Adult Motor Patterns Produced by Moth Pupae During Development

Abstract

Muscle potentials were recorded extracellularly from developing pupae and adults of the saturniid moths Antheraea polyphemus and A. pernyi and the sphingid moth Manduca sexta. During the week prior to the terminal ecdysis, developing moths still enclosed within the pupal cuticle produced motor patterns similar to those recorded from adults during flight and shivering. The pupal patterns had a longer cycle time and were more variable than the adult motor patterns. Characteristic inter-family differences in adult motor patterns were apparent in pupal motor patterns. Development of motor patterns was followed over several days by observing individuals with chronically implanted leads. Early in the pupal period potentials were small and infrequent. The amount of activity gradually increased and became more patterned. As development proceeded adult patterns were produced for increasing lengths of time, although the patterns changed quickly and spontaneously. Restricting the wing movements of A. polyphemus adults increased the cycle time, increased the number of spikes per burst in muscles opposing the restraint, and did not alter the interspike interval within a burst. The flight patterns produced by pharate moths, in which the wings are also immobile, also have a longer cycle time than that of adult flight, but the number of spikes per burst the same and the interspike interval is longer than in adult flight. These observations suggest that the differences between pupal and adult patterns are not necessarily due to the confinement of the wings by the pupal cuticle.