The Ladybirds' Poisonous Colors Warn Off Potential Predators

A ladybird is one of Britain's best-loved and colorful groups of insects. Yet did you know its brightness shows a bit more than how strikingly beautiful these little bugs are? It is actually a warning to predators about how toxic it is. The findings are published in the journal Scientific Reports.

Lina María Arenas, a PhD student at the Centre for Ecology and Conservation at the University of Exeter and from the University of Cambridge said, in a news release: "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."

Though red ladybirds with black spots are the 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. In fact, some with extremely bright colorations are actually warning predators to beware of their foul smelling, poisonous chemicals that help to push predators away.

For the study, researchers measured their toxicity by counting the number of dead Daphnia-tiny crustaceans-in water containing different ladybird toxins. Results revealed five common ladybird species, each having different levels of toxic defence. Those who were the most colorful and conspicuous were also the most toxic.

"Our results tell us that the ladybirds present 'honest' signals to predators, because their color reveals how well defended they are," added Dr Martin Stevens from the University of Exeter.

"Relatively inconspicuous species, such as the larch ladybird, have low levels of defence and place more emphasis on avoiding being seen, whereas, more conspicuous and colorful species, such as the 2-spot ladybird, openly flaunt their strong defences to predators like birds."

Later, the researchers also used ultraviolet light in special cameras to see how the bugs would appear to birds, revealing a very different color vision from what humans see. Findings showed that the birds quickly saw what was more poisonous based on the bright and vibrant colors of the poisonous beetles.

The findings, one of the first to cover the topic, demonstrate how toxic creatures may live longer because they are less likely to be taken over by predators due to their warning smells and colors.

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