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Eupeodes corollae - Vagrant Hoverfly

Eupeodes corollae is a very common European species of hoverfly. Larvae feed on aphids. This species has been used experimentally in glasshouses as a method of aphid control, and to control scale insects and aphids in fruit plantations. They were found to be partial to the fruit, eating more fruit than aphids.  E. corollae is found across Europe, North Africa and Asia. Adults are often migratory. 

Habitat: grassland, dune systems, dry river beds, garrigue, most sorts of farmland (including arable crops), suburban gardens, orchards, alpine grassland in the Alps. Hedgerows, grassy clearings in woodland, crops, gardens, tracksides, and road verges. 

The flight period is May to September (all the year in southern Europe) https://en.wikipedia.org/wiki/Eupeodes_corollae