02528nas a2200217   4500008004100000245010300041210006900144520177600213653002701989653002202016653001602038653001202054653002102066653001202087653001902099100001702118700001902135700001902154700001702173856012002190       2011                        eng d00aWhistling in caterpillars (Amorpha juglandis, Bombycoidea): sound-producing mechanism and function0 aWhistling in caterpillars Amorpha juglandis Bombycoidea soundpro3 a<p>Caterpillar defenses have been researched extensively, and, although most studies focus on visually communicated signals, little is known about the role that sounds play in defense. We report on whistling, a novel form of sound production for caterpillars and rare for insects in general. The North American walnut sphinx (Amorpha juglandis) produces whistle &lsquo;trains&rsquo; ranging from 44 to 2060ms in duration and comprising one to eight whistles. Sounds were categorized into three types: broadband, pure whistles and multi-harmonic plus broadband, with mean dominant frequencies at 15kHz, 9kHz and 22kHz, respectively. The mechanism of sound production was determined by selectively obstructing abdominal spiracles, monitoring air flow at different spiracles using a laser vibrometer and recording body movements associated with sound production using high-speed video. Contractions of the anterior body segments always accompanied sound production, forcing air through a pair of enlarged spiracles on the eighth abdominal segment. We tested the hypothesis that sounds function in defense using simulated attacks with blunt forceps and natural attacks with an avian predator &ndash; the yellow warbler (Dendroica petechia). In simulated attacks, 94% of caterpillars responded with whistle trains that were frequently accompanied by directed thrashing but no obvious chemical defense. In predator trials, all birds readily attacked the caterpillar, eliciting whistle trains each time. Birds responded to whistling by hesitating, jumping back or diving away from the sound source. We conclude that caterpillar whistles are defensive and propose<br />
	that they function specifically as acoustic &lsquo;eye spots&rsquo; to startle predators.</p>
10aacoustic communication10aAmorpha juglandis10acaterpillar10adefense10asound production10awhistle10ayellow warbler1 aBura, V., L.1 aRohwer, V., G.1 aMartin, P., R.1 aYack, J., E.  uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.046805https://syndication.highwire.org/content/doi/10.1242/jeb.046805