Coloured scanning electron micrograph (SEM) of puparia of the fruit fly (Drosophila melanogaster). At left is an intact puparium before the eclosion of the adult. The fibres on its surface are from the paper background. The lower puparium has split, and the emerging fly is visible. A puparium is the hardened outer skin of the final larval instar, inside which the larva undergoes metamorphosis. Most of its cells die, but some (in regions called imaginal discs) develop the adult structures such as compound eyes (red), legs, antennae or wings. The fly escapes by inflating its head (visible here). Still with a soft exoskeleton, it thrusts its head forwards and performs pulsed contractions of its body to free itself. D. melanogaster is a model organism for research due to its short life cycle and simple genetic makeup. This fly is the variety Oregon R. The colours are false. Magnification: x60 at 10x8.