7 Auditory Systems in Insects

Evolution has endowed insects with an extraordinary capacity for miniaturization. Virtually all aspects of insect biology convey the sense of successfully uniting form and function in exquisitely small, diverse, and sophisticated motor, sensory, and metabolic systems (Grimaldi and Engel 2005). The ability of insects to fly in an efficient and controlled manner well illustrates how, through evolution by natural selection, they adapted to solve what we consider serious problems of engineering. Insects are little marvels of “evolutionary engineering.” The seemingly boundless ingenuity and creativity of the process of evolutionary adaptation are also reflected in the sensory systems of insects. As we try to make clear in this chapter, hearing in insects is a sophisticated process; understanding its fundamental mechanisms and trying to understand its evolution present many challenges but are likely to be very rewarding. Perhaps because insects are so small, their ears have generally been considered to be simple compared to those of vertebrates. Anatomically, they may be simpler, but their capacity for sound reception and processing turns out to be remarkably elaborate (for reviews, see Fullard and Yack 1993; Hoy 1998; Robert and Gopfert 2002; Robert 2005; Hedwig 2006; Gopfert and Robert 2007). The ears of insects can be as sensitive and acute as their vertebrate counterparts (Webster et al. 1992; Hoy 1998). Indeed, in some cases their feats of detection surpass the capabilities of vertebrates (Robert and Gopfert 2002). For example, the ultrafast ears of the parasitoid fly Ormia ochracea can distinguish time differences in the arrival...