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Tag Archives: gall causing midge

Dasineura fraxini galls

03 Wednesday Nov 2021

Posted by sconzani in insects, leaves, trees

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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.)

211103 Dasineura fraxini (1)
211103 Dasineura fraxini (2)

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)

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316/366 Green islands

11 Wednesday Nov 2020

Posted by sconzani in autumn, insects, trees

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Tags

beech, gall causing midge, galls on Beech, green islands, green islands on Beech leaves, Hartigiola annulipes, leaf mines, leaf mines on Beech, Stigmella tityrella

It’s late autumn, nearly winter, and, as you would expect, the leaves on this Beech tree have all now changed from vivid summer green to autumn brown … or have they? If you look more closely at this image, you’ll notice that some of the leaves have what entomologists, moth-ers and others in the know call ‘green islands’.

201111 green islands on beech

Butterfly Conservation’s Associate Director of Recording and Monitoring Richard Fox explained the reason for this most succinctly in a recent post on Twitter: ‘Thanks to Wolbachia bacteria in its body, the caterpillar uses cytokinin to maintain a green island of plant tissue in which it can feed in autumn.’

201111 green island stigmella tityrella (2)
201111 green island stigmella tityrella (1)

Fox was referring to leaf-mining moth caterpillars, like the Stigmella tityrella moth larvae that produced the mines in the leaves shown above, but other insects also manipulate the physiology of leaves so they can continue feeding. Another example from the same Beech tree can be seen below – here the larvae of the gall-inducing midge Hartigiola annulipes have also caused green islands to form in the leaves.

201111 Hartigiola annulipes green islands (1)

If you want to read more on the science behind this process, I found a paper entitled ‘Plant green-island phenotype induced by leaf-miners is mediated by bacterial symbionts‘, on the Royal Society website.

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About me

sconzani

sconzani

I'm a writer and photographer; researcher and blogger; birder and nature lover; countryside rambler and city strider; volunteer and biodiversity recorder.

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