QotW - Why do ladybirds differ in their spots?

This week, Eva Higginbotham's been going dotty trying to answer this question from listener Ruomei...

Ruomei - Why do ladybugs have a different number of spots on their backs?

Eva - Now, I have always wanted to know the answer to this back in the playground everyone said it was about which branch of a tree the ladybird was born on, which I must admit, I totally believed for a really long time. But to get the real answer to this question, I enlisted the help of ladybird enthusiastic Helen Roy from the UK Centre for Ecology and Hydrology.

Helen - Some insects are spotty, some striped and some simply quite blotchy or not patterned at all. And it actually can take a day or two for the colours of an adult ladybird to appear after it first emerges from the cozy confines of its pupa. It's really fascinating to watch this happen. And I can remember as a six year old, seeing some bright yellow and translucent ladybirds on the vegetable patch and within hours, the red colour and seven black spots began to appear. These were seven spot ladybirds, and they would have exactly seven spots throughout their adult life. Ladybirds do not get more spots as they age, but interestingly, the spot number in some species can vary a lot, so the two spot ladybird can have two or four or six spots.

Eva - Largely it comes down to what species of ladybird you're actually looking at and kind of like our eye colour, whatever you have once the pigment has come in is what you are set with for life. But why do they have these colourful patterns in the first place?

Helen - The bright colours and contrasting patterns of some ladybirds are called warning colours. The lady bird is giving a clear message to other species that might be tempted to eat them, that they taste horrible. Perhaps you might be thinking, but why don't all ladybirds look the same and so give the same warning message that predators could learn just one message. It's most likely that this is the contrasting colours that are important, and whether it's black on yellow or red on black or two spots or 24 spots, it really doesn't matter. But also different colour patterns can provide benefits beyond warning predators, ladybirds with bigger or more spots can warm up more rapidly than those with smaller or fewer spots. And sometimes it can be beneficial for the lady bird to hide. And so the colour pattern might provide camouflage in some situations, ladybirds are just amazing!

Eva - I'll agree with that. Thanks Helen. Next week, we're racking our brains for the answer to this question from David.

David - How much of your brain is actual memory?