The nymph and adult H. longicornis ticks (Sungwhanstrain, Korea) used in the present study originated fromthe Parasitology and Insect Disease Research Laboratory,Animal and Plant Quarantine Agency, Korea, and were atthe same developmental stage. The ticks were reared at28 ± 3◦C and at 75 ± 5% relative humidity.Twenty-four male New Zealand white rabbits, rangingfrom 2.5 to 3.0 kg in body weight, were used as hosts andtreated with each of the avermectins.Two days before the initiation of avermectin treat-ments, 12 rabbits were each infested with 150 H. longicornisnymphs that were approximately 20 days old, and 12rabbits were each infested with 10 H. longicornis malesand 60 H. longicornis females of approximately 30 days old.Rabbits were then placed in individual cages. Three rabbitsinfested with nymphs and three rabbits infested withadults were randomly allocated to each of four treatmentgroups. On day zero, rabbits were weighed individuallywhen prior to treatment. Animals in the three treatmentgroups were treated with ivermectin 1% (Bayer Korea,Korea), doramectin 1% (Pfizer Korea, Korea), or abamectin1% (Virbac Korea, Korea); animals in the control group werenot treated. Each animal in the treatment groups received asingle subcutaneous injection of each avermectin at a doseof 200 g/kg live weight. The engorged ticks that droppedfrom the animals were collected.On days 3, 7, and 14 after treatment, up to 20 engorgednymphs or 10 engorged females were randomly collectedfrom each rabbit (whenever possible) and weighed. Onday 14 after treatment, ovary development in femaleticks was quantified by expressing the ovary weight asa % of the body weight of engorged female ticks (Lunkeand Kaufman, 1992). Ten female ticks from each animalwere randomly selected and flooded with modified Hank’smedium, the dorsal cuticle and gut were removed, andthe ovaries and oviducts were exposed. The ovaries werethen gently blotted and weighed. The engorged nymphswere observed daily until day 30 under dim red light, todetermine whether they had moulted, according to Chiltonet al. (2000).Data from the control and treatment groups werecompared statistically by using an analysis of variance(ANOVA). The p value