Insect neurometamorphosis. IV. Effects of the brain and synthetic α‐ecdysone upon interganglionic connective shortening in Galleria mellonella (L.) (Lepidoptera)

The interganglionic connectives of pharate pupae and pupae < 5 hours after ecdysis (early pupae) of Galleria mellonella will cease shortening if the segments in which they lie are separated from the prothorax. Though shortening is not prevented by removing the brain of an early pupa, it will be delayed several days. This period is prolonged to more than a week if the corpora cardiaca (Cc) and corpora allata (Ca) are removed together with the brain. The retardation induced by extirpating all three organs is prevented by implanting a single brain from a pupa or an adult, but not by implanting ganglia. It is also alleviated, to a lesser extent, by one or two pairs of Cc‐Ca. As many as three brains transplanted into a posterior pupal fragment deviod of acknowledged endocrines will not initiate shortening, but implanting a single brain into a decerebrated anterior fragment will. The evidence suggests that the brain does not regulate shortening directly. Instead, it may do so by producing prothoracotropic hormone. Approximately 0.03 μg of synthetic α‐ecdysone per animal is sufficient to cause 50% of the meso‐metathoracic connectives of brainless pupae to shorten half their initial length or more within three days. For posterior pupal fragments, however, ca. 0.06 μg per animal is required. The sensitivity of this developing system to ecdysone parallels its responsiveness to transplanted brains, and the shortening nerve cord may be useful in assaying for brain hormone.