Parthenogenesis produces clones of individuals very rapidly and this is obviously an advantage but aphid colonies do not go on reproducing themselves indefinitely. At a certain time clonal reproduction ceases and males and egg-laying females appear, mate and produce fertilised eggs. You can see a male (winged) on the rose bud greenfly colony
The last two days were very cold and overcast in Cambridgeshire and this Four-spotted Chaser emerged on Monday morning and was still in the same position on Tuesday until mid afternoon when the wind turned more southerly giving a bit of warmth. The irises are full of exuvia -6 or 7 so far this year.