02528nas a2200217 4500008004100000245010300041210006900144520177600213653002701989653002202016653001602038653001202054653002102066653001202087653001902099100001702118700001902135700001902154700001702173856012002190 2011 eng d00aWhistling in caterpillars (Amorpha juglandis, Bombycoidea): sound-producing mechanism and function0 aWhistling in caterpillars Amorpha juglandis Bombycoidea soundpro3 a

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 ‘trains’ 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 – 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
that they function specifically as acoustic ‘eye spots’ to startle predators.

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.04680502213nas a2200133 4500008004100000245011000041210006900151520166500220100001801885700002401903700001501927700001701942856012001959 2009 eng d00aAuditory mechanics and sensitivity in the tropical butterfly Morpho peleides (Papilionoidea, Nymphalidae)0 aAuditory mechanics and sensitivity in the tropical butterfly Mor3 a

The ears of insects exhibit a broad functional diversity with the ability to detect sounds across a wide range of frequencies and intensities. In tympanal ears, the membrane is a crucial step in the transduction of the acoustic stimulus into a neural signal. The tropical butterfly Morpho peleides has an oval-shaped membrane at the base of the forewing with an unusual dome in the middle of the structure. We are testing the hypothesis that this unconventional anatomical arrangement determines the mechanical tuning properties of this butterfly ear. Using microscanning laser Doppler vibrometry to measure the vibrational characteristics of this novel tympanum, the membrane was found to vibrate in two distinct modes, depending on the frequency range: at lower frequencies (1–5 kHz) the vibration was focused at the proximal half of the posterior side of the outer membrane, while at higher frequencies (5–20 kHz) the entire membrane contributed to the vibration. The maximum deflection points of the two vibrational modes correspond to the locations of the associated chordotonal organs, suggesting that M. peleides has the capacity for frequency partitioning because of the different vibrational properties of the two membrane components. Extracellular nerve recordings confirm that the innervating chordotonal organs respond to the same frequency range of 1–20 kHz, and are most sensitive between 2 and 4 kHz, although distinct frequency discrimination was not observed. We suggest that this remarkable variation in structure is associated with function that provides a selective advantage, particularly in predator detection.

1 aLucas, K., M.1 aWindmill, J., F. C.1 aRobert, D.1 aYack, J., E. uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.032425https://syndication.highwire.org/content/doi/10.1242/jeb.032425