Conspicuous Color of Many Ladybug Species Indicates High Toxicity, Scares Off Avian Predators

For one of Britain's best-loved and most colorful group of insects, ladybirds (known as ladybugs in North America), the brightness of their color reveals the extent of their toxicity to predators, according to new research undertaken at the Universities of Exeter and Cambridge in the UK. The study, which was published online on June 5, 2015 in an open-access article in the journal Scientific Reports, also found that the more conspicuous and colorful the ladybird species, the less likely it is to be attacked by birds. The article is titled “Signal Honesty and Predation Risk Among a Closely Related Group of Aposematic Species.” Lina María Arenas, a Ph.D. student at the Centre for Ecology and Conservation at the University of Exeter and from the University of Cambridge, said: "Ladybird beetles are one of the most cherished and charismatic insects, being both beautifully colored and a friend to every gardener. Our study shows that not only does ladybird color reveal how toxic they are to predators, but also that birds understand the signals that the ladybirds are giving. Birds are less likely to attack more conspicuous ladybirds." Although red ladybirds with black spots are most familiar, ladybirds are a diverse group of species and come in many different colors and patterns, from yellow and orange to even camouflaged browns. The bright coloration of different ladybird species acts as a warning signal, telling potential predators to beware of the foul smelling, poisonous chemicals these beetles use for defense. The researchers measured toxicity using a biological assay, by counting the number of dead Daphnia (tiny crustaceans) in water containing the different ladybird toxins. The results show that five common ladybird species each have different levels of toxic defense.
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