Certain novel N-(heteroarylalkyl)alkanediamine derivatives have provided unexpected insecticidal and acaricidal activity. These compounds are represented by formula I: wherein Ar, a, b, c, T, W, Y, R, Rf, Rg, Rh, Ri, Rj, Rk, Rm, Rn, and R7 are fully described herein. In addition, compositions comprising an insecticidally effective amount of at least one compound of formula I, and optionally, an effective amount of at least one of a second compound, with at least one insecticidally compatible carrier are also disclosed; along with methods of controlling insects comprising applying said compositions to a locus where insects are present or are expected to be present.