Original air date: 1 January 2015
The table below shows a timeline of what happens in the episode
The composition of butterfly wings. Some are like tiles on a roof (top left), others contain pigments (top right), yet others contain pigments that reflect certain colours.
Flies have only a single pair of wings, the other pair was reduced to halteres. These are sensors that, combined with the insect eyes, work like human-made gyroscopes.
The halteres (top) and how they work (bottom left) and at full stretch (right)