Relationship of flight and reproduction in beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), a migrant lacking the oogenesis-flight syndrome

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, common in many migratory insects, is characterized by a suite of traits 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-day-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 conceptual model of migration for this species based on the current and previous studies.

Cloning of the heat shock protein 90 and 70 genes from the beet armyworm, Spodoptera exigua, and expression characteristics in relation to thermal stress and development

“…Life history strategies of S. exigua, such as overwintering (Jiang et al 2001), migration, and reproduction under various temperature, humidity, density, and food conditions, have been well documented in our previous studies, showing substantial environmental tolerance and ecological plasticity in this species (Jiang and Luo 1998b;Jiang et al , 2000Jiang et al , 2002Jiang et al , 2010Wang et al 2008). Furthermore, S. exigua is also known for its rapid development of resistance to many chemical pesticides and its lack of susceptibility to transgenic Bt crops (Wang et al 2002;Lin et al 2007;Wu et al 2008;Jia et al 2009;Lan and Zhao 2010).…”

Wing reduction influences male mating success but not female fitness in cockroaches

“…Indeed, such trade-off between investment into flying apparatus and reproduction (flight-oogenesis hypothesis) was repeatedly demonstrated in plentiful intrasexual wing dimorphic Orthoptera 13–15 , Hemiptera 16, 17 , or Lepidoptera 18, 19 . However, several studies do not provide support for this trade-off between energy costs of wing maintenance and reproduction 20–23 , suggesting that it is not the sole reason behind wing loss. Nevertheless, virtually all studies have focused on fitness of females, while little attention was paid to the fitness of males 24, 25 .…”

Synchronized Oviposition Triggered by Migratory Flight Intensifies Larval Outbreaks of Beet Webworm

“…Lifetime fecundity may be decreased, as in the fruit fly, Drosophila melanogaster [6], and noctuid moths, Heliothis virescens , Pseudoplusia includens and Spodoptera exempta [17]–[19], or increased, as in the milkweed bug, Oncopeltus fasciatus , and migratory grasshopper, Melanoplus sanguinipes [20], [21]. Lifetime fecundity of the black bean aphid, Aphis fabae [22], and beet armyworm, Spodoptera exigua [23] is unchanged by flight, while that of the chloropid fly, Oscinella frit , and oriental armyworm, Mythimna separata varies with flight age [24], [25]. In some species, flight promotes ovarian development or shortens the length of POP [13], [18], [24]–[26].…”