Locomotor behavior of flightless Harmonia axyridis Pallas (Col., Coccinellidae)

To improve the efficiency of the lady beetle H. axyridis as a biological co ntrol agent against aphids, a flightless population was obtained by feeding adults with a mutagen and selecting their progeny for nonflying but otherw ise morphologically normal individuals. These flightless adults attempted t o fly but immediately fell. They softened their fall by opening their elytr ae and wings. The inability to fly could result from change in their flying behavior compared to control adults. The flight duration was very much sho rter, and the wing beat frequency and, more particularly, the amplitude of the wing beats were clearly lower. More time was spent in the other compone nts of the flight behavior such as wing rotation, wing immobility, and wing folding. The sequence of these patterns differed slightly, due mainly to c hange in their frequency. The locomotor behavior was not modified by the mu tation, which affected only the wing muscles. Searching behavior of mutant adults differed from that of control adults only in that they took longer t o encounter and ingest aphids. Nevertheless, the larval growth and reproduc tive rate remained unchanged. The behavioral and biological features of the se flightless adults indicate that it should be possible to use them in bio logical control programs.