Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Until now, Aulacothrips dictyotus Hood (Heterothripidae) is the only known thrips to exhibit an ectoparasitic way of life, infesting nymphs and adults of the aetalionid treehopperAetalion reticulatum. However, recent observations in Brazilian Cerrado showed another Aulacothrips species infecting several honeydew-producing hemipteran species, mainly membracid treehoppers. Both parasitic species are usually found within a complex multitrophic system, which involves ant hemipteran mutualism, a host plant and associated insect herbivores. In this paper, we present new data about ectoparasitism in Thysanoptera, describe Aulacothrips minor sp. nov. as well as males of A. dictyotus, and provide identification keys for adults and larvae of both species. Records of the infected Hemiptera species are given, including their host plants and associated tending-ants. Our results suggest A. dictyotus to be a host specific thrips restricted to A. reticulation. In contrast, A. minor has a wide range of hosts, attacking 15 hemipteran species, all of them showing a gregarious and myrmecophilous habit. Differences observed in morphology, host use and life history strategies between the Aulacothrips species are also discussed. (C) 2010 Elsevier GmbH. All rights reserved.24941732209221Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPq [143326/2008-2, 140183/2006-0]FAPESP [08/54058-1]