As children, we have all been taught an old English nursery rhyme about ladybugs, dating back to 1744 that has several versions. One goes, “Ladybird, ladybird, fly away home, Your house is on fire, and your children shall burn!”
There is a lot more to the ladybug than just the good luck one would have in gently blowing a breath of air their way to get them to fly away home. The little beetle’s gloriously bright colors play an important role in keeping them safe from predators.
Researchers at the Universities of Exeter and Cambridge wondered about how insects protect themselves from predators. There is one kind of protection that involves camouflage, an insect looking like a leaf or twig being a good example. The other kind is the bright, almost vivid coloration of some amphibians telling predators they are toxic to the touch.
The researchers surmised that acting like a stick made a lot of sense, much more so than boldly standing out in a crowd like the bright red ladybug with big black spots. It is almost an advertisement saying, “Here I am. Come get me.” The researchers found out the brighter the coloration of the ladybug, the more toxic it was.
Lina María Arenas is a PhD student at the Centre for Ecology and Conservation at the University of Exeter and from the University of Cambridge. Science news online quotes her as saying, “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.”
Researchers measured the toxicity of ladybugs by counting the dead daphnia in water containing the defense poisons from different ladybugs. They found different toxicity levels depending on the coloration of the particular ladybug defense poison being tested. They also used cameras sensitive to ultraviolet light to determine how the beetles appeared to birds. The team found that birds were able to differentiate between the more colorful ladybugs and were less likely to attack.
The researchers were able to show that the level of intensity of coloration was directly indicative of the levels of toxicity and therefore defense. The team further proved the intensity of the colors were honest signals, and in no way misleading. The report was altogether most interesting and gives us insight into a most unusual means of defense used by world’s favorite little beetle.
This study was reported in the journal Scientific Reports on June 5, 2015 under the title: “Signal honesty and predation risk among a closely related group of aposematic species”