Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2010
Publication Date: 11/1/2010
Citation: Jiang, X.F., Luo, L.Z., Sappington, T.W. 2010. Relationship of Flight and Reproduction in Beet Armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), a Migrant Lacking the Oogenesis-flight Syndrome. Journal of Insect Physiology. 56(11):1631-1637. Interpretive Summary: The beet armyworm is a major pest of cotton and vegetables in much of the world, including the U.S. It overwinters in southern latitudes and migrates long distances northward each year to infest summer crops in the north. Many migratory insects display a pattern of development, called the oogenesis-flight syndrome, where migration takes place soon after reaching adulthood and before egg laying begins. We used laboratory flight mills to investigate the interaction between beet armyworm flight behavior and reproductive development in this species, and found that long-distance flight occurs at the same time as reproductive development. This independent relationship between flight and reproduction of adults suggests that developmental resources are partitioned between these activities during pupal development. Together, our results uncovered neither obvious trade-offs nor mutual suppression between flight and reproduction, which indicates the lack of an oogenesis-flight syndrome for coordination of these two energy-intensive processes. We propose a migration model for this species based on the current and previous studies. This conceptual model and the better understanding of the relationship between migration and reproduction in beet armyworm will improve population forecasting and early-warning systems in China and the U.S. It also will be useful to university, government, and industry scientists and modelers trying to understand and predict beet armyworm pest pressure on crops based on egg development in captured females.
Technical Abstract: The beet armyworm, Spodoptera exigua, undertakes long-distance migration. We used flight mills to investigate the interaction between flight and reproduction in this species given the apparent absence of the oogenesis-flight syndrome. This syndrome is characterized by a suite of traits common in many migratory insects including migration during the pre-oviposition period followed by a switch to oogenesis. No negative effects of inter-ovipositional flight on lifetime fecundity were observed. Instead, adult reproductive output suffered when female flight was initiated the first day after eclosion and before oviposition, suggesting that migratory flight overlaps with the oviposition period rather than being confined to the pre-oviposition period. Mating status of both females and males had no negative influence on their flight performance except that flight distance and flight duration of 7-d-old mated females were significantly less than in unmated females. Furthermore, the number of eggs produced and mating frequency of females less than 7 days of age were not significantly correlated with flight performance, suggesting reproductive development paralleled and was independent of migratory behavior. This independent relationship between flight and reproduction of adults is consistent with the very short pre-oviposition period in this species, and suggests that resources are partitioned between these activities during pupal development. Together, our results uncovered neither obvious trade-offs nor mutual suppression between flight and reproduction in S. exigua, which indicates the lack of an oogenesis-flight syndrome for coordination of these two energy-intensive processes. We propose a migration model for this species based on the current and previous studies.