Certain novel N-alkanediamine derivatives have provided unexpected insecticidal and acaricidal activity. A photodetector device comprises a local light emitting unit for generating a local light in temporally unstable interference condition with a light to be detected and a photoelectric conversion unit for generating beat signals between the local light and the light to be detected by photoelectric conversion. The incentive rewards system administering an incentive rewards program determines whether a customer of a business participating in the incentive rewards program is eligible for a loyalty-based incentive redeemable at the business.