Tag Archives: galls

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.

A mini challenge

09 Monday Oct 2017

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On Friday I went for a wander around one of my favourite local haunts, Cosmeston Lakes Country Park and, while there, I set myself a little challenge. How many critters could I find in one small area, perhaps no more than 2 metres square?

171008 mini challenge

My challenge wasn’t pre-planned: I had seen very little at this point on my walk and was thinking to myself that this was due to autumn and the cooler weather but, when I saw a Speckled wood butterfly at this particular spot – a bank covered with shrubs and small trees – I started wondering how much more there was that I simply wasn’t seeing. So, I stopped and looked harder. There was no poking under grasses or bushes, no sweeping or brushing to encourage movement, just focussing my eyes and ears to really see and hear.

There were, in fact, three Speckled woods – I just hadn’t noticed the other two, plus three different species of spider (the Garden spider was lunching on another critter but it was partly consumed and too tiny to identify), one hoverfly, three species of flies, a gall on Bramble that would’ve been home to the larvae of the tiny gall wasp Diastrophus rubi, and a leaf mine, made by the larva of some unidentified mini-beast. And I’m absolutely sure I didn’t spot everything!

More galls, part 2

04 Wednesday Oct 2017

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Following on from yesterday’s More galls, part 1 …

This second gall’s host is not a tree, it’s a thistle, Creeping thistle (Cirsium cardui) to be precise, and the gorgeous little fly that causes the gall is Urophora cardui, the Thistle gall fly, a member of the Tephritidae or fruit fly family. Interestingly, this fly has been introduced into Canada, from populations originating in Austria, Germany, France and Finland, in an attempt to control Creeping thistle, which is there called Canada thistle and is regarded as an invasive weed. The gall production initiated by the flies disrupts the development of flowers and also significantly reduces the vigour of the thistle by diverting nutrients into the gall.

In Britain, the adult Urophora cardui fly can be seen between May and September when, after mating, it lays its eggs on a nearby Creeping thistle. The larvae burrow into the thistle’s stem, often causing a single gall to develop to house several larvae. The larvae also pupate inside the gall, emerging as flies between June and October. I’ll be checking all the Creeping thistles I see for a glimpse of them.

More galls, part 1

03 Tuesday Oct 2017

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Today’s and tomorrow’s galls are not on the gall-beleaguered Oak tree and, for a change, they are not caused by wasps, as so many galls seem to be. These two galls are caused by tiny members of the enormous order of flies, the Diptera.

171003 Iteomyia capraea on Salix capraea (1)

Today’s is Iteomyia capraea (sometimes known as Cecidomyia salicis-folii) (Cecidomyiidae is the family name for gall midges or gall flies). I think I would need better specs to actually see the midge that laid its eggs on this Goat willow (Salix caprea) leaf as it’s only 2-3mm long. Indeed, the galls themselves were pretty small (5-8mm), as you can see from the leafy picture below. When they hatch, the larvae of the midge feed within the leaf tissue causing the willow to develop a gall, sometimes on the midrib of the leaf, sometimes on a thick side vein. I’ve read one report that the larvae are white, another that they are an orange-red colour but I didn’t open up any of the galls for a look at the larva inside so I can’t confirm either report.

I’ve not been able to discover much about Iteomyia capraea. There are only 215 records showing in the NBN (National Biodiversity Network) database for the whole of Britain, 45 of which are in Wales, but I think that is more a reflection on the under-recording of galls that the rarity of the midge itself. Apparently, the species only breeds a single generation per year and they hibernate over winter in the soil underneath their host tree.

One of Nature’s whodunnits

22 Thursday Sep 2016

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I sometimes get asked how I come up with enough ideas to post a blog every single day. This post goes some way to explaining how it works for me. I walk … a lot, and my camera is my constant companion, and I am by nature curious about … well, everything, really … and I’m also quite an observant person. So, for example, I went out for a wander around one of my local parks on Monday afternoon, thinking I would see if there were any fungi about, and also to get some photos of berries for a future blog. In the process of taking those photos, I noticed how many galls there were on this one particular oak tree so also took some photos of those … which then led me to check the neighbouring trees for galls. (If you’re not sure what galls are, there will now be a blog post on them as well!)

160922-whodunnit-1

When I got home and started going through my photos, this particular image really grabbed my attention because, for me, this is such a good example of one of Nature’s whodunnits. I look at this and my brain is immediately flooded with questions: how were these galls made? Why are they that shape? What is the creature that’s dead on the leaf? Is it a wasp? Did it make the galls? What killed it? It looks like it has white strands around it – a spider’s web or some kind of fungus? What created the bare patch where the leaf’s veins are showing? Was it the larvae of the wasp? What created the almost perfectly round hole in the leaf? Was that a leafcutter bee or something else? Was it the wasp? And what is the teeny weeny white thing? The shed skin of a larva perhaps?

I don’t know the answers to any of these questions … yet. But, if I find out and if I can get more images related to the story, the result could be a blog or three from just this one photo. And so it goes on …