Long-legged Fly
Condylostylus ?
Alighted on a weed within a maize field at Eldoret, Kenya, July 2014. Length is about 5 mm. The larvae breed, perhaps, in the thatch following harvest and the adults such as this one might be predators of small maize-feeding bugs. Thus they are possibly beneficial and certainly not a maize pest.
From Wikipedia: the long-legged flies, make up a large family of true flies with more than 7,000 described species in about 230 genera distributed worldwide. The genus Dolichopus is the most speciose, with some 600 species. They are generally small (this one is 5mm) flies with large, prominent eyes and a metallic cast to their appearance, though considerable variation is observed. Most have long legs, though some do not. The adults are predatory on other small animals.