Footballer hoverflies are commonly seen near water: ditches, ponds and drains, their genus name Helophilus, actually means 'lover of marshes' in Greek. On a little twig over a puddle on the pavement by a busy road, two Helophilus pendulus females - their abdomens large and turgid with eggs - laid. While one of them was busy actually laying under the twig, the other seemed to be 'feeling' the twig with the ovipositor, probably selecting the best site to lay her shiny white eggs. Note the ovipositor stretched out. Helophilus lay their eggs on clumps - like bluebottles - unlike other hoveflies which lay individual eggs singly. This might well be due to their different feeding habits. Many hoverfly larvae are predatory, and being born away from hungry siblings might give them a better chance to find food (like aphids). Helophilus are related to Droneflies, and their larvae, called rat-tailed maggots, are aquatic, and develop on very wet manure or submerged rotting organic material often in large numbers, so they are less likely to compete for food. Their 'tails' are actually long telescopic breathing tubes, that they can retract into their bodies.
For a great series of shots of Helophilus egg laying and larvae development check BugGuide.
Another shot of the laying female
I turned the twig to reveal the egg clutch after the female lad left. As they lay under the twig, the eggs are not readily visible.