Flies do not have nymph stages. Egg, several instars of larva, pupa and adult. Judging by the poor degree of melanization, I'll suggest a newly emergent adult.
Flies are Diptera = one pair of flight wings and the other pair reduced to haltere balancing organs. I see two obvious pairs of wings so Hymenoptera is a possibility.
I did not say it was a fly. I said it was a Barkfly nymph
http://www.brc.ac.uk/schemes/barkfly/introduction.htm
Psocoptera are an order of insects that are commonly known as booklice, barklice or barkflies. They first appeared in the Permian period, 295–248 million years ago. They are often regarded as the most primitive of the hemipteroids.
https://en.wikipedia.org/wiki/Psocoptera
Here is an adult from the same location but I have no idea if it is the same species.
Barkfly by Alf Branch, on Flickr