Tag Archives: gall wasps

268/366 Gone galling

24 Thursday Sep 2020

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I wanted a relatively short walk between rain showers so headed to a small local green belt where Oak saplings were planted a few years ago, and my wander turned into a challenge to see how many different types of gall I could find in just this one small copse of young Oaks. The answer? Six!

200924 oak galls (1)

First up, Knopper galls, caused by the wasp Andriscus quercuscalicis. For more on that gall, see my August 2017 post Oak galls: knoppers and artichokes.

200924 oak galls (2) knopper

Next, Marbles, which I covered in Oak galls: marbles and apples, August 2017.

200924 oak galls (3) marble

Then, I found some Common spangles (below left), caused by the wasp Neuroterus quercusbaccarum. More on that mouthful in Oak galls: currants and spangles, August 2017.

You may have noticed my photo of Marble galls also had something else on the leaves. These were Smooth spangles (above right), a product of the wasp Neuroterus albipes.

I covered both Smooth spangles and this next gall, the Oyster, in the same blog: Oak galls: spangles and oysters, September 2017. The photo on the left above shows Oysters just beginning to form on the spine of the leaf; the one on the right shows two more developed examples, both on the same tree.

200924 oak galls (6) silk button

And, last but most certainly not least, as there were thousands of these on all the Oak trees I looked at, Silk button galls, caused by the wasp Neuroterus numismalis. I wrote about those in Oak galls: ram’s-horns and silk buttons, September 2017.

Not a bad haul for an hour turning over leaves and peering amongst branches. I didn’t find examples of all the Oak galls I’ve found before but I was very happy with this sampling.

137/366 Bedeguar gall wasp

16 Saturday May 2020

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You might remember that, a few months ago, I posted about the (supposedly) empty galls of the Bedeguar gall wasp I’d found during a wet walk at Cosmeston Lakes Country Park (Empty pincushions, January 2020). A week or so after writing that post, I was back at Cosmeston and remembered to harvest one of the galls, which has ever since been sitting in a sealed jar on my kitchen windowsill.

Although the many holes in the gall made me think that all of its inhabitants had already hatched, I decided to wait and see if anything else appeared. Two days ago I noticed movement in the jar and, taking a closer look, found two different species of wasp had emerged.

200516 diplolepis rosae (1)

This is one of them, and I’m 99% certain this is the gall causer itself, the Bedeguar gall wasp, Diplolepis rosae, the offspring of the wasp that caused the gall to form in the first place. These wasps are so tiny – just 3-4 mm long – that most of us don’t usually see them so I was very pleased to have this one emerge from its gall.

200516 diplolepis rosae (2)

There is a bit of a story attached to the second wasp that emerged, and I am currently awaiting confirmation of its identity. As soon as I know more, I’ll write it up in a further post.

31/366 Empty pincushions

31 Friday Jan 2020

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Robin’s pincushions are the amazing gall structures created on Dog roses by the larvae of Diplolepis rosae, the Bedeguar gall wasp.

200131 Robins pincushions (1)

I’ve seen the bright red galls many times during the summer months but I’ve not looked for them in the winter, so it was interesting today to find these and to see the very obvious holes where the adult wasps have hatched out. If it hadn’t been raining, I would have broken one off and brought it home for a closer look inside … maybe next week.

200131 Robins pincushions (2)

155/365 A good crop of apples

04 Tuesday Jun 2019

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190604 oak apples (1)

But you wouldn’t want to eat them! These are oak apples, the incredible creations of the larvae of the wasp Biorhiza pallida. By a magical process of chemical interaction, the larvae force the buds of the Pedunculate Oak to change and produce these galls, which the larvae call home until they’re ready to develop into their next stage of life.

A couple of the young oak trees in some fields near where I live are proving particularly attractive to these wasps so they have a bounty of apples growing on them this year. Yet another of Nature’s miracles!

190604 oak apples (4)

Andricus kollari, maybe

14 Saturday Apr 2018

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180414 Andricus kollari (3)

If you’re a regular around here, you may recall that in August 2017, I posted a mini-series of posts about some of the galls you can find on Oak trees, which included the Oak Marble gall (see the post here). You might also remember that in late October, I was excited to discover a creature had hatched out of one of my galls and I initially thought it was the gall causer, a minute wasp called Andricus kollari. It was not – turns out it was one of the 29 other species of hymenoptera (bees, wasp, ants and sawflies) that can also be found living in an Oak marble gall (more on that here) (and I never did identify it).

Well, this time, maybe, just maybe, I have seen the gall-causing wasp itself, A. kollari. A while ago, while out walking, I found a small Oak sapling that was absolutely covered in marble galls and, when I found one that had no holes in it, I couldn’t resist bringing it home. The tiny wasp you see in these photos recently hatched out of this gall and the size of the hole it made, plus comparisons with online photos, has led me to think that this time I may have seen the gall causer. I couldn’t be one hundred percent certain of my identification without killing the wasp and getting an expert to check it but I didn’t want to do that. And, of course, I could be totally wrong yet again. In the meantime, the wasp has been returned to the area where I found it so, weather permitting, it can continue its life cycle.

Wild words: Inquiline

08 Wednesday Nov 2017

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I learnt this word the day a mystery wasp hatched out of an Oak Marble gall I’d brought home. Though I thought it must be the gall-causing wasp, it turned out that it was not and could, in fact, have been any one of 29 other species of hymenoptera that can, potentially, make their home in a Marble gall. According to an article I found on the Natural History Museum website (‘Oak-galls in Britain’ by Robin Williams), 21 of those other gall inhabitants are parasitoid (their larvae consume the original gall wasp’s larvae) and 8 are inquiline, which is to say that they are simply ‘exploiting the living space of another’ creature. And the Oxford Dictionary online actually gives the instance of ‘an insect that lays its eggs in a gall produced by another’.

171108 Oak marble gall inhabitants (1)

Of course, if I’d been smart and compared the size of the holes in other Marble galls I have to that of the newly emerged creature, I would’ve twigged that they must be quite different. I’m afraid my curiosity then got the better of me and I sliced in half one of the Marble galls I had, which means that the little creatures I exposed will not survive. The larva (and large hole) in the centre is the gall wasp Andricus kollari, and the little larvae and holes are representatives of the other 29 possibilities.

Lesson – and new word – learnt, I have now returned to the wild the other various galls, of several kinds, that I’d brought home thinking they were empty, in case they also have little creatures growing inside them!

Life in an Oak Marble gall

28 Saturday Oct 2017

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Back in August, as part of a mini-series on some of the galls to be found on Oak trees, I posted about the Marble galls caused by the incredibly tiny wasp, Andricus kollari. Although most of the galls I’ve found have had tiny holes in them, meaning the wasps had already pupated and flown, a couple of weeks ago I found a couple with no holes. So, my curiosity got the better of me and I brought them home to see what might eventuate.

171028 Oak marble gall

Note the tiny creature sitting on the gall.

Today, when I looked in the jar I’d put them in, I was so excited to see a tiny creature had appeared. Now, I initially thought this must be A. kollari, the gall-maker, but I was wrong … and, looking at images online, I don’t think I’m the only one who’s ever been fooled by this. However, with the help of friends who questioned and strangers who know much more than me, I’ve discovered there are at least 29 (twenty-nine!!) species of hymenoptera (bees, wasp, ants and sawflies) that might live within an Oak marble gall.

Though some of these critters simply use the gall for shelter, it seems that, for others, the gall tissue is a good source of nutrients, while still others are parasites whose larvae kill some or all of the larvae of the original gall-making wasp. Without detailed microscopic examination, I’m not able to determine which species this tiny wasp is but I thought you might like to see this little video of it performing its ablutions earlier. I have now released it back in the area where I found it so let’s hope it survives.

Oak galls: ram’s-horns and silk buttons

18 Monday Sep 2017

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I can’t resist just one more post about oak galls, because I’ve just this week found one that’s not commonly recorded. So, today we have one that’s uncommon and one that’s very common. Let’s start with the former.

First identified in eastern Europe in 1859, the Ram’s-horn gall wasp, Andricus aries, has slowly been heading westwards and finally reached Britain in 1997. Since that first sighting in Berkshire, it has spread over much of southern England and into Wales. Though there are only a few records in the Aderyn database of Welsh biological records, two of my friends have also found Ram’s-horn galls in the past week so I suspect it’s more common that records suggest.

Like other gall-inducing wasps, Andricus aries lays its eggs on various species of oak and its larvae cause the oak to produce a gall, in this case with an elongated, sometimes spiralling shape, hence aries and its common name Ram’s-horn. Not much is yet known about this wasp, so if you see the gall, please do record it.

170918 Neuroterus numismalis Silk button gall wasp (3)

My second gall today is one many people will have seen, I’m sure, as its beautifully crafted silk-like button-shaped galls are very common on the undersides of oak leaves during the summer months. This gall contains the agamic generation (females needing no males to reproduce) of the Silk button gall wasp, Neuroterus numismalis. The galls fall to the ground in autumn and the larvae within pupate over the winter months. When the all-female wasps emerge in springtime, they lay their eggs on the edges of oak leaves and on the male catkins, where their larvae cause a different blister-shaped gall – that’s another one for me to seek out next spring. It is the female and male wasps of this second, sexual generation produced in the Blister gall that go on to mate and lay the eggs that result in the silk buttons. And so the cycle continues …

Oak galls: spangles & oysters

09 Saturday Sep 2017

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I know you’re all just dying to find out more about oak galls, right? RIGHT? I also know that I covered spangles in a previous post (see Currants & spangles here) but there are two different spangle galls to be found on the much be-galled oak tree: one is the hairy Common spangle and this is the second, the Smooth spangle gall.

170909 Smooth spangle gall (1)

This pretty little gall comes in combinations of pink and yellowish-green. It’s the work of Neuroterus albipes, a tiny wasp that you will probably never see, and inside each colourful saucer is a single larva that you will also probably never see. The galls drop to the ground in autumn and the larvae pupate over winter then female-only wasps hatch out in Spring to lay eggs that cause the entirely different Schenck’s gall (not one I’ve yet seen), from which male and female wasp hatch in the summertime. And so the cycle begins again.

This second gall, the Oyster gall, is also caused by a tiny wasp that has two distinct generations and forms two different galls. The wasp is Neuroterus anthracinus and the Oyster gall also contains the agamic generation of wasps (i.e. the females that need no males to fertilise their eggs). As you can see, these galls form on the veins on the undersides of oak leaves – once they’ve fallen to the ground, you can still see the two brown flaps of tissue where they were attached to the veins. 

Once again, the sexual generation of wasps hatch in the Spring to mate and lay their eggs, this time in the buds of the oak tree, hence the name of the gall they produce: the April-bud gall. That’s another I need to look out for come the Spring.

170909 Oak Oyster gall (3)