Guntheritettiginae, Cadena-Castañeda & Quintana-Arias & Infante & Silva & Tavares, 2025

Cadena-Castañeda, Oscar J., Quintana-Arias, Ronald Fernando, Infante, Ivette Coque, Silva, Daniela Santos Martins & Tavares, Gustavo Costa, 2025, Studies on pygmy grasshoppers: On the current Metrodorinae sensu lato classification (Orthoptera: Tetrigidae) with emphasis on American and Malagasy taxa, Zootaxa 5597 (1), pp. 1-265 : 246-247

About Metrodorinae s. l.

The Metrodorinae s. l. are the taxa currently included within the subfamily, which were grouped in the Old World after this contribution. Like many of the tetrigid taxa, a revision of the genera is necessary to understand the composition of the taxonomic diversity, concentrating mainly in Southeast Asia. The study of the taxa is beginning progressively; here, we contribute with the Malagasy taxa, from which two new subfamilies of very particular morphology were proposed, Guntheritettiginae subfam. nov. (two tribes, 14 genera and 34 species) from Madagascar, and Hildegardiinae subfam. nov. (one tribe, one genus, and three species) from Mauritius and the Reunion Islands. Both subfamilies proposed here as new are evidence of the need to review the Metrodorinae s. l., which in this case diversified in isolated sites of the Indian Ocean.

Hildegardiinae subfam. nov. is notably differentiated from the rest of the world tetrigids, inhabiting Mauritius and Reunion. Of the three known species, the most morphologically related are H. mauritiivaga and H. reuniivaga , from different islands, as indicated by their specific epithets. The opposite of what might be expected happens with H. mauritiivaga since it inhabits the same island as H. mauritiicola . However, they are different from each other ( Hugel, 2007; 2014). The differentiation of this subfamily is evidenced in the comparison section of this contribution, ruling out, for now, its affiliation with Batrachideinae or Scelimeninae , as Günther (1974) suggested. Once it does not fit into the definition of these two subfamilies, nor into that of Metrodorinae s.s., designate Hildegardiinae subfam. nov. as a new subfamily was necessary. The species of this new subfamily camouflage themselves with lichens and bryophytes of these islands, adding this to the peculiar morphology that characterizes them ( Hugel, 2014). Mauritius, Reunion, and Rodriguez Islands are part of the Mascarene Islands, small islands that host a high degree of endemism and that are also vulnerable to anthropogenic dynamics that can easily harmfully affect the biodiversity if there is not adequate conservation of their ecosystems, unique on the planet ( Hugel, 2015; Florens, 2013a, b). The only genus included, Hildegardia was dedicated by Günther (1974) to his beloved wife, who had died shortly before. Klaus Günther would probably be happy that this vow of his love for his beloved wife was included in its own subfamily.

The members of Guntheritettiginae subfam. nov. are distinguished by various characters, as mentioned in the comparison of the original description. Some of the members of this subfamily, especially the tribe Guntheritettigini trib. nov., were considered as the group of “ Metrodorinae of Madagascar,” so their possible differentiation from other suprageneric taxa was hypothesized ( Günther, 1939, 1959, 1974; Devriese, 1991; Skejo et al., 2020). In addition, the spine-like ornament of the lateral carinae is admirable, which can vary into notable undulations, as well as conspicuous humps ( Rehn, 1929; Devriese, 1991; Günther, 1959). Some species are colorful, something unusual in tetrigids ( Skejo et al., 2020). The pygmy grasshoppers of the tribe Tumbrinckitettigini trib. nov. are thinner, unlike the other tribe of the subfamily; they are easily differentiated because of their slenderer bodies, and it is expected to observe conspicuous spine-like projections on the lateral lobes of the pronotum. Some of the taxa were considered to have a scelimeloid shape ( Rehn, 1929; Günther, 1959, 1974), which is something interesting for future phylogenetic proposals to compare with the Scelimeninae . It is worrying that the notable diversity of tetrigids in Madagascar (that is higher than in some continental areas) is being affected by the high deforestation of the island, which can push the extinction of members of this and other wonderful biological groups of the place ( Harper et al., 2008; Suzzi-Simmons, 2023) Most species have not been recorded since the original description, which was sometimes made with very old specimens ( Rehn, 1929, 1937). This may be due to the little material collected in Madagascar or the possible disappearance of many of these species, which would be tragic and pushes us to document biodiversity before it completely disappears ( Ralimanana et al., 2022; Suzzi-Simmons, 2023).

In Madagascar and adjacent islands, there are still tetrigids that remain in Metrodorinae s. l. ( Cigliano et al. 2024). They do not fit the definition presented here for the subfamily or the other subfamilies recorded for the area. For example, the tribe Pterotettigini trib. nov. does not fit the definition of Guntheritettiginae subfam. nov., but it has similarities with Asian taxa, so it is not advisable to propose a new subfamily for this group until its relationship with Asian taxa is clarified. Furthermore, Arexion is a genus that is not included in any tribe but shares characteristics with Spartolus ( Rehn 1929) , which leaves doubt of possible transoceanic colonization. If so, Arexion , as a monotypic genus, prevails in Madagascar, in contrast to the highly diversified Ophiotettigini in Southeast Asia ( Tumbrinck & Skejo, 2017).

In addition to the proposed tribes defined here for Metrodorinae s. l., two well-defined tribes are found in Asia: Clinophaestini and Ophiotettigini . Clinophaestini groups two monotypic genera from Myanmar and Thailand (possibly also occur in Laos and southern China). Their robust appearance and peculiar antennae distinguish them. They were originally included in the subfamily Tripetalocerinae ( Storozhenko, 2013) and were recently moved to Metrodorinae by Tumbrinck & Skejo (2017). The recently established subfamily Ophiotettigini consists of six genera, of which the most diverse is Ophiotettix Walker, 1871 (pygmy giraffe-hoppers), with 43 species ( Tumbrinck & Skejo, 2017). The Ophiotettigini are distributed mainly in Southeast Asia, and additional taxa should be incorporated in the future, each time refining the classification of the tribes of this region. Apart from these two tribes, there is also Cleotrastini, a tribe that must be reevaluated, and with taxa outside Asia ( Silva et al., 2017), grouping eleven genera (except Metopomystrum , now with its own tribe). Also, numerous genera without tribal affiliation must be reviewed and delimited.

In Oceania, the diversity of Metrodorinae s. l. is smaller compared to the other continents, hosting some species of Amphinotus (Melanesia Islands, not including New Guinea) and Austrohyboella Rehn, 1952 ( Australia). According to the OSF ( Cigliano et al., 2024), the genera not included in any subfamily but that were originally included in Metrodorinae that also inhabit Australia are: Cyphotettix Rehn, 1952 , Peronotettix Rehn, 1952 , and Euloxilobus Sjöstedt, 1936 ( Rehn, 1952; Sjöstedt, 1936). Therefore, at least four genera are found in the continental area and two more in the adjacent islands. Probably, with future studies, these taxa should be reassigned and redefined.

Possibly, the Metrodorinae in Africa are absent. Although some African taxa are still placed in this subfamily, many of these are included in Cleotrastini or are not in any other tribe and must be reassigned to other subfamilies (Cadena-Castañeda, in prep.). In this way, taxa from other subfamilies, such as Tetriginae or Cladonotinae s. l. are the most predominant in the faunas of Africa and Oceania, reinforcing our hypothesis of American distribution of the Metrodorinae s. l.