The three EOs and the R-(+)-limonene were employed forfurther studying their biological activity on mosquito larvae.Thus, the concentration required to kill 50 % of the larvae within 24 h (LC50 value), which had already been determined from larval bioassays, was chosen as sublethal dose of each tested material. Batches of 20 late third- and early fourth-instar larvae were placed in beakers with 2 % (v/v)aqueous solution of DMSO (98 ml of tap water plus 2 ml ofDMSO) and exposed to the LC50 dose of each tested substance.Twenty-four hours after treatment, dead larvae were counted and only alive ones were transferred, via a small strainer, to beakers covered with netting and filled with 100 ml tap water. Larvae were provided with a small amount of powdered fish food at a concentration of 10 mgl−1 at 2-
day intervals until pupation (WHO 2005). The number of pupae formed and adults emerged were counted daily. The untreated control was prepared using 2 % aqueous solution of DMSO (100 ml in total) and containing 20 late third- and early fourth-instar larvae, which were transferred, 24 h later,to beakers with clean tap water and the food regime. For each substance and control, five replicates were performed (n05) at the same time. For all larvicidal bioassays, beakers with larvae were placed at 25±2 °C, 80±2 % relative humidity and photoperiod of 16:8-h L/D.The resulted alive adults were collected daily from each beaker and transferred separately to translucent plastic containers with netting and free access to 10 % sucrose solution.Adult survivorship was recorded daily for 20 days andreferenced to the survival of untreated (control) mosquitoes.