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Keywords:

  • Syrphidae;
  • Eristalis;
  • phenotypic variation;
  • phenotypic plasticity;
  • colour variation;
  • seasonal variation

Abstract.

  • 1
    An examination of phenotypic variation in colour pattern was carried out on four Eristalis hoverfly species using museum material.
  • 2
    The amount of phenotypic variation varied substantially among the species with E.arbustorum being the most variable. The other species showed a wide colour pattern range but less variation within that range (E.abusivus and E.nemorum), or a narrow range of colour variation (E.horticola).
  • 3
    Sexual colour dimorphism was apparent in all four species, but most pronounced in E.abusivus and E.nemorum.
  • 4
    There were good phenotype-season relationships shown by both sexes in all species, except for female E.abusivus and E.nemorum, with paler insects being more abundant during the warmer summer months.
  • 5
    Female, but not male, E.arbustorum collected at inland sites were on average paler than those collected at coastal sites. This observation is considered with respect to temperature during the developmental stages.
  • 6
    The function of colour plasticity in hoverflies is discussed with reference to the need to maintain optimal thermal conditions for activity.