Manuscripts and Special Collections

Gall Wasps!

May 27th, 2010 at 08:05

Earlier today I had a group of children visiting Conservation from a local primary school. I had a number of things out to illustrate the work that goes on in Conservation.

  Alongside an 18c document I had a bag of ‘oak apples’. These were to illustrate what type of ink was used in the document. Oak apples are often used in the preparation of Iron Gall ink, mixed with iron filings (ferrous sulphate), beer, wine and honey – even urine has been known to have been added to the concoction. This fermented brew gives a dark black and permanent ink (very useful for legal documents).

But I stray from the story, the children on closer inspection could see that one of my apples had hatched and there was a fully formed adult wasp in the sealed bag along with the apple it had eaten its way out of! The adult wasp lays its egg in the bark of an oak tree, the tree then grows to form the apple around the developing wasp grub which feeds the insect until it is ready to fly away. The apples don’t seem to harm the tree, but do produce a useful by-product of oak apples with a high tannin content that have been used in ink for hundreds of years.

You (and the visiting children) may be pleased to know, the wasp was released into the wild following the visit.

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