• 1
    The digging movements of the freshly emerged flies have been described and analysed. Direction of digging is determined by light, but not by gravity.
  • 2
    The process of the inflation of the fly with air and the expansion of the wings has been described and analysed. During digging these reactions are inhibited and postponed. Air-pumping occurs apparently independently from external and internal stimuli; it starts automatically a certain time after emergence and stops automatically after a certain period.
  • 3
    It has been experimentally proved that the first filling of the air-sacs is due to negative pressure in the body arising from the diffusion of air out of the gut (in accordance with a hypothesis of Evans).
  • 4
    Colouring and hardening of the skin are inhibited and postponed during prolonged digging.