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Tag Archives: Oak apples

116/366 A gall and its parasites

25 Saturday Apr 2020

Posted by sconzani in insects, nature, trees

≈ 6 Comments

Tags

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

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155/365 A good crop of apples

04 Tuesday Jun 2019

Posted by sconzani in 365DaysWildin2019, insects, nature, trees

≈ 2 Comments

Tags

Biorhiza pallida, gall wasps, galls, galls on oak trees, Oak apples, oak galls, Pedunculate Oak

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.

190604 oak apples (2)
190604 oak apples (3)

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)

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Oak galls: marbles and apples

24 Thursday Aug 2017

Posted by sconzani in insects, nature, trees

≈ 4 Comments

Tags

Andricus kollari, Biorhiza pallida, gall wasps, galls on oak trees, Marble galls, Oak apple galls, Oak apples, oak galls, Oak marbles, oak tree

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.

170824 Andricus kollari Oak Marble gall (2)
170824 Andricus kollari Oak Marble gall (3)

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.

170824 Biorhiza pallida Oak apple gall (3)
170824 Biorhiza pallida Oak apple gall (2)

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!

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sconzani

sconzani

I'm a writer and photographer; researcher and blogger; birder and nature lover; countryside rambler and city strider; volunteer and biodiversity recorder.

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