Tag Archives: oak tree

200/366 Purple hairstreak

18 Saturday Jul 2020

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The key to where to locate this gorgeous butterfly, the Purple hairstreak, is in its scientific name Favonius quercus – quercus is the genus of the Oak tree – and I suspect that there are many more colonies of Purple hairstreaks living in our old Oak trees than we currently know about, as these butterflies spend much of their time unseen, high in the leafy boughs, feasting on honey dew.

200718 purple hairstreak (2)

There is a colony at Lavernock, and I’ve seen these butterflies at a couple of locations along the road that leads to Lavernock Point, but they were the only local sites I knew about. So, you can perhaps imagine my delight when, during Thursday’s walk at Cosmeston Lakes Country Park, I came face to snout with a female Purple hairstreak, which had ventured down to head height, and was happily running her yellow proboscis over the honey-dew-covered leaves.

200718 purple hairstreak (1)

This was the closest I’d been to one of these lovely creatures and had previously seen neither the purple sheen on their open wings nor the yellow proboscis. I was in butterfly heaven!

200718 purple hairstreak (3)

116/366 A gall and its parasites

25 Saturday Apr 2020

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This must be the largest Oak apple gall I’ve ever seen – it was at least 1½ inches across, and it had attracted the interest of several small wasps, though these are not the wasps that created the gall in the first place.

200425 oak apple gall

I assumed that they were parasitic wasps about to use their long ovipositors to inject their own eggs into the gall, and it turns out my assumption was correct. Thanks to the British Plant Galls account on Twitter (@BritGalls), and to another Twitter user’s tweet, I’ve learnt that the tiny wasp in the photo below is a member of the Chalcis genus of wasps, probably one of the family of Torymidae. They are ectoparasites: their larvae feed on the larvae of the Oak apple gall wasp that created the gall in the first place.

200425 parasitic wasp

41/365 Oak trees

10 Sunday Feb 2019

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190210 oak trees

I’ve been trying to find out how old these Oak trees are but haven’t managed it … yet. They grow on one side of the green that surrounds All Saints Church in Penarth’s Victoria Square. I did discover that the church itself dates originally from 1891, though it had to be rebuilt after being reduced to a burnt-out shell when 100 high explosives and 5000 incendiaries were dropped on Penarth during a bombing raid by the German Luftwaffe on 4 March 1941. I don’t know if the trees were also damaged in that bombing or whether they date from the 1890s … or even earlier. Whatever their age, they are magnificent.

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.

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)

 

Oak galls: marbles and apples

24 Thursday Aug 2017

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Though there are many more galls to be found on oak trees than the six I have covered in this and my previous two posts (knoppers and artichokes, and currants and spangles), I’ll make this the last lot for now. Otherwise, it might be just too galling for words!

170824 Andricus kollari Oak Marble gall (1)

So, to finish off this mini series, today we have Marble and Apple galls. Let’s start with the Marble galls and another tiny wasp, Andricus kollari, which lays its eggs on the twigs of any species of oak. This causes small perfectly round spheres to develop on these twigs. The spheres start off green but brown with age and will often remain on the twigs for a year or more. You can tell that the wasp has fled its larval home when you see tiny holes in the sphere. And although these do look just like brown marbles, I’m not sure you could use them to play the once-popular childhood game – they’re a little too light to shoot with.

And so to Oak apples. With their basic green colour and pink tinges, these do resemble immature apples but their surface texture and spongy feel are all wrong. The wasp Biorhiza pallida is the culprit this time, and these ‘apples’ contain several larvae, not just one.

Like many such wasps, both the Marble gall wasp and the Apple gall wasp have a sexual and an agamic (asexual) reproduction cycle. I have not seen the sexual galls produced by Andricus kollari which, interestingly, are produced only on Turkey oak (Quercus cerris) – the Marble galls are produced by the agamic (all female, no mating required) generation. Oak apple galls are produced by the sexual generation of Biorhiza pallida: the agamic generation lay their eggs on the roots of oak trees, so I haven’t seen those yet either.

170824 Biorhiza pallida Oak apple gall (1)

I find the whole concept of two different types of reproduction and, indeed, the way these wasps can cause such galls to form very intriguing!

Oak galls: knoppers and artichokes

23 Wednesday Aug 2017

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Following quickly on from yesterday’s oak galls, part 1, we have oak attack, part 2, a sorry tale of knoppers and artichokes – and, no, you can’t eat them!

First the knoppers, which are caused by Andriscus quercuscalicis, a wasp with chemical weapons. The wasp lays its eggs in buds on oak trees and the larvae, when they hatch, secrete a chemical that causes the developing acorn to distort into a knobbly lump, thus forming a home for themselves. The galls are structurally interesting but not so good for the oak tree, as the acorn is no longer a viable seed for the tree and I presume the knopper gall also makes the acorn unsuitable as food for wildlife as well. Apparently, this wasp only arrived in Britain in the 1960s but its spread has been rapid, with the galls now found throughout Wales and England and in southern Scotland, though only on the Pedunculate oak (Quercus robur).

Artichoke galls – also known as hop galls due to their resemblance to flower of the hop plant – are also the result of chemical distortion by a wasp. This time it’s Andricus foecundatrix that does the damage. Using its sharp ovipositor, it lays its eggs in the leaf buds of both the Pedunculate oak and the Sessile oak (Quercus petraea). Like yesterday’s Spangle-causing wasp, Andricus foecundatrix also has both a sexual and an asexual generation. The asexual wasp hatches from her artichoke home in the springtime and lays her eggs in oak catkins, causing a small oval-shaped gall to develop – I don’t yet have any photos of these galls but you can see images here.

Oak galls: Currants and spangles

22 Tuesday Aug 2017

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This is part one of the story of Oak galls – there will be a sequel (possibly two) because the poor old oak tree, one of the most iconic of British trees, the one almost everyone can identify, is also one of the trees most attacked by galls (though, in this case, the galls do little, if any, damage to the actual tree). This first Oak attack story is a bit like the chicken and the egg – which came first? – as Neuroterus quercusbaccarum, a wasp so tiny that only expert spotters ever actually see it, has the ability to reproduce both sexually and asexually, producing two types of gall on oak trees: the sexual generation is produced inside the Currant galls and the asexual generation develops inside the Common spangle galls.

Let’s start with the Currants. As their name suggests, they look a little like currants or berries, maturing in colour from yellow and green to red and purple. In spring, you can find these attached to an Oak’s catkins or to the undersides of leaves.

170822 Neuroterus quercusbaccarum Oak Currant gall

Inside, tiny larvae develop, emerging as adult wasps in June. These wasps are either male or female, they mate soon after emerging, then lay their eggs within the epidermis on the undersides of oak leaves.

Now to the Spangles. When the eggs of the Currant gall generation hatch and their larvae begin to develop within the oak leaves, they create Spangle galls on the undersides of those leaves. The galls look a little like inverted saucers, with a slight hump in the middle. They are hairy and often quite a bright pinkish red to begin with, maturing eventually to a dull brown. Once mature, in late summer, the spangles detach and fall to the ground to be covered by the leaves of the oak, when they fall in autumn. The larvae overwinter in their cosy spangles, hatching in the spring when, without the need to mate, they lay their eggs on the oak’s leaves and catkins, thus producing the alternate generation of Currant galls. And so the cycle continues …

170822 Neuroterus quercusbaccarum Spangle gall (4)