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.

Wild words: Inquiline

08 Wednesday Nov 2017

Posted by sconzani in insects, nature

≈ 2 Comments

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#WildWords, Andricus kollari, gall wasps, hymenoptera living in Marble gall, Inquiline, Marble gall, oak galls, Oak Marble gall

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!