The influence of environmental factors on wing polymorphism in females of Leptopterna dolobrata (Heteroptera, Miridae).

Abstract

The females of Leptopterna dolobrata (Heteroptera, Miridae) occur either as flightless brachypters or as macropterous individuals, whereas all the males are longwinged and capable of flight. The expression of this alary dimorphism is influenced by both genetic and environmental factors. Population density and temperature conditions prevailing during larval development both affect the formation of macropterous females. The larval instars L4 and/or L5 are particularly sensitive to these environmental stimuli and are thus decisive for the determination of wing-morphs.Experimentally crowded larvae developed a greater proportion of macropterous females than individuals reared at lower densities, and lower temperatures seem to counteract the stimulating effect of crowding. Larvae from different local populations varied in the proportion of macropters which developed, which could be ascribed to differences in the genetic constitution, although the genetic basis of wing-morph determination in L. dolobrata is not yet understood.There is strong evidence that in crowded populations a high percentage of the emerging macropterous females will emigrate and perform dispersal flights to new habitats. The sexual maturation of macropterous females is retarded compared with the brachypterous morph, and the dispersal flights are likely to occur during the pre-reproductive period.The underlying physiological mechanism of wingmorph determination and the adaptive significance of its environmental control are discussed on the basis of information available from other polymorphic species.