Aphids usually overwinter on roses as eggs laid on the stems in the previous autumn. However, in sheltered places there may be active nymphs and adults all year round.
Aphid numbers start to increase in spring when roses are producing new growth and reach a peak in early summer. Some rose aphids are green but a common species, Macrosiphum rosae, is pink. During spring and summer, the aphids are mostly wingless forms, 2-4mm long, that give birth to live young.
Winged forms develop when plants are heavily infested and aphids need to migrate to new host plants.