The larvicidal bioassays were conducted according to standard
WHO techniques (2005). Bioassays were conducted in 250-ml
plastic cups. An aliquot (1 ml) of essential oil dissolved in
soybean oil (1, 5, and 10 %) was added to 99 ml of distilled water. Ten immature stages (third or fourth instar) of Ae.aegypti and An. dirus were transferred to the test medium. All
larvae were exposed until pupation, and mortality was recorded
at 24-h intervals. Dead larvae, pupae, exuviae, and adults were
removed and placed in labeled plastic vials containing 70 %
ethanol The morphological aberrations of the dead mosquitoes
were determined using a stereomicroscope. Dead specimens
were grouped and modified according to those described by
Ratanatham et al and Yodbutra et al. They were
categorized into the following eight groups