Sounds very like leatherjackets, they feed in midsummer eating the roots of the grass ,therefore your grass will recover slightly until then, they are the young of daddy long legs, and the eggs are laid under the grass, they do leave holes in the grass,where they burrow out, and usually attack newly cultivated areas, it's probaby worth treating the area with a preparation from the garden centre to avoid this happening again this summer, I had the same problem last year and had no idea what caused it until an experienced gardener visited and told me about leatherjackets. Hope this helps