K is for Knopper

16 Saturday Dec 2023

Posted by sconzani in insects, plants, trees

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British galls, bug galls, galls, galls on Ash, galls on Hazel, galls on oak trees, galls on Poplar, galls on willow, galls on Yew, Knopper gall, midge galls, mite galls, wasp galls

This is really a review of the galls I’ve found this year but the letter G simply had to be about my first ever confirmed Goshawk sighting, so K is for Knopper is my alternative lead in.

231216 Knopper Andricus quercuscalicis

Knopper galls, like the one shown above, did feature in one post this year, Acorns and galls on 1 October, but there were many other galls, most of which were new finds for me. February saw the year off to a good start with galls on Yew trees caused by a tiny midge (Galls: Taxomyia taxi, 9 February) and galls on Hazel caused by an equally tiny mite (Galls: Phytoptus avellanae, 20 February). In June, it was a small bug that was creating eye-catching galls on the leaves of an Ash tree (Galls: Psyllopsis fraxini, 12 June), and, in July, aphids were the gall causers on a Poplar tree (Galls: Pemphigus spyrothecae, 17 July). In that October blog Acorns and galls I mentioned above, as well as the knoppers, another tiny wasp had caused artichoke galls to form on the same Oak tree. And, a couple of weeks later, I found my final new galls for the year, those caused by midges on Willow trees (Galls: Rabdophaga rosaria, 17 October). All in all, 2023 was quite a galling year!

231216 mixed galls

Galls: Phytoptus avellanae

20 Monday Feb 2023

Posted by sconzani in insects, trees

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British galls, bud galls, gall mites, gall-causing mites, galls on Hazel, Hazel, mite galls, mites, Phytoptus avellanae

These are my latest gall finds, caused by the mite species Phytoptus avellanae, shown here on Hazel (Corylus avellana) though they can also affect the buds of Filbert (Corylus maxima). The feeding of the mites on the plant cells within the buds causes those buds to swell and multiply. You can see a comparison in my photo below, the mite-infected gall bud on the left, the normal bud on the right.

230220 gall Phytoptus avellanae (1)

The mites that cause these galls are tiny, so rarely seen, but the Dutch Bladmineerders website has some excellent photos showing them in minute detail. As with so many galls, they are thought to be widespread in Britain but are not well recorded. So, if you’re out and about enjoying a spring walk and spot some Hazel, do please cast an eye over the buds, and record any galls you see. Citizen scientists really do make a difference to our knowledge of the natural world around us.

230220 gall Phytoptus avellanae (2)

On narrow-leaved willows

26 Monday Dec 2022

Posted by sconzani in fungi, insects, leaves, trees

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Aculus tetanothrix, Euura proxima, hoverfly larva, insects on narrow-leaved willow, ladybird pupa, leafmines on narrow-leaved willow, mite galls, moth eggs, Phyllonorycter viminiella, rust on willow, sawfly galls

In early October I, and others, began a new leafmine search, for mines on narrow-leaved willows (see Leafmines: Phyllocnistis saligna, 3 October). In the months since, I’ve only found these mines in two locations, partly due to a lack of the host plants and partly, probably, because the moths have yet to spread very far (which may be because of a lack of host plants). I’ll continue the search next autumn but, in the course of my search – and this is one of the brilliant things about staring at leaves – I’ve found many other life forms that were making these leaves their home.

221226 on willow (1)

I found two types of galls: the first, above top, have been made by a species of mite, Aculus tetanothrix, and those immediately above are home to the larvae of the sawfly species, Euura proxima.

221226 on willow (2)

On the underside of one leaf I found this array of what I think are moth eggs and, on the right, is the pupa of a ladybird, and, below those, is a hoverfly larva.

221226 on willow (3)

There was also a different species of leafminer, the tiny moth Phyllonorycter viminiella, and I found a rust, which might be Melampsora caprearum.

Holm oak gall mites

09 Wednesday Feb 2022

Posted by sconzani in insects, trees

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Aceria ilicis, British galls, gall mites, galls, galls on oak trees, Holm oak, mite galls, mite galls on Holm oak

During yesterday’s walk, when checking for leaf mines on the leaves of Holm oak (large numbers of Ectoedemia heringella present – you can see one in the photo below), I noticed a huge abundance of small bumps covering many of the leaves.

220209 Aceria ilicis on holm oak (1)

These are the galls caused by the miniscule mite Aceria ilicis. On the underside (though sometimes also on top), the depression in the leaf is filled with tiny brown hairs (an erineum) where the mites make their home. The galls can be seen throughout the year, so next time you spot a Holm oak, check out its leaves.

302/366 Gone galling, again

28 Wednesday Oct 2020

Posted by sconzani in autumn, insects, leaves, trees

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Aceria macrochela, gall mites, gall-causing mites, galls, galls on Field maple, galls on Spindle, mite galls, Stenacis euonymi

October is a good month to check out life on leaves (and I’ll be writing some posts about the various leaf mines I’ve been finding) but today I want to show you a couple of gall species that are new to me. The first is quite common and easy to find, the second perhaps less so.

The first species is Aceria macrochela, a microscopic mite that spends its larval life in these tiny bumps on the leaves of Field maple (Acer campestre). You can read more about them and see more images on the mighty Nature Spot website.

And the second is also a mite, this one called Stenacis euonymi, whose larvae make their homes in the rolled-up edges of leaves on Spindle (Euonymus europaeus). If you have trouble with tree identification, as I often do, this is a good time to look for these as the gloriously obvious fruit of the Spindle are easy to spot.

201028 Stenacis euonymi (1)

Looking on the NBN (Nature Biodiversity Network) Atlas I see there are currently only 112 UK records for this species (113 including mine, which doesn’t show yet) but that’s probably due to it being under-recorded, so if you spot these, please do record your sighting.