Abstract The new genus Maxiclavella is proposed to accommodate Clavella simplex Castro Romero and Baeza Kuroki, 1985, which differs from Clavella species, including long and narrow cephalothorax, small bulla, and simple armature of the antenna and antennule. Praeclavella nasalis, new genus and species, was found parasitizing the olfactory sacs of Isacia conceptionis. Praeclavella nasalis could be differentiated from other Clavella species by a biramous antenna with an exopod shorter than the endopod, the base of the cephalothorax with a large lobular and suborbicular projection on each side, a suborbicular bulla, mandibles without secondary teeth, and a suboval male body type. Males of both genera fit well in the Clavella-clade male type, although they differ from each other in many aspects, mainly in the position of the buccal area, which is oriented ventrally in Maxiclavella and distally in Praeclavella nasalis, and in a genital process, which is present in the latter and absent in the former. Genetic distances of mtDNA COI and 28S rDNA supported the validity of the two new genera parasitizing the same host, I. conceptionis. Also Clavella-branch (Clavellinae Wilson), a key based genera on female specimens is presented.

RESUMEN Se encontraron nematodos de la familia Mermithidae parasitando ninfas y adultos de Hortensia similis (Auchenorryncha: Cicadellidae). Los especímenes hospedadores fueron recolectados en malezas asociadas a huertos de cítricos ubicados en la provincia de Corrientes, Argentina, durante un estudio de biodiversidad en 2015. Hasta donde sabemos, este es el primer ejemplo de chicharritas parasitadas por un mermítido en Sudamérica.

ABSTRACT Nematodes of the family Mermithidae were found parasitizing adults and nymphs of the species Hortensia similis (Auchenorryncha: Cicadellidae). The host specimens were collected from weeds associated to citrus orchards located in Corrientes, Argentinean province, during a biodiversity study in 2015. As far as we know, this is the first South American example of leafhoppers parasitized by mermithids.