Abstract Adults of the rose chafer were collected from grape blossom buds in a sandy area near North Kingsville, Ohio, just prior to bloom. These insects were brought to O.A.R.D.C. to test their susceptibility to a broad range of insecticides. They were held 24 hr at the holding conditions indicated below, prior to being treated. Methoxychlor had given poor results in the area of collection. Stock solutions (1%) of all materials tested were prepared from technical grade materials using a mixture of acetone and olive o i l , 19:1 (vol/vol), as the solvent. Two replicates of 10 beetles each, selected at random, were anesthetized with ether and placed on filter paper in 9-cm glass petri dishes. Each replicate was sprayed with 5 ml of the insecticides at one of the concentrations in a Potter spray tower. Checks consisted of 2 sets of 10 beetles each sprayed with the solvent. Treated beetles were removed from petri dishes and placed in paper cups with a moist wick of 5% honey-water and covered with a glass petri dish and held at 24° t 1,5°C and 6 0% RH. Treatments were made on June 17 and mortality readings were made 24 hours later.