Ectoparasitic thrips affect the behaviour of their aetalionid treehopper hosts

Aulacothrips dictyotus Hood, 1952 (Thysanoptera: Heterothripidae) is a highly specific ectoparasite, which infests nymphs and adults of Aetalion reticulatum (Linnaeus, 1758) (Hemiptera: Aetalionidae) in South America. However, nothing is known about the consequences of this remarkable interaction to the hemipterans, which also exhibit mutualistic associations with ants. In this study, we test the hypothesis that Au. dictyotus directly affects Ae. reticulatum behaviour by comparing ethograms of thrips‐infected and uninfected aetalionids. An analysis of 15 behavioural acts showed significant differences in the behaviour of Ae. reticulatum between these two experimental groups. Hemipterans exhibited dramatic changes in behaviour under Au. dictyotus presence, and the frequencies of some behaviours related to locomotion were statistically higher in individuals with thrips, as well as kicking movements using the hind legs. Moreover, infected aetalionids showed higher frequencies of grooming behaviour, which seems to have some efficacy in detaching Au. dictyotus. We demonstrated that thrips presence disturb host foraging behaviour and induces unusual behavioural acts that are likely to be very costly to hosts. Our results suggest that thrips parasitism constitutes an important selective force for hemipterans and that its effects can influence host individuals, the aggregation and potentially the mutualistic interaction with ants.