Abstract. The classification of the largest subfamily of leafhoppers, Deltocephalinae, including 38 tribes, 923 genera, and 6683 valid species, is reviewed and revised. An updated phylogeny of the subfamily based on molecular (28S, Histone H3) and morphological data and an expanded taxon sample (37 taxa not included in previous analyses) is presented. Based on the results of these analyses and on the morphological examination of many representatives of the subfamily, the classification of the tribes and subtribes of Deltocephalinae is revised. Complete morphological descriptions, illustrations, lists of the included genera, and notes on their distribution, ecology, and important vector species are provided for the 38 recognized tribes and 18 subtribes. A dichotomous key to the tribes is provided. All names in the taxonomic treatments are hyperlinked to online resources for individual taxa which are supported by a comprehensive database for Deltocephalinae compiled using the taxonomic database software package 3I. The online functionality includes an interactive key to tribes and subtribes and advanced database searching options. Each taxon (subspecies through subfamily) has a unique taxon webpage providing nomenclatural information, lists of included taxa, an automated description (if available), images (if available), distributional information, bibliographic references and links to outside resources.

Deltocephalinae, a highly diverse and economically important subfamily of leafhoppers, contains over 6200 species and 36 tribes distributed worldwide in habitats ranging from xeric grasslands and shrublands to tropical rainforests. Recent morphological and molecular phylogenetic analyses of Cicadellidae and a morphology‐based analysis of Deltocephalinae and related subfamilies indicated that several previously recognized cicadellid subfamilies are closely related to or derived from within Deltocephalinae, but these analyses did not provide a comprehensive or well‐supported hypothesis of the phylogeny of Deltocephalinae s.l. due to either low taxon sampling or low branch support. Here, taxon sampling was increased to include members of most family‐group taxa of Deltocephalinae and molecular data (∼2800 bp 28S rDNA and ∼350 bp histone H3) were added to improve the phylogenetic estimate. Five putative outgroup taxa were included, and parsimony and Bayesian analyses of the combined molecular and morphological (119 characters) data and maximum likelihood analyses of the 28S data showed strong support for the monophyly of Deltocephalinae as defined here. Branches near the base of the tree and towards the tips were longer and better supported than many of the shorter internal branches. Similar to a previous morphological phylogenetic analysis of Deltocephalinae, all of the grass‐ and sedge‐specializing tribes were recovered in one common clade, with a few apparent reversals to nongrass feeding. Although support for this clade was low and requires further testing, the results suggest that grass/sedge specialization is a phylogenetically conservative trait within Deltocephalinae. The history of the classification of Deltocephalinae and related subfamilies is reviewed, and based on the results of the phylogenetic analyses presented here, a revised family‐group taxonomic classification is proposed. In addition to subfamilies that were recently included in Deltocephalinae, the following are considered junior synonyms of Deltocephalinae: Acostemminae syn.n., Arrugadinae syn.n., Drakensbergeninae syn.n., Mukariinae syn.n. and Stegelytrinae syn.n. The morphological characters supporting this interpretation of Deltocephalinae are provided and discussed, and a description of the subfamily is provided. A new tribe, Faltalini tribe n. (11 genera, 31 species) is described, and Magnentiini placement n. and Paraphrodini placement n. are transferred to Deltocephalinae from Nioniinae and Aphrodinae, respectively. New placements of genera include: Twiningia Ball and Eusama Oman (Athysanini: Platymetopiina), placement n.; Cerrillus Oman (Athysanini), placement n.; Scaphotettix Matsumura and Agrica Strand (Mukariini), placement n.; Loralia Evans and Phlogotettix Ribaut (Deltocephalinae, unplaced to tribe), placement n. The recognition of Scaphoideini Oman 1943 as a nomen nudum results in the following placements: Acunasus DeLong, Cantura Oman, Danbara Oman, Osbornellus Ball, Prescottia Ball, Scaphodhara Viraktamath & Mohan, Scaphoideus Uhl...

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We analysed a phylogenomic dataset comprising 730 terminal taxa and >160,000 nucleotide positions obtained using anchored hybrid enrichment of genomic DNA for a sample of deltocephaline leafhoppers and outgroups. Maximum likelihood analyses of concatenated nucleotide and amino acid sequences as well as coalescent gene tree analysis, yielded well-resolved phylogenetic estimates that were highly congruent with most branches receiving maximum support. Some topological incongruence occurs among the trees resulting from different analyses, mainly distributed among very short branches at intermediate levels in the phylogeny, pertaining to relationships among some tribes and multi-tribe lineages restricted to particular continents. Coalescent gene tree analysis revealed extensive gene tree conflict at these nodes, suggesting that certain relationships may remain difficult to resolve consistently even with genome-scale datasets and dense taxon sampling. Ancestral character state reconstruction of feeding preference indicates that grass specialization has been acquired three or fewer times in some highly diverse but relatively derived lineages. Molecular divergence time estimation suggests that the earliest divergences in the subfamily occurred during the Cretaceous but that most modern tribes did not appear until after the Cretaceous-Palaeogene boundary and that grass specialist lineages generally diversified and spread at the same time as grasslands were becoming widespread globally. These analyses also show a high level of global biogeographic structure, with several large lineages of primarily arboreal deltocephalines restricted to particular regions or continents and long-distance dispersal among continents occurring primarily among grass-specialist lineages. The results represent a major improvement over previous analyses of this diverse subfamily, which were based on 152 or fewer taxa and data from morphology and partial sequences of two genes.