Seasonal wing dimorphism and life cycle of the mole cricket Gryllotalpa orientalis (Orthoptera: Gryllotalpidae)

Chihiro Endo

doi:10.14411/eje.2006.098

Abstract

Control of seasonal wing dimorphism in the oriental mole cricket Gryllotalpa orientalis Brumeister (1839) from a wetland habitat in western Japan is described. The long-winged (LW) morph appeared from mid-June to September, whereas the short- winged (SW) morph appeared from September to mid-June. Individuals overwintered in either the adult or juvenile stage. The sea- sonal shift in wing morphology was linked to the overwintering stage. Individuals that hatched in May became SW adults in September-October and then overwintered, whereas those that hatched in June and July overwintered as juveniles and became LW adults in June of the following year. The life cycle of both morphs was univoltine. Reproductive benefits and constraints of each wing morph of G. orientalis are compared.

Highlights

In many pterygote insects, wing polymorphism, i.e., the presence of macropterous individuals and obligate flightless individuals, has been classified as a type of dispersal polymorphism (Harrison, 1980; Roff, 1986; Zera & Denno, 1997)
Seasonal wing polymorphism has been found in organisms with multivoltine life cycles, and the favoured morph differs between the first and second or later generations (e.g., Harada, 1996; Van Dyck & Wiklund, 2002; Olvido et al, 2003)
In G. orientalis, differences in wing morphology are linked to the overwintering form

Summary

Introduction

In many pterygote insects, wing polymorphism, i.e., the presence of macropterous (long-winged) individuals and obligate flightless (wingless or with reduced wings) individuals, has been classified as a type of dispersal polymorphism (Harrison, 1980; Roff, 1986; Zera & Denno, 1997). When the population density is low and competition for food and mates is not severe, individuals do not need to disperse and short-winged (SW) or wingless morphs would be favoured. When the population density is high and the competition is severe, the long-winged (LW) morph, which can disperse to a better habitat, would be favoured. Seasonal wing polymorphism has been found in organisms with multivoltine life cycles, and the favoured morph differs between the first and second or later generations (e.g., Harada, 1996; Van Dyck & Wiklund, 2002; Olvido et al, 2003). The selection pressure varies seasonally, and the favoured morph is fixed for each season. It is important to determine how wing polymorphism is maintained in the life cycles to understand why it is maintained

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Conclusion