Picture Wing Flies

In January 2002, members of the Al Ain chapter of the Emirates Natural History Group traveled to the Jazirah oasis to study the plant and insect life and to gather some oranges for the marmalade making competition.

In the course of the walk along the wadi, Brigitte Howarth came upon an oleander shrub and made a most interesting discovery: amid an infestation of insects was a small fly with decorated wings. The picture wing fly had established a symbiotic relationship with the ants which, in turn, had established a relationship with smaller insects which had infested the shrub.

Below is the announcement by Brigitte with a copy of a photograph.

What a wonderful oasis Jazira is - I'm enthralled every time I go there.

On the bug front, it was quite successful for both photography and collecting. I collected a variety of bugs, one of which is very fascinating and warrants to be highlighted. But first a little introduction.

On our walk along the wadi I stopped at an oleander shrub quite badly infested with very small scale insects. The shrub also had a variety of other insect life of interest, including some ants 'farming' another species of scale insect - a symbiotic relationship where both bugs benefit as the ants protect their 'flock' in return for milking the scale insects which produce a sweet honeydew excretion when tickled. The oleander also supported some leaf hoppers, solitary wasps, beeflies, and many others.

However, there was one insect which made me look twice. When I realised it was a fly I had to chuckle to myself as, sitting on a green leaf, the insect was barely visible apart from some darkening on the wings. The fly was small, approx. 6 mm in length with a grey-greenish body, iridescent green eyes, and clear wings apart from the darkening mentioned. On closer inspection the patterns appear to depict an insect! So, when the insect is sitting at rest on a leaf you see two small insects on the leaf rather than the fly!!! It's incredible how such a pattern would evolve but it obviously is of some benefit to the fly to be inconspicuous apart from its wings which sport insects. The protection could be to fool predators which might see the pattern but not the fly and thus give the fly some vital seconds to evade the predator.

Would this sort of protection be more beneficial to the insect in contrast to being totally inconspicuous? In my opinion yes, as some predators are very good at becoming specialised in foraging on one type of prey, even if this prey is trying to evade it. Thus, if the movement of the wings can give the prey species time to get away, it must be better than being gobbled up by a specialised predator!

By the way, the fly belongs to a family called 'picture wing flies' (Tephritidae). However, a wing 'picture', resembling an insect, I have not seen before today!!! The specimen now resides in our collection and will be on display for you to see in the near future.

Brigitte Howarth