Nature on our doorstep: Picture-wing flies

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into nature on our doorsteps and the beautiful biodiversity of its plants and wildlife.

The ‘Picture-wing’ flies are so named because their clear wings are patterned with black stripes or with patches of brown or black dots.

They belong to the large group of Fruit Flies.

One particular member of this group is the Hogweed Picture-wing fly.

This fly is widespread over much of Europe, North Africa, and central Asia.

They occur wherever its host plant, Hogweed, grows, so they can be found along hedgerows, in damp meadows, parks, and even in gardens.

A close look at this fly reveals its beautiful patterns and colours.

Its wide wings have bands of broad black lines set against a clear background, and it has stunning, shiny green eyes.

The fly is unusual in that the colour of its body varies depending on the season.

Summer flies have an orange-brown body while the winter flies have a black body.

In summer, the Hogweed Picture-wing fly has an orange-brown body.

The male of this species can sometimes be spotted in April and May displaying his wings on the host plant.

He will parade back and forth across the large leaf with his wings held up and out to the side, hoping to attract a female.

Following mating, the female fly lays her eggs inside the Hogweed leaf, in the very narrow space between the leaf’s top and the bottom surfaces.

The eggs hatch out after about a week, and the tiny larva begin to feed on the plant cells that make up the narrow space.

As it grows and develops, the larva ‘mines’ out a tunnel through the leaf middle, and this tunnel eventually turns brown and blotchy.

When it is mature, the larva leaves its tunnel home and makes its way down the stem of the Hogweed to the soil below.

It makes a burrow and it continues its development there throughout September and October.

Because they can feed on celery, this species of picture-wing fly is also known as the Celery Fly.