The effect of larval phase on flight performance of African armyworm moths, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae)

Abstract

The characteristics of the high and low density forms of noctuid moths, including Spodoptera exempta (Walker), exhibiting a density-dependent phase polyphenism have frequently been discussed in relation to migration. However, the only previous (unpublished) demonstration of an effect of larval phase on adult flight performance, using a tethered-flight technique, was invalidated by the recent discovery that the principal determinant of flight potential in S. exempta is genetic. When the incidence of prolonged flight was measured in moths derived from genetically-matched (full-sib) samples, there was a clear increase in long flights by females derived from the high-density gregaria phase larvae compared with those from solitaria phase larvae. The reasons for the apparent absence of a similar effect in males is not clear, but it is possible that the tethered-flight technique provides a less reliable index of flight capacity in this sex. The characteristics and significance of phase polyphenism in migratory noctuids are discussed. It is suggested that, in S. exempta and possibly some other comparable species, the high-density phase is adapted to accelerate re-dispersal after populations become concentrated, in order to escape the detrimental consequences of high larval densities.

Predictive Adaptive Responses: Condition‐Dependent Impact of Adult Nutrition and Flight in the Tropical ButterflyBicyclus anynana

“…A similar 5-min flight treatment was recently used in the speckled wood butterfly and was shown to have strong negative fitness effects, partly dependent on the landscape of origin (Gibbs and Van Dyck 2010). Other studies have also found changes in dispersalrelated morphological traits in Lepidoptera (e.g., an allometric relationship between body mass and wing length, wing loading, wing shape) in response to food quality, food quantity, or rearing density during development (Woodrow et al 1987;Boggs and Freeman 2005;Pellegroms et al 2009). In general, studies demonstrating that flight capability in wing-monomorphic species may also be a phenotypically plastic trait remain few in number, especially in comparison to the studies on wing-dimorphic species (reviewed in Zera and Denno 1997).…”

“…Therefore proxies, such as relative thorax mass (e.g., Berwaerts and Van Dyck 2004), flight endurance (e.g., Parker and Gatehouse 1985b), or flight metabolic rate (e.g., Niitepõld et al 2009), that often correlate with dispersal or flight ability have been used. Nevertheless, few studies on wing-monomorphic species have also demonstrated some adaptive plasticity in flight capacity or related morphological traits (Parker and Gatehouse 1985a;Woodrow et al 1987;Senger et al 2008;Pellegroms et al 2009). …”

Effects of phenotypic plasticity on pathogen transmission in the field in a Lepidoptera-NPV system

“…This is known as density-dependent phase polyphenism. The high-density form is also associated with shorter larval duration and increased migratory ability in the adults (Simmonds and Blaney 1986;Gunn and Gatehouse 1987;Woodrow et al 1987). The susceptibility of S. exempta to its NPV varies with rearing density, with the melanised, high-density form having an LD 50 ten times higher than that of the typical solitary form ).…”

Transgenerational effects modulate density-dependent prophylactic resistance to viral infection in a lepidopteran pest

“…This may well be true for some phase-polyphenic insects, like Spodoptera caterpillars, that use density-dependent cues to trigger phenotypic changes that enhance dispersal to lower densities [22] and where trade-offs with constitutive immunity have been identified [13,16,23,24]. Alternatively, crowding-induced upregulation of immune function (or other costly phenotypic changes associated with phase-change) may deplete parents of resources that would otherwise be invested in offspring.…”