Department of Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America.
PLoS One. 2013 Apr 22;8(4):e62051. doi: 10.1371/journal.pone.0062051. Print 2013.
Male parasitic wasps attract females with a courtship song produced by rapid wing fanning. Songs have been described for several parasitic wasp species; however, beyond association with wing fanning, the mechanism of sound generation has not been examined. We characterized the male courtship song of Cotesia congregata (Hymenoptera: Braconidae) and investigated the biomechanics of sound production.
Courtship songs were recorded using high-speed videography (2,000 fps) and audio recordings. The song consists of a long duration amplitude-modulated "buzz" followed by a series of pulsatile higher amplitude "boings," each decaying into a terminal buzz followed by a short inter-boing pause while wings are stationary. Boings have higher amplitude and lower frequency than buzz components. The lower frequency of the boing sound is due to greater wing displacement. The power spectrum is a harmonic series dominated by wing repetition rate ∼220 Hz, but the sound waveform indicates a higher frequency resonance ∼5 kHz. Sound is not generated by the wings contacting each other, the substrate, or the abdomen. The abdomen is elevated during the first several wing cycles of the boing, but its position is unrelated to sound amplitude. Unlike most sounds generated by volume velocity, the boing is generated at the termination of the wing down stroke when displacement is maximal and wing velocity is zero. Calculation indicates a low Reynolds number of ∼1000.
Acoustic pressure is proportional to velocity for typical sound sources. Our finding that the boing sound was generated at maximal wing displacement coincident with cessation of wing motion indicates that it is caused by acceleration of the wing tips, consistent with a dipole source. The low Reynolds number requires a high wing flap rate for flight and predisposes wings of small insects for sound production.
雄性寄生蜂通过快速扇动翅膀来吸引雌性，发出求偶声。已经描述了几种寄生蜂的歌曲；然而，除了与翅膀拍打有关之外，声音产生的机制尚未被研究。我们对寄生蜂 Cotesia congregata（膜翅目：Braconidae）的雄性求偶歌曲进行了特征描述，并研究了声音产生的生物力学。
使用高速录像（2000fps）和音频记录来记录求偶歌曲。歌曲由长持续时间的调制“嗡嗡”声组成，随后是一系列脉动的高振幅“砰砰”声，每个“砰砰”声衰减为终端嗡嗡声，然后在翅膀静止时短暂的终端“砰砰”声之间暂停。“砰砰”声的振幅比“嗡嗡”声高，频率比“嗡嗡”声低。“砰砰”声的低频是由于翅膀的位移更大。功率谱是一个以翅膀重复率约 220Hz 为主的谐波系列，但声音波形表明存在约 5kHz 的更高频率共振。声音不是由翅膀相互接触、基底或腹部产生的。在“砰砰”声的前几个翅膀循环中，腹部会升高，但它的位置与声音振幅无关。与大多数由体积速度产生的声音不同，“砰砰”声是在翅膀向下挥动的最后几个翅膀循环中产生的，此时位移最大且翅膀速度为零。计算表明雷诺数约为 1000。
典型声源的声压与速度成正比。我们发现，“砰砰”声是在翅膀最大位移与翅膀运动停止同时产生的，这表明它是由翼尖的加速度引起的，与偶极子声源一致。低雷诺数要求翅膀拍打率高以进行飞行，并使小昆虫的翅膀易于产生声音。
