Why are ladybirds so pattern variable?

BBC Wildlife contributor Helen Roy answers your wild question.

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22-spot ladybird

22-spot ladybird © Keith Porter / Getty

 

Ladybirds are indeed varied, ranging in appearance from dull brown to bright yellow and black.

From an evolutionary perspective, all aposematic ladybirds (those whose markings warn predators of a foul taste) should look the same, thereby giving a consistent message. Yet great variation exists, not only between species but between individuals of the same species.

Take the two-spot. Typically red with two black spots, it can also be black with four or six red spots. Studies have shown that it is more palatable than other species and thus mimics its more toxic relatives as a form of defence.

Studies also suggest that colour pattern varies with temperature, and that dark forms gain advantages in cooler conditions because they heat up faster than their lighter counterparts, a process known as thermal melanism.

Indeed, there is tantalising evidence that the dark colour forms of many insects inhabit cooler places, and research has revealed that the black spots on harlequins are larger when individuals have pupated at lower temperatures.

Females also show a preference for mating with particular colour forms – two-spots prefer melanic males.  

 

Read Helen's article on the secret life of 7-spot ladybirds in our August 2017 issue.

 

 

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