Aciurina opaca is so rarely collected that little can be stated about its biology. Each of two specimens collected were reared from galls on C. nauseosus. A single female emerged from a gall collected on 18 March 1974 and a single male was reared from a gall collected on 21 April 1974. The flies issued from stem swellings that appeared identical to those described for Valentibulla spp. (Wangberg, 1978). It is not known how the apparent gall-forming habit of A. opaca differs from Valentibulla spp.