Cocroft R B, Tieu T D, Hoy R R, Miles R N
Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
J Comp Physiol A. 2000 Jul-Aug;186(7-8):695-705. doi: 10.1007/s003590000123.
The use of substrate vibrations in communication and predator-prey interactions is widespread in arthropods. In many contexts, localization of the vibration source plays an important role. For small species on solid substrates, time and amplitude differences between receptors in different legs may be extremely small, and the mechanisms of vibration localization are unclear. Here we ask whether directional information is contained in the mechanical response of an insect's body to substrate vibration. Our study species was a membracid treehopper (Umbonia crassicornis) that communicates using bending waves in plant stems. We used a bending-wave simulator that allows precise control of the frequency, intensity and direction of the vibrational stimulus. With laser-Doppler vibrometry, we measured points on the substrate and on the insect's thorax and middle leg. Transfer functions showing the response of the body relative to the substrate revealed resonance at lower frequencies and attenuation at higher frequencies. There were two modes of vibration along the body's long axis, a translational and a rotational mode. Furthermore, the transfer functions measured on the body differed substantially depending on whether the stimulus originated in front of or behind the insect. Directional information is thus available in the mechanical response of the body of these insects to substrate vibration. These results suggest a vibration localization mechanism that could function at very small spatial scales.
在节肢动物中，利用底物振动进行通讯和捕食者 - 猎物相互作用的现象十分普遍。在许多情况下，振动源的定位起着重要作用。对于在固体底物上的小型物种而言，不同腿部感受器之间的时间和振幅差异可能极小，而振动定位机制尚不清楚。在此，我们探究昆虫身体对底物振动的机械响应中是否包含方向信息。我们的研究对象是一种角蝉科树蝉（Umbonia crassicornis），它利用植物茎干中的弯曲波进行通讯。我们使用了一个弯曲波模拟器，可精确控制振动刺激的频率、强度和方向。通过激光多普勒测振仪，我们测量了底物以及昆虫胸部和中腿上的点。显示身体相对于底物响应的传递函数表明，在较低频率处存在共振，在较高频率处出现衰减。沿着身体长轴有两种振动模式，一种是平移模式，一种是旋转模式。此外，根据刺激源自昆虫前方还是后方，在身体上测量的传递函数有很大差异。因此，这些昆虫身体对底物振动的机械响应中存在方向信息。这些结果表明了一种可能在非常小的空间尺度上起作用的振动定位机制。
