Novel Fraction Collector for Studying the Oviposition Rhythm in the Turnip Moth

Abstract

Turnip moths, Agrotis segetum (Schiff.) (Lepidoptera: Noctuidae), were held in a transparent plastic box with a window opening to a rotating paper drum upon which the females could lay eggs. A novel fraction collector, consisting of a standard 24-hr wall timer and simple electronic circuit, served to rotate the paper in hourly increments. The entire apparatus was housed in an environmental chamber on a 16 hr light: 8 hr dark photoperiod at constant 23.7°C and 55% r.h. Under these conditions a circadian rhythm of egg laying was indicated with a mean activity time 0.2 hr before dark and standard deviation of 2.1 hr. The relative egg productions during the second to seventh day of oviposition peaked on the third day. Differences in the circadian rhythms of mating and oviposition are considered in terms of ecological fitness.

Key Words:

• Agrotis segetum
• turnip moth
• Noctuidae
• circadian rhythm
• oviposition
• fraction collector
• timer