Rhabdomiris striatellus

10 Tuesday Jun 2025

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British miridae, British plant bugs, bugs on Oak, insects on Oak trees, Miridae, oak tree, plant bug on Oak, Rhabdomiris striatellus

Here’s another bug that I’d never seen before this year and I’ve been lucky enough to find both a nymph and an adult. This is Rhabdomiris striatellus, one of the UK’s 200-plus species of plant bugs in the Miridae family. (I’ve probably only seen about a tenth of them so I’ve got plenty more discoveries yet to make.)

As this bug’s larvae feed on unripe catkins, it is usually found on or around Oak trees, and that’s certainly where I found the adult bug, shown below. The nymph above had probably fallen out of an Oak tree, or had decided to go walkabout to find a neighbouring Oak; I found it on the railings of my local park, where I’ve found so many invertebrates.

Rhabdomiris striatellus overwinters as an egg, hatches out in mid Spring, then passes through a series of instars until it reaches adulthood. The adults can then be seen from May through to July. Those timings certainly fit with my discoveries; I found the nymph on 25 April and the adult, in a different location, on 3 May.

Leafmines: Orchestes quercus

27 Monday May 2024

Posted by sconzani in insects, trees

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British leafmines, leafmine on Oak, leafmining weevil, oak tree, Orchestes quercus, weevil leafmines

During a wander along the woodland rides of Casehill Woods last Saturday, I spent some time checking Oak leaves for whatever creatures might be living amongst them. One of my finds was this leafmine, a new one for me, made not by a moth or a fly as most leafmines are, but by a weevil.

240527 Orchestes quercus (1)

A female Orchestes quercus weevil laid her egg in the central rib of the leaf (you can see the scar in the photo on the right, below). Once hatched, the larva munched its way down the side of the leaf rib, creating a thin gallery in the epidermis, before its more voracious feeding as it grew created a large blotch mine at the tip of the leaf.

240527 Orchestes quercus (2)

The UK Beetles website has a photo of the adult weevil, a tiny brown hairy creature around 3mm long. Although I searched for any weevils amongst the Oak leaves (I also found the larval mines of another weevil, Orchestes hortorum, formerly O. signifier), I found none.

Q is for Quercus

22 Wednesday Dec 2021

Posted by sconzani in leaves, trees

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galls on oak, moth larvae on Oak, Oak leaves, oak tree, Quercus species

When I began this alphabetical countdown, I thought I might struggle with some of the letters but Q was easy: Quercus, the Latin for Oak tree. The mighty Oak features often in this blog: its leaves for their autumn colours, for the galls they support, for the insect larvae they feed, for the birds that nest in the Oak’s branches, for the fungi that grow beneath this amazing tree … and so much more. This year, amongst other topics, we’ve had Oak leaf burst; a new gall I was lucky enough to find; and some mothy goodness. I’m sure the Oak will provide further wonders in the future.

211222 quercus

Oak: a new gall

25 Tuesday May 2021

Posted by sconzani in insects, leaves, spring, trees

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Andricus curvator, British galls, galls on Oak leaves, galls on oak trees, Oak gall wasps, oak galls, oak tree

With heavy cloud and occasional rain, Sunday was not a day for finding butterflies in the woodland. So, I decided to look more closely at Oak leaves to see what I might find, and that strategy paid off in spades as the next few days’ blog posts will show. First up, I found a gall I hadn’t seen before, which turns out to be the sexual generation of the gall wasp Andricus curvator.

210525 Andricus curvator (1)

When the adult wasps emerge in the spring from the agamic (asexual) generation galls, which are formed on buds in the autumn and fall to the ground to over-winter, they lay their eggs mostly on Oak leaves but also, sometimes, on twigs or catkins, so these galls can take several forms. The ones I found (and they were numerous) were all on leaves, causing malformations and swellings, as you can see from the photos above and below.

I was tempted to split a gall open to see what was inside but it turns out I didn’t have to, as something had nibbled away at one gall, revealing a second round gall inside (see below). The larvae within this inner gall will emerge in the autumn to lay its eggs on Oak buds, and so the process will continue.

210525 Andricus curvator (4)

Oak burst

14 Friday May 2021

Posted by sconzani in flowers, spring, trees

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British trees, Oak bud burst, Oak flowers, oak tree, tree flowers

Here’s the latest in my occasional series of watching the trees come to life. This time, it’s the Oak tree – I’m not sure which of the Quercus species this is but I think they’re all fairly similar. First, the leaves burst from their buds, and the vibrancy of the new growth is dazzling.

210514 oak burst (4)

And, of course, everyone knows acorns come from Oaks but perhaps, like me, you hadn’t noticed where the acorns come from. Below left are the male flowers, the catkins, dangling to catch the breeze that carries their pollen, and below right are the female flowers, tucked away, sheltered, waiting to be fertilised by the pollen and develop into acorns.

210514 oak burst (7)

200/366 Purple hairstreak

18 Saturday Jul 2020

Posted by sconzani in insects, nature, trees

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British butterflies, butterfly, butterfly in Oak trees, Cosmeston Lakes Country Park, Favonius quercus, Oak butterfly, oak tree, Purple hairstreak

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

Posted by sconzani in insects, nature, trees

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Chalcis wasp, Oak apple gall, Oak apples, oak galls, oak tree, parasitic wasp, Torymidae

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

Posted by sconzani in 365DaysWildin2019, nature, trees

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#365DaysWild, Oak, oak tree, Victoria Square Penarth, winter trees

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

Posted by sconzani in insects, nature, trees

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Andricus kollari, gall wasps, galls, galls on oak trees, Marble gall, oak galls, Oak Marble gall, oak tree

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

Posted by sconzani in insects, nature, trees

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Andricus kollari, gall wasps, galls on oak trees, hymenoptera in Oak marble galls, hymenoptera living in galls, Marble gall, oak galls, oak tree

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.

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.

171028 Wasp living in Oak marble gall (1)

171028 Wasp living in Oak marble gall (2)

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.