Accepted by A.-P. Liang: 15 Jan. 2019; published: 5 Mar. 2019 ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Copyright © 2019 Magnolia Press Zootaxa 4564 (1): 137–172 https://www.mapress.com/j/zt/ Article 137 https://doi.org/10.11646/zootaxa.4564.1.5 http://zoobank.org/urn:lsid:zoobank.org:pub:5EA3EB07-F3FD-4F05-9478-EAE0AA797CDE Comparative morphology of female gonapophyses IX in Delphacidae (Hemiptera: Auchenorrhyncha: Fulgoromorpha) with key to tribes ADAM M. WALLNER 1,3 & CHARLES R. BARTLETT 2 1 United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine, 6302 NW 36 th St, Miami, FL 33122, USA. 2 University of Delaware, Department of Entomology and Wildlife Ecology, 531 S. College Ave., 250 Townsend Hall, Newark, DE 19716, USA. E-mail: Bartlett@udel.edu 3 Corresponding author. E-mail: adam.m.wallner@aphis.usda.gov Abstract Diagnoses for delphacid species rely on male genitalia, with female structures rarely considered. In this study, we exam- ined gonapophyses IX from 36 exemplar species, representing all 14 tribes of Delphacidae. From these 36 species, we found 53 potential synapomorphies. We present a key to delphacid tribes that integrates gonapophyses IX features. We hypothesize that the basal delphacids, the Asiracinae, have teeth concentrated at the apex to make short incisions into soft plant tissue. In Vizcayinae, these teeth are greatly reduced, extending past the apex, and may function to pierce host tissue. In Plesiodelphacinae, these teeth are increased in size and number, potentially to function as a saw. In Kelisiinae, teeth size is reduced, while teeth frequency is increased subapically. Finally, in the Stenocraninae and Delphacinae, the most derived lineages, an increase in tooth size and shape may have developed to cut into graminoid hosts with high concen- trations of silicate. Key words: Fulgoroidea, plant associations, systematics Introduction Gonapophyses IX (i.e., the 2 nd valvula) of the hemipteran ovipositor has been an important reservoir of characters in species descriptions, taxonomic keys, and in elucidating evolutionary relationships of lineages among subfamily-, tribal- (Deitz 1975, Zahniser & Dietrich 2013, Paladini et al. 2015, Konstantinov & Knyshov 2015), and species-levels (Balduf 1933, 1934; Zahniser 2005, Domahovski et al. 2015). Features utilized include the number and location of teeth along the inner, lateral margin (Deitz 1975), vestiture (e.g., reticulating pattern, spine baring scales) (Zahniser 2005, Hummel et al. 2006, Zahniser & Dietrich 2013) and shape of the gonapophyses and its apex (Domahovski et al. 2015). Within Fulgoroidea (Hemiptera: Auchenorrhyncha), gonapophyses IX is often overlooked. Few studies have examined these structures for systematic purposes for defining putative groups within Delphacidae (Müller 1942, Okada 1977, Ossiannilsson 1978, Heady & Wilson 1990, Roxana & de Remes Lenicov 2001). While other studies described related structures, such as the pregenital sternite among Delphacidae, Flatidae, Issidae, and Nogodinidae (Doering 1932, 1938; Doering & Shepherd 1946, Kramer 1976, Asche 1990, Świerczweski & Stroiński 2015). Nevertheless, these structures were not used in separating species. Some research has explored internal female structures (e.g., Bourgoin & Huang 1991, Wang et al. 2009) and have proposed diagnostic features, for example, the sclerotized walls of the female ‘edeagal duct’ in separating Kelisia species (Remane & Guglielmino 2002). At the family level, a phylogenetic progression has been proposed among planthoppers for ovipositor form and function (e.g., Asche 1988b, Bourgoin 1993, Wilson et al. 1994). Basal planthoppers (viz. Delphacidae and Cixiidae) possess a sword-shaped ‘orthopteroid’ ovipositor (with a piercing, saw-like structure) to insert eggs in plant tissue, whereas more derived lineages possess variations on a ‘fulgoroid ovipositor,’ with piercing, excavating, or raking structures that function to cement or cover eggs, rather than inserting them into plant tissue. It