LIFE CYCLE OF LABORATORY-REARED TOBACCO HORNWORMS,MANDUCA SEXTA, A STUDY OF DEVELOPMENT AND BEHAVIOR, USING TIME-LAPSE CINEMATOGRAPHY

Abstract

1. Time-lapse cinematography was used with laboratory-reared specimens of M. sexta to obtain information on and timing of behavioral activities.2. Insects used in this study were selected as the most advanced group within any instar and thus were the first of the gate-I insects. Use of these insects avoided timing irregularties involving the gating phenomenon. These advance insects varied less than ±0.9% s.d. from hatch through pupation.3. A detailed description was given for each of more than 20 timed events. Emphasis was placed on the events that occurred between the fifth ecdysis and pupation.4. Hatch occurred four days after oviposition (time 0), and ecdyses of the remaining four larval instars were at 6.4, 8.4, 10.6, and 13.7 days; pupation occurred at 22.8 days. The larvae underwent molt sleep in which they did not feed, defecate, or move until ecdysis. Durations of molt sleep were from 14 to 25 hr for each of the larval-larval ecdyses. The fifth instar did not have a comparable stage.5. Growth rate was highest for the first-instar larvae and slowest for the fifth instar, with weight-doubling times of 11.3, 17.6, 11.4, 17.3, and 21.2 hr for the first through fifth instar feeding periods, respectively, at 25° C.6. Body wetting, found only in the last instar, was induced by the onset of the scotophase. Use of this event marker allowed the selection of a group of insects that were capable of pupating five days later within one hour of each other.