Feeding of Tobacco Hornworm Larvae Under Different Light Conditions as Indicated by Fecal Evacuations

Abstract

The periodicity of fecal evacuations of tobacco hornworm larvae (Mandue a sexto) was monitored throughout the total larval phase in constant light, constant darkness, and a fall rhythm of light and darkness. By observation of feeding behavior and fecal evacuations of larvae, the time relationship of fecal evacuation and ingestion was recorded. The interval between initial ingestion and first evacuation averaged 3.75 hr. During the intervals between molts the larvae actively fed in periods averaging 14 min. The average length of feeding periods between molts was 58 hrs and the length of molting periods 22 hrs. The total larval phase covered 375 hrs in the fall light-dark cycle, 358 hrs in continuous darkness, and 407 hrs in continuous light. The total larval phase and the total numbers of fecal pellets evacuated in the different light regimes were not significantly different.