. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INNOVATIVE AUDITORY MICROMECHANICS the anterior thorax just above the first pair of legs, which are directly below the fly's neck (Robert ft 1992) (Fig. 1 A). The ears of the fly are endowed with two thin tympanal membranes, the eardrums, that are set very close together across the midline of the animal. In fact, while the tympanal membranes together span about mm in width, the mechanoreceptive sensory organs are separated from each other by only 520 /im (Robert et 1994) (Fig. 1A). As expected from the fly's sm
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INNOVATIVE AUDITORY MICROMECHANICS the anterior thorax just above the first pair of legs, which are directly below the fly's neck (Robert ft 1992) (Fig. 1 A). The ears of the fly are endowed with two thin tympanal membranes, the eardrums, that are set very close together across the midline of the animal. In fact, while the tympanal membranes together span about mm in width, the mechanoreceptive sensory organs are separated from each other by only 520 /im (Robert et 1994) (Fig. 1A). As expected from the fly's small size and the resulting minute interaural distance, the largest interaural time difference (ITD) generated by a passing sound wave does not exceed 2 /is (Robert et al., 1996). In the best possible case, for an azimuthal angle of inci- dence of 90° off the longitudinal axis of the animal, the ITD was measured with probe microphones to be /is (SD: /is. n = 10) (Fig. IB). Such time difference is clearly much too small to be encoded by the nervous Contralateral. -90 -60 -40 -20 0 20 40 60 Angle of Incidence [degrees] Figure 1. Auditory anatomy and temporal acoustic cues. (A) The auditory organs of the parasitoid fly Ormia ochracea are located on the anterior thorax, between the first pair of legs (L) and the neck (N). The tympanal membranes (TM) are adjacent to each other and set close to- gether by the midline of the animal (vertical dashed line). Providing a connection between the two TMs across the midline, the intertympanal bridge is made of thicker cuticle than TMs and has the shape of a coat hanger. Two depressions at both ends of the intertympanal bridge indicate the insertion point of the sensory organs (arrows). Arrows also point to the interaural distance. (B) Interaural time difference (ITD) as a function of the angle of incidence of the sound stimulus. Right ordinate: ITDs calculated for humans (ear separation of 170 mm). Left ordinate: ITDs at the fly's e
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
