Topical application of a single dose (10µl/tick or egg batch) of different concentrations of abamectin (an avermectin) has lethal and biological effects on the engorged mated adult female, immatures and egg of Argas (Persicargas) arboreus that induced 100% mortality at 25,15 and 10 ppm, respectively. Abamectin treatment at lower concentrations of 1-10 ppm interfered with the female reproduction, nymphal and egg development.
     Abamectin topical (3-10 ppm) application on mated engorged adult female A. (P.) arboreus at different intervals of its reproductive cycle reduced fecundity and fertility of the female, prolonged its preoviposition, oviposition and the egg incubation periods. The effects were most prominent during vitellogenesis and the least at the start of oviposition.
     Abamectin treatment of the newly moulted fed 2^nd nymphal instar, delayed its moulting and of the resulted 3^rd instar and reduced adult emergence. The treatment caused paralysis and various deformities (15.6-28.6%) as missing legs at the coxal level, changes in colour and failure to moult or to detach the old exuvia in the resulted 3^rd nymphal instar.
     Egg batch treatment by dipping the freshly deposited eggs for 20 seconds in an aqueous solution of 1-5 ppm abamectin was more effective in reducing normal hatching, increasing unhatching and total inhibition of egg development than topical treatment. However, both methods of treatment similarly prolonged the egg incubation periods and caused abnormal hatching, malformations, and anomalies in the eggs and embryos