Submitted to: Environmental Entomology
Publication Type: Review article
Publication Acceptance Date: 4/15/2011
Publication Date: 6/1/2011
Citation: Jiang, X., Luo, L., Zhang, L., Sappington, T.W., Hu, Y. 2011. Regulation of migration in Mythimna separata (Walker) in China: A review integrating environmental, physiological, hormonal, genetic, and molecular factors. Environmental Entomology. 40(3):516-533. Interpretive Summary:
Technical Abstract: Each year the oriental armyworm, Mythimna separata, undertakes a seasonal, long-distance, multigeneration roundtrip migration between Southern and Northern China. The developmental decision to migrate is facultative and controlled by environmental, physiological, hormonal, genetic, and molecular factors. Larvae that experience temperatures above or below certain thresholds accompanied by appropriate humidity, short photoperiod, poor nutrition, and moderate density tend to develop into migrants. However, there is a short window of sensitivity within 24 h after adult eclosion during which an erstwhile migrant can be induced to switch to a reproductive resident. The switch is triggered if the newly enclosed adult encounters extreme environmental factors including starvation, low temperature, or long photoperiod. This window thus provides an opportunity for secondary regulation of migration in the adult stage. Adult migrants begin flight the first or second night after eclosion, and migration proceeds during an approximate 7-day pre-oviposition period, a pattern of temporal partitioning of migratory flight and reproductive activities termed the "oogenesis-flight syndrome." Decisions to develop into migrants or residents in both the larval and adult sensitive stages are controlled by juvenile hormone (JH) titers. The insect neuropeptide allatotropin regulates adult flight and reproduction through its role in activating the corpora allata to synthesize JH. Additive genetic effects influence migratory behavior, but individuals retain flexibility in expression of both migration and reproductive life history traits. A conceptual model of M. separata migration is presented, and future research directions to better understand regulation of migration in this species are discussed.