Modified Ultrsonic Actograph for Monitoring Activity of Lepidopterous Larvae

Abstract

An ultrasonic actograph was modified to detect the slow movements typical of lepidopterous larvae. A differential instrumentation amplifier increased the sensitivity of the instrument. Activity patterns of 5th instars of Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae) and Sabulodes aegrotata Guenee (Lepidoptera: Geometridae) were determined using the modified actograph. S. exigua larvae were active ca. 339 minutes of the day with significantly greater photophase activity during 0600-1000 and 1100-1300 hrs as compared to scotophase activity during 0000-0400 and 2200-2400 his. S. aegrotata larvae were active ca. 421 minutes of the day with greater activity during the scotophase period.