Ladybug's Bright Colors Warn Predators of How Toxic They Are

First Posted: Jun 05, 2015 07:58 AM EDT

Most people enjoy colorful ladybugs. However, what most people don't know is that these insects are brightly colored to reveal their toxicity to predators. Now scientists have taken a closer look at how likely ladybugs are to be attacked by birds.

"Ladybird beetles are one of the most cherished and charismatic insects, being both beautifully colored and a friend to every gardener," said Lina Maria Arenas, one of the researchers, in a news release. "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."

While red ladybugs with black spots are the most familiar, ladybugs are a diverse group and come in many different colors and patterns. These range from yellow and orange to camouflaged browns. The bright coloration of different ladybug species acts as a warning signal to tell potential predators to beware of the foul, poisonous chemicals they use as a defense.

The researchers measured the toxicity of the ladybugs by counting the number of dead Daphnia, which are tiny crustaceans, in water containing different ladybug toxins. This revealed that five common ladybug species each have different levels of toxic defense. The species that were the most colorful against natural vegetation were also the most toxic.

"Our results tell us that the ladybirds present 'honest' signals to predators, because their color revelas how well defended they are," said Martin Stevens, one of the researchers. "Relatively inconspicuous species, such as the larch ladybird, have low levels of defense and place more emphasis on avoiding being seen, whereas more conspicuous and colorful species, such as the 2-spot ladybird, openly flaunt their strong defenses to predators like birds."

The findings reveal a bit more about these insects and show that color is linked to toxicity. This, in turn, shows a bit more about the process of evolution in these insects.

The findings are published in the journal Scientific Reports.

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