Nature on our Doorstep – The ‘bee-grabber’ fly

Nature on our Doorstep – The ‘bee-grabber’ fly

By Rosaleen Dwyer

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into the natural heritage around us and the beautiful biodiversity of the plants and creatures

An interesting species of fly was recently recorded for the first time in Tymon Park. 

With its bands of light yellow and black, this fly looks very wasp-like. It has only 1 pair of wings though, unlike wasps which have 2 pairs.

The Red tailed bumble bee is the main target for the bee grabber fly 1

The Red-tailed bumble bee is the main target for the 'bee-grabber fly'

It is one of the group of flies known as Conopids, and while this particular fly does not have a regularly used common name, it is sometimes referred to as a ‘thick-headed fly’.  This is due to the relatively large size of its head.

It has also been referred to as the ‘bee-grabber fly’ because of what it does to unsuspecting Red-tailed bumble bees. 

The fly sits patiently on a flower, waiting for a bumble bee to fly past. 

When one arrives, it launches into the air and grabs the bee. In mid-flight, the fly quickly lays an egg in the bee’s body before releasing it again.

While it looks wasp like the Conopid is a species of fly. 1

While it looks wasp-like, the Conopid is a species of fly

On hatching inside the unfortunate Bumble bee’s body, the fly’s larva lives as a parasite. It feeds on the nutrients in its host’s body until the bumble bee finally dies. 

The fly’s larva then makes use of the empty bee corpse by spending the winter in the carcass.  It uses it as a pupa (cocoon structure), where it develops into a new adult fly, emerging the following spring.

An interesting fly indeed. 

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