Falciform, fully-formed oregano leaves (Origanum vulgare L.) and lavender leaves and flowers (Lavandula officinalis L.) were collected in the geographical area of Mar del Plata (38° 00′ 24.17” S-57° 33′ 55.89” W) during July 2011. Plant specimens were classified and stored in the herbarium of vascular plants (AL 17 and PV 97, Arthropods laboratory, Faculty of Sciences, Universidad Nacional de Mar del Plata). Essential oils were extracted by hydrodistillation using a Clevenger type apparatus according to the method reported elsewhere ( Gende et al., 2010) from freshly dried plant material