Much of the following information was sourced from:
Influentialpoints.com, Myzocallis coryli Hazel aphid, Filbert aphid, Author unknown https://influentialpoints.com/Gallery/Myzocallis_coryli_Hazel_aphid.htm . Online. Accessed 20/11/2021
According to this source there are two species of green aphid commonly associated with Hazel (Corylus avellana) of which Myzocallis coryli is the more common and lives on the underside of Hazel leaves, which is certainly where we record it throughout the year. We are still attempting to get a photograph of the winged adult to confirm the species, but below is the nymph which most of us recognise as an aphid.
These guys hatch from fertilised eggs that over wintered on the hazel tree. It didn’t take us long to find some of the tiny black eggs nestled safely along a branch (see below).
They grow up to become winged females call ‘fundatrices’, which means adult females that developed from an overwintering fertilised egg. These fundatrice females give birth to live young (not eggs) which will develop into ‘viviparous’ aphid females. Viviparous aphids are all parthenogenetic, which means they can give rise to new young without requiring males. These will also develop into viviparous aphid females throughout the summer. We have also heard viviparous females referred to as Stem-mothers.
However come autumn this species needs to consider over wintering as a fertilised egg once again, and for this you’ll need some males. So it’s at this time of year the vivparous females give birth to ‘sexuparae’ aphids, which are aphids which will give birth to males and also egg-laying (as opposed to live young) females, referred to as ‘oviparae’.
The male sexuparae develop into adults with wings, the female oviparae a flightless adult, apparently in a ratio of 1 male to 5 females. Assumedly these mate resulting in the fertilised eggs that will now overwinter to become the following years fundatrices, and so the cycle continues.