Found only in rainforests in the Hawaiian islands, the spiders have a vast range of patterns and colours on their abdomens – yet all come from the same species.
The amazing diversity is due to genetic variations, although the patterns may also change depending on diet.

However, the species, which was discovered in 1973, is now under threat from the introduction of non-native animals to the islands.
The most common form – or ‘morph’ – is plain yellow and has no smile. But other variations are plentiful – the ‘red front’ morph pictured here with a cluster of her eggs is the second-most common.

The happy-face spiders feature in the new BBC2 documentary series South Pacific, which starts at 8.30pm tonight.