of the head. In frontal view, Cladonotini have a smooth vertex that bulges upwards, while Metrodorini have the characteristic three protrusions formed by lateral and medial carinae of the vertex. In lateral view, the distant eye of Cladonotini is obscured by the bulging part of the vertex, while the distant eye of Metrodorini is either visible or obscured by the thin elevated medial carina. The tribe Choriphyllini , the only true Caribbean cladonotines, have a highly specialized leaf-like morphology and are thus both easy to differentiate from and difficult to compare to the other taxa present in the region.

Compared to Batrachideinae ( TUMBRINCK 2014), Metrodorini and Cladonotini are not as robustly defined but the herein presented diagnosis offers several independent characters that should mitigate the confusion of classifying similar genera in the future. A visual comparison of the heads of Metrodorini , Cladonotini , and Choriphyllini is available in Fig. 1 .

The original diagnosis by SILVA et al. (2019) compares the tribe Mucrotettigini only to the tribe Choriphyllini , noting that they are easily separated because the latter tribe exhibits leaf-like morphology. That diagnosis does not take into account the type specimens of either Metrodorinae or Cladonotinae and thus fails to provide evidence for the subfamilial classification of Mucrotettigini . The original description of Mucrotettigini for the most part fits with the herein presented diagnosis of Metrodorini , differing only in its description of the length of the pronotum and the shape of the legs as important characters. We expand the definition of the tribe by not considering the latter two characters diagnostic. The reasoning for this decision is provided in the Discussion.

Figures

Fig. 1. A comparison of drawings traced over the type specimens of the species representing the tribes Metrodorini, Cladonotini, Choriphyllini, and a single species placed under Cladonotinae without tribal assignment: Eleleus curtus Bolívar, 1887. The drawings represent the key morphological features of the head, namely the compound eye (c), the position of the antennal groove (ag), the shape of the vertex (v), and the facial carinae (fc). The drawings were adapted after the photographs taken by Josef Tumbrinck, Daniela Silva, and Marcelo Pereira, available in the Orthoptera Species File (CIGLIANO et al. 2022).