Hi Tony,

Sounds like "mosca negre" or to us foreigners, black fly, they are a damned pest, especially on the fincas.
You can spray all of the finca to keep them at bay, but the best thing for us, is to take loads of garlic capsules.
A local family told me about the Natural Honey body lotion, which is also very effective, you can find it in most supermarkets and Shlecker shops.

Hope this helps.

Jools