Yet another hoverfly to add to our growing list of species for the valley Xanthogramma stackelbergi its recently been added to the british list in 2012 and closely resembles the more common Xanthogramma pedissequum. I also think its a first for Glamorgan. The key features have all been checked and confirmed by expert Joan childs on the UK hoverflies website, i've posted photo's showing all the key features that were on the hoverfly below. The hoverfly was in long grass at the bottom of bramble at the old sewage works site at the old St john's colliery Cwmdu.
The dark wing does not extend down below R2 + 3
On this image you can clearly see that the membrane between tergites and sternites segments 3 and 4 is clearly yellow which is consistant with this species on pedissequum you would expect to see dark shading on the membrane and you can just about see that the lateral edges of yellow bands slightly pinched on sides
Here you can clearly see that the yellow triangular spots are rounded to slightly pointed on the inner side.
The side of thorax usually has more than 3 spots but couldn't get a full side on view of the thorax to be 100% sure but there's enough evidence on the other key features to confirm ID.