有毒的虎蛾历史上是有警告色的昆虫的著名例子；后来人们发现，蝙蝠将这些昆虫所产生的超声波与毒性联系在一起，而且无毒物种也能得益于发出类似的声音。

    在对加拿大东南安大略26种蛾子所做的一项研究中，John Ratcliffe 和Marie Nydam发现，虎蛾的警告信号随着一年中时间的不同而变化，因此也随着它们最有可能碰到的捕食者的类型而变化。在春天出现的蛾子物种，往往用视觉信号如鲜艳的色彩来警告捕食者，告诉它们自己是不能吃的，因为在春天鸟类是其最大的威胁。在夏天出现的蛾子物种更多地依靠超声来赶走能够进行回声定位的蝙蝠，后者在夏季对其构成主要威胁。同样，在白天活跃的物种更多地依靠视觉警告信号，而超声信号在晚上更有用。

    这项研究说明了，来自两种截然不同捕食者的选择压力何以能够引导昆虫警告系统中不同组成部分的演化，从而导致同一物种内拥有多样化的对抗捕食者的防卫体系。

推荐原始出处：

Nature 455, 96-99 (4 September 2008) | doi:10.1038/nature07087

Multimodal warning signals for a multiple predator world

John M. Ratcliffe^1,3 & Marie L. Nydam^2,3

^{1 Center for Sound Communication, Institute of Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
2 Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York 14853, USA
3 These authors contributed equally to this work.}

Aposematism is an anti-predator defence, dependent on a predator's ability to associate unprofitable prey with a prey-borne signal¹. Multimodal signals should vary in efficacy according to the sensory systems of different predators; however, until now, the impact of multiple predator classes on the evolution of these signals had not been investigated^2, 3. Here, using a community-level molecular phylogeny to generate phylogenetically independent contrasts, we show that warning signals of tiger moths vary according to the seasonal and daily activity patterns of birds and bats—predators with divergent sensory capacities. Many tiger moths advertise chemical defence^4, 5 using conspicuous colouration and/or ultrasonic clicks^3, 6. During spring, when birds are active and bats less so, we found that tiger moths did not produce ultrasonic clicks. Throughout both spring and summer, tiger moths most active during the day were visually conspicuous. Those species emerging later in the season produced ultrasonic clicks; those that were most nocturnal were visually cryptic. Our results indicate that selective pressures from multiple predator classes have distinct roles in the evolution of multimodal warning displays now effective against a single predator class. We also suggest that the evolution of acoustic warning signals may lack the theoretical difficulties associated with the origination of conspicuous colouration.