The Migrant Hoverfly Eupeodes corollae is a typical black and yellow hoverfly. Males and females have different shaped yellow spots - males are rather square and sometimes joined, females are crescent shaped. The side edges of the abdomen are mostly yellow.
A mating pair in our garden, April.The adults are 5 - 8 mm long and are on the wing between March and November. Numbers peak in July and August. They are found on flowers on the margins of arable land, meadows, road verges, hedgerows, heaths, gardens and waste ground in both rural and urban settings. One of the commonest hoverflies of open habitats, and abundant in some years.
For full details of how to identify this species, go to British Hoverflies by Stubbs and Falk or the Diptera.info forum.