Investigation of the antennal surfaces in 4 species of the family Ecnomidae ( Ecnomus insularis , E. maheensis , E. jethet and E. tenellus ) has revealed the presence of antennal structures including long trichoid, curved trichoid, mushroom-like pseudoplacoid, basiconic, styloconic, and chaetoid sensilla, as well as the Böhm’s bristles. Average numbers and diversity of the sensilla decrease toward the antennal apex. Interpopulational differences in the size and numbers of sensilla, mostly the curved trichoid ones, were found for the first time in insects in the widespread species Ecnomus tenellus. Quantitative differences of sensilla found in every studied species are probably adaptive. Evolutional significance of the revealed divergence is discussed.