Wing dimorphism in the migratory locust,Locusta migratoria: differentiation of wing morph and phase polyphenism

Abstract

AbstractA short‐winged morph was recently discovered in the migratory locust,Locusta migratoria. It is different from the normal, long‐winged morph not only in forewing length but also in hind femur length, displaying a dimorphism. To understand the significance of this dimorphism, other morphological characters were compared between the two morphs, and the time of differentiation of wing‐pad length was investigated. Wing weights were heavier in the long‐winged morph than in the short‐winged morph. This result showed that the short‐winged morph is not formed by a failure of wing expansion. No obvious morph‐specific differences were observed in wing venation, but wing allometry studies indicated that the distal areas of the fore‐ and hindwings were disproportionally reduced in the short‐winged morph compared to the long‐winged morph. The morphological differentiation of the wing pad between the two morphs was observed at the penultimate nymphal stage. The flight muscle was well developed in the two morphs, and no sign of flight muscle histolysis was detected in either morph after adult emergence. An analysis of adult body dimensions suggested that the density‐dependent phase shifts known for the long‐winged morph of this locust were also exhibited by the short‐winged morph, demonstrating that these shifts are not specific to the migratory long‐winged morph.