[The course of melanization and its inhibition in pupae of the cabbage whitePieris brassicae L.]

The melanization of the Cabbage White pupae varies in response to light conditions. As abdomina, which are isolated by a ligature, become strongly melanized, the control evidently works in the way of gradual inhibition.The melanine patches of light pupae are not paler than those of dark pupae, but they are smaller. Apparently there is a gradient of reactivity to inhibition from the margin of the patches towards their center. Different patches are affected by the inhibition to a different extent.The black patches appear during the first 6 hours after pupation, not simultaneously but in a certain sequence. The first and the last patches of this sequence are most reactive to inhibition. On light pupae they may be entirely absent.A classification of pupal melanization is based on differences in the shape of certain patches, which can easily be recognized even on operated pupae and isolated parts of the body.Equally strong melanization as from ligating results from nerve section between brain an suboesophageal ganglion, somewhat weaker melanization results from section between suboesophageal and prothoracic ganglia.The melanizing effects of ligatures and nerve sections decrease during a critical period. They are entirely lost 12 hours after the prepupa has fastened itself to the ground by spinning the girdle-thread.It is suggested that during this critical period a melanization inhibiting factor is secreted by a thoracic center, which itself is under nervous control of the brain.