Why are ladybugs so colorful?

Rather than trying to blend in, ladybugs make a counterintuitive effort to stand out. Here’s why.

There are two kinds of bugs in this world, the shy “pretending like I’m a stick here” types and the loud and brassy, “the brighter the better” kind. Insects that camouflage? That makes sense. It’s hard to be eaten by a predator if you can’t be seen. But what advantage do their brightly colored brethren have?

That’s what researchers at the Universities of Exeter and Cambridge set out to find in a recent study about everybody’s favorite beetle, known by many as the ladybird. The study, published in the journal Scientific Reports, found that the more conspicuous and colorful the ladybug species, the less likely it is to be attacked by birds.

As it turns out, the ladybug’s color serves as a courteous warning to would-be eaters – the brighter the bug, the more toxic its poison. And the birds who eat them, know.

Alexey Kljatov/Flickr/CC BY 2.0Lina María Arenas, from the University of Cambridge says, "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 the classic standard ladybug – red with black spots – are the ones we know best, they come in a rainbow of colors. Well not exactly a rainbow, but from the bright red we know to deeper rusts and a range of tones from yellow to orange and browns.

The researchers measured toxicity using a biological assay and found that five common ladybug species each have different levels of toxic defense. Those species with the most vibrant colors in comparison to their habitat’s vegetation were shown to be the most toxic.

siamesepuppy/Flickr/CC BY 2.0Dr Martin Stevens from the University of Exeter says, "Our results tell us that the ladybirds present 'honest' signals to predators, because their color reveals how well defended they are. 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 study is the first to show comprehensively that standing out provides a warning signal to how toxic the species are. And in turn more toxic – and conspicuous – species are less likely to be attacked in the wild ... yet more likely to be admired by ladybug lovers.

Tags: Insects | Nature Blows My Mind


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