Sunday, December 24, 2006
An open access/free paper (includes video) from PLoS ONE:
Predator Mimicry: Metalmark Moths Mimic Their Jumping Spider Predators
Cases of mimicry provide many of the nature's most convincing examples of natural selection. Here we report evidence for a case of predator mimicry in which metalmark moths in the genus Brenthia mimic jumping spiders, one of their predators. In controlled trials, Brenthia had higher survival rates than other similarly sized moths in the presence of jumping spiders and jumping spiders responded to Brenthia with territorial displays, indicating that Brenthia were sometimes mistaken for jumping spiders, and not recognized as prey. Our experimental results and a review of wing patterns of other insects indicate that jumping spider mimicry is more widespread than heretofore appreciated, and that jumping spiders are probably an important selective pressure shaping the evolution of diurnal insects that perch on vegetation.
The phenomenon of mimicry, a high degree of resemblance due to selection, was first proposed in 1862 by Sir Walter Henry Bates (info) upon his return from eleven years as a professional collector in Amazon. Writing about butterfly wing patterns, Bates noted, "... on these expanded membranes Nature writes, as on a tablet, the story of the modifications of species..." Bates proposed that longwings and other butterflies gain protection by mimicking distasteful species and that the resemblances among such unrelated insects lent support to Charles Darwin's newly proposed theory of natural selection . Since Bates's initial contribution various cases of mimicry have been identified from across the tree of life. In this paper, we describe a curious form of Batesian mimicry - again involving the wing patterns of Lepidoptera - in which prey (metalmark moths) obtain protection by mimicking their predators (jumping spiders)
Many examples of Batesian and Mullerian mimicry and camouflage have been described –. Even cases of aggressive mimicry, where predators mimic prey, are known (e.g., females of Photuris fireflies lure males of different firefly species to their death by mimicking their courtship signals ). However, predator mimicry - cases in which prey have evolved to mimic their predators to thwart predation attempts - are both exceptional and rare.
Predator mimicry was suggested for owls, where owl ear tufts mimic mammalian predators for protection from such predators as lynx, fox, and marten . Another potential case of predator mimicry is among South American cichlids: coloration and spotting of certain prey species makes them so similar to their predators that they are thought to be their mimics . Eyespots on the wings of giant silk moths and other Lepidoptera undoubtedly mimic eyes of mammalian predators - but here the eyes may function not to mimic their would-be predators, but to resemble a much larger animal, one sizable enough to be a threat to lepidopteran would-be predators. Hence, these eyespots might be regarded as startle coloration . However, in none of these cases are there experimental data demonstrating the efficacy of this mimicry. Our literature review suggests there are few well-supported cases of predator mimicry: e.g., lycaenid butterflies that chemically mimic ants  and salticid spiders that mimic ants to avoid being preyed upon by them  (other ant mimics probably gain protection from all predators that tend to avoid ants ). Here we present evidence for another case of predator mimicry involving salticid spiders, but in this case salticids are predators and not prey.
Citation: Rota J, Wagner DL (2006) Predator Mimicry: Metalmark Moths Mimic Their Jumping Spider Predators. PLoS ONE 1(1): e45. doi:10.1371/journal.pone.0000045
"There are three forms of mimicry utilized by both predator and prey: Batesian mimicry, Muellerian mimicry, and self-mimicry. Mimicry refers to the similarities between animal species; camouflage refers to an animal species resembling an inanimate object..."
*David Wagner is author of "Caterpillars of Eastern North America : A Guide to Identification and Natural History"
From the Preface:
"I recently attended a seminar at Harvard University to hear Stefan Cover speak. He started off simply enough. "Everyone needs an obsession. Mine is ants." Everyone chuckled … more than a few heads nodded in agreement. For the past ten years mine has been caterpillars. They have provided a bounty of trip memories, abundant photographic opportunities, led to dozens of collaborations and friendships, some of which will be lifelong, and introduced me to a world full of beauty, change, carnage, and discovery. Stefan was right.
My goal in writing this guide is twofold. First, to provide larval images and biological summaries for the larger, commonly encountered caterpillars found east of the 100th meridian. Sounds simple, yet the problems associated with compiling such information are legion: literature is scattered, lacking, or, worse, especially in the case of some early accounts, wrong. For many common moths the species taxonomy is still under study, life histories are incompletely known, and distributional data have yet to be assembled. In this guide I offer a synopsis for each species that includes information on its distribution, phenology, and life history.
...Behaviors and phenomena previously believed to be exceptional or uncommon are shown to be otherwise: e.g., both Batesian and Mullerian mimicry appear to be more prevalent in caterpillars than previously recognized. Pronounced developmental changes (in form, coloration, and behavior), bordering on hypermetamorphosis, were seen in several families - striking examples occur among the daggers and slug caterpillars..."
Technorati: predators, mimicry, video, spiders, natural selection, insects, evolution, theory, charles darwin, tree, life, batesian, mullerian, butterflies, ants, self, caterpillars, discovery, taxonomy