this study aimed to analyze the chemical composition and to evaluate the essential oil activity of lantana camara and lantana montevidensis against r. microplus larvae and engorged females. analysis of essential oils by gc and gc/ms allowed the identification of 34 constituents. l. camara oil was mainly composed of bicyclogermacrene, isocaryophyllene, valencene and germacrene-d. l. montevidensis oil was mainly composed of -caryophyllene, germacrene-d and bicyclogermacrene. acaricidal activity of the essential oils against r. microplus was evaluated by larval sensitivity and tests using engorged females. l. camara and l. montevidensis essential oils possessed high activity against engorged females with lc50 of 2.9 and 3.3 mg/ml, respectively. acaricidal activity against r. microplus was moderate with lc50 of 8.8 and 9.2 mg/ml for the l. camara and l. montevidensis essential oils, respectively. lc50 values indicated greater oil activity against engorged females in relation to larvae, with a relevant acaricidal activity against r. microplus.