The effect of selected single compounds from essential oils of the groups monoterpenes (carvacrol, thymol, linalool, 4-terpineol), phenylpropanoids (eugenol) and salicylates (methyl salicylate, salicylaldehyde) was tested on two polyphagous pest species, Frankliniella occidentalis Pergande and Thrips tabaci Lindeman (Thysanoptera: Thripidae). A model catalogue of behavioural patterns was developed for both thrips species and the behavioural changes induced by exposure to single chemical compounds, applied onto host plants, described. Bean (Phaseolus vulgaris L.) and cucumber (Cucumis sativus L.) were used in experiments with F. occidentalis, leek (Allium porrum L.) and cucumber for T. tabaci. The behavioural changes, i.e. occurrence, duration and frequency of single behavioural sequences, were qualitatively and quantitatively analysed. Furthermore, take-off rates in five-minute short term experiments, settling time in three hour choice tests and the reduction of oviposition and feeding damage in 24 hour no-choice experiments were evaluated. The chemicals methyl salicylate and carvacrol appeared specifically effective against F. occidentalis as well as linalool and eugenol against T. tabaci. The settling time of thrips in choice tests was reduced and their exploration activity generally increased together with reduced oviposition behaviour and feeding damage. These behavioural manipulations may be exploited in various pest management strategies. However, the intensity of the effects varied between plant species. In most parts of this work the Observer (Noldus), a program for computing behavioural data, was used for collecting and analysing data.