Oviposition periodicity, egg morphology and life history of large cabbage moth Crocidolomia pavonana population in Samoa

Abstract

A study on the biology and behaviour of the Samoan population of Crocidolomia pavonana was carried out through a series of experiments. The study showed that C. pavonana completes its life cycle in 24-35 days. Female emerge, mate and oviposit (as egg mass) during the scotophase. The average size of egg mass was 9.0 ± 0.48 mm² and the mean number of eggs oviposited were significantly (P<0.05) greater in scotophase than photophase. The age of the female was correlated negatively to daily oviposition and a decrease in oviposition was recorded after 15 days, which was also less than 1 egg mass per day. The colour of newly oviposited egg mass was light-green changing yellow after two days and black on the subsequent day. The larvae passed through four instars before it was found to undergo pupation. The duration of the first instar was smaller than the fourth instar. Males took a slightly longer time to develop from pupae (10.19 ± 0.22 vs 9.52 ± 0.17 days), and lived longer than females (27.0 ± 1.01 vs 19.8 ± 1.14 days). The Samoan C. pavonana oviposits small egg masses. This information could be used to develop effective pest management using the recently identified egg parasitoid Trichogramma chilonis.