Colours of individuals are one of the more current morphological clues linked to overwintering adaptations. We studied morphological and physiological differences between colour morphs of Aphidius rhopalosiphi mummies in relation to possible adaptation to winter survival. Aphids Sitobion avenae were parasitised and placed in a controlled temperature room at 10[degree]C, under a photoperiod of L9:D15. Mummies were sorted by colour. Volume, fresh mass, water content, development time and cocoon thickness were recorded individually. Differences in development time were observed between dark and white forms, cocoon thickness and water content. We could not relate these difference to diapause status. However, these features are very likely linked to distinct cold resistance patterns and may be indications of a quiescence state. Whole animal physiology; Colour and luminescence; Colour; Evolution; Variation; Morphological variation; Abiotic factors; Physical factors Aphidius rhopalosiphi (Aphidiidae); Temperature relationships; Dormancy; Overwintering; Markings; Colour variation; Colour morphs; Mummies, correlations with overwintering adaptations; Temperature; Cold hardiness none