Seasonal and diurnal variation in the proportions of female morphs of the damselfly Enallagma cyathigerum

In many damselfly species a female-limited colour polymorphism is encountered which is assumed to be the result of sexual conflict. Typically, one morph resembles the male’s body colouration (andromorph), while the other is dissimilar (heteromorph). Little is known about the extent of temporal variation in female morph proportions at the water, were mating occurs. Knowledge on such variation should help to identify the factors that affect female morph proportion and the scales at which these factors operate. Here, we assess the occurrence of diurnal and seasonal variation in female morph proportions at the water for the damselfly Enallagma cyathigerum. Diurnal variation was evaluated at six locally nearby populations; while seasonal variation was examined at one of these populations. Further we considered temporal variation in female morph proportion in relation to proxies of male harassment (i.e. male density and sex ratio). Our findings indicate female morph proportion to vary throughout a day, but to be constant on a seasonal scale. Variation in female morph proportions could not be explained by concomitant variation in male density or sex ratio. We suggest future study of male mate choice may consider temporal variation in female morph proportions at the water.