振動的避難所：糞鏈上的鱗翅目幼蟲是否可藉由振動以提高防禦螞蟻的效率？

Abstract

本研究首次發現鱗翅目 (Lepidoptera) 幼蟲在糞鏈 (frass chain) 頂端的振動行為，以及證明「振動」可大幅增加幼蟲的存活率。獵物如何在捕食中存活下來是很重要的課題，經選汰下的獵物已發展出多樣化的防禦策略。建造糞鏈是鱗翅目幼蟲行為防禦的一種。糞鏈與葉主脈共同組成幼蟲停棲的「蟲巢」。過去研究已證明幼蟲藉由躲避於糞鏈上而防止螞蟻捕食。幼蟲保持靜止不動，而且螞蟻也不能爬上蟲巢。然而懸巢舉尾蟻 (Crematogaster rogenhoferi) 可在蟲巢上爬行。當螞蟻快碰到糞鏈上的異紋帶蛺蝶 (Athyma selenophora) 幼蟲，幼蟲會藉由振動迫使螞蟻撤離。而這種振動行為目前尚未被報導。本研究探討異紋帶蛺蝶的「蟲巢」、「糞鏈」以及「振動」對於懸巢舉尾蟻的防禦效果。結果證實「振動」是高效率的防禦策略。在防禦入侵蟲巢的天敵方面，「振動」可能比「糞鏈」與「蟲巢」扮演著更重要的角色。而多了「糞鏈」的蟲巢比起單純的葉主脈蟲巢，有更高的幼蟲存活率。本研究對於節肢動物的防禦行為，提供了新的資訊。This study first discovered lepidopteran larvae could vibrate on frass chains hence increasing survival rate by vibration. How to survive during predation events is very important for prey. Under selection pressure, prey had developed a variety of defensing strategies. Constructing frass chain is one of the caterpillars’ behavioral defenses. Frass chain and mid-vein of a leaf formed a “refuge” for caterpillars. In previous studies, it had been demonstrated that caterpillars on frass chains could reduce predation rate of ants and keep motionless upon the approach of ants. The ants couldn’t climb on refuges. By contrast, Crematogaster rogenhoferi could climb on frass chains where the larvae of Athyma selenophora rested. When the ants were about to touch the larva on the frass chain, the larva would vibrate immediately. This might make the ants fall down from the frass chain. This vibration behavior had not been previously reported. Our study would examine how “refuge”, “frass chain”, and “vibration” would lower the predation rate respectively. We proved that “vibration” was an efficient defensing strategy. Compared to “frass chain” and “refuge”, “vibration” might play an important role on defensing. Refuge with frass chain had higher survival rate than mid-vein of a leaf. This study provided new information about defensive behavior of arthropod.