New research suggests the brightness of ladybugs' colors could give away their toxicity, and the more colorful they are the less likely they are to be eaten by birds.
Red ladybugs with black spots are the most common and well-known, but the insects actually come in variety of colors such as yellow and orange, the University of Exeter reported. This range of coloration is believed to act as a poison warning for hungry birds.
"[Ladybug] 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 [ladybug 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," said Lina María Arenas, a PhD student at the Centre for Ecology and Conservation at the University of Exeter and from the University of Cambridge.
A team of researchers measured toxicity by counting the number of dead Daphnia (tiny crustaceans) in water containing the defense poison from different ladybugs. They found toxicity varied among different ladybug species, and those with the brightest colors were the most toxic.
"Our results tell us that the ladybirds present 'honest' signals to predators, because their colour reveals how well defended they are," said Martin Stevens from the University of Exeter. "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 team also photographed ladybugs using cameras that are sensitive to ultraviolet light, allowing them to use special modeling and image analysis technique to determine how the beetles would appear to birds. They found the birds would be able to recognize differences in coloration, and were less likely to attack brighter bugs.
The findings were published in a recent edition of the journal Scientific Reports.