Burdock Gall Flies

This year I have been keeping a watch out for great burdock in the hope of seeing the burdock gall flies that I saw last year.  However, there was no sign of it in the places where it grew last summer and I was beginning to give up hope.  Then, a few days ago I noticed a burdock plant on the dam at the lower end of the middle lake.  It was infested with black aphids so I got down and had a closer look and then I noticed that there were also little yellow flies on it.  On getting my photos back home I found that these flies were probably Tephritis bardanae (Diptera: Tephritidae) which are similar but not identical to the Terellia tussilaginis that I saw last year (see here and here).

I have noticed before that Tephritidae sometimes flap one wing at a time, as if they are signalling by semaphore:

Photos taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2010-06-19.

Comments

[P Coward]

Hi Tristram, I've just Googled 'semaphore fly burdock' and got through to your fascinating blog. I studied Zoology at Reading in the sixties and remember Whiteknights Park well. It looks as though my signalling flies are Terellia tussilaginis. I took a closer look at the Burdock this morning because the tops of the buds had been eaten out, leaving dark holes. Then I noticed the little flies exploring the holes and jerking their wings. Many thanks for sharing your discoveries and photos online.