Dasineura fraxini galls

03 Wednesday Nov 2021

Posted by sconzani in insects, leaves, trees

Tags

Ash tree galls, Dasineura fraxini, gall causing midge, gall midges, galls, galls made by midges, galls on Ash leaves, midge gall

One of the benefits of checking the leaves of various trees, and other plants, for leafmines is that, even when I don’t find them, I do find other things just as interesting, and this is one of those. I didn’t know what it was, of course, until I got home and checked my Field Studies Council Guide to plant galls in Britain fold-out guide. (If you’re not familiar with these, check the FSC online shop here. I have a few of these and find them really useful.)

My guide informed me that these galls on the leaves of Ash trees were created by the larvae of Dasineura fraxini, a species of tiny midge. Few people have ever seen the adult midge but I did have a look at one of the galls that was partly open and spotted one of the miniscule orange larvae. These galls can be found from May through to October, at which time the leaves will fall to the ground, where the larvae will pupate and over-winter until emerging as adult midges in the springtime.

211103 Dasineura fraxini (3)

More galls, part 1

03 Tuesday Oct 2017

Posted by sconzani in insects, nature, plants, trees

≈ 4 Comments

Tags

Cecidomyia salicis-folii, gall flies, gall midges, gall on Salix caprea, gall on willow, galls, Iteomyia capraea

Today’s and tomorrow’s galls are not on the gall-beleaguered Oak tree and, for a change, they are not caused by wasps, as so many galls seem to be. These two galls are caused by tiny members of the enormous order of flies, the Diptera.

171003 Iteomyia capraea on Salix capraea (1)

Today’s is Iteomyia capraea (sometimes known as Cecidomyia salicis-folii) (Cecidomyiidae is the family name for gall midges or gall flies). I think I would need better specs to actually see the midge that laid its eggs on this Goat willow (Salix caprea) leaf as it’s only 2-3mm long. Indeed, the galls themselves were pretty small (5-8mm), as you can see from the leafy picture below. When they hatch, the larvae of the midge feed within the leaf tissue causing the willow to develop a gall, sometimes on the midrib of the leaf, sometimes on a thick side vein. I’ve read one report that the larvae are white, another that they are an orange-red colour but I didn’t open up any of the galls for a look at the larva inside so I can’t confirm either report.

171003 Iteomyia capraea on Salix capraea (2)

171003 Iteomyia capraea on Salix capraea (3)

I’ve not been able to discover much about Iteomyia capraea. There are only 215 records showing in the NBN (National Biodiversity Network) database for the whole of Britain, 45 of which are in Wales, but I think that is more a reflection on the under-recording of galls that the rarity of the midge itself. Apparently, the species only breeds a single generation per year and they hibernate over winter in the soil underneath their host tree.