Wednesday, 22 August 2018

Sawflies and Thorn Apple

Chris was at Northampton General Hospital today for the last of her course of treatments. The staff have been wonderful and the quality of care superb. As I have mentioned before the administration of her medication is a lengthy business and I usually take the opportunity to have a wander around the hospital grounds.

An unkempt rose near to the treatment rooms was looking tatty, stripped of much of its foliage. The culprit was not difficult to establish. It was a Large Rose Sawfly, Arge pagana. Confusingly there is another 'Large Rose Sawfly', Arge ochropus also going by the same name.

Arge pagana had defoliated much of a rose shrub in the Hospital grounds.
Northampton General Hospital, 22 August, 2018 
Northampton General Hospital has, for the best part of a century, been a site where Deadly Nightshade, Atropa belladonna, could reliably be seen.  Alas, the plants have quite understandably been sprayed and today I was unable to find a specimen.

Deadly Nightshade, Northampton General Hospital, 6 July, 2017
For all its toxic properties I hope that somewhere in the grounds some plants have survived. However, quite astonishingly, a matter of twenty feet from where I took the photograph above, I found what is possibly an even more toxic plant.

Thorn Apple, Datura stramonium, is a North American species from the same family, Solanaceae, as Deadly Nightshade. In America its dangerous properties have earned it the name of 'the Devil's Apple' although it is better known there as 'Jimsonweed', a number of American soldiers being poisoned by this plant at Jamestown in 1676. Its fruits look vaguely like an oval Horse Chestnut but the numerous seeds are dark and kidney-shaped.

Thorn Apple in the grounds of Northampton General Hospital.
22 August, 2018
I dug out my floras to find out more and I learn that the plant contains hyoscyamine, hyoscine and scopolamine. Here a little confusion sets in as I learn from Poisonous Plants and Fungi, (H.M.S.O 1988) that: 'poisoning...can be severe. Roman soldiers were poisoned by the plant around 38 B.C.'  A little research established that this 'North American' plant also occurs in North Africa, being found in parts of Algeria - an odd geographical distribution.

A closer look at the spiny fruit.
The leaves had been mined, apparently by the fly Pegomyia hyoscyami. This moth's association with Datura has not yet been noted in Britain although it is known from other members of the Solanaceae. Interestingly the specific name hyoscyami forms the generic name of Henbane, Hyoscyamus niger, a rare and also very poisonous relative of Deadly Nightshade and Thorn Apple.

Yet more strangely I recorded Pegomyia hyoscyami only yesterday, where it was mining the leaves of Swiss Chard (See my blog 'Dilly-dallying around Danetre'). All very odd. I ought to re-visit the hospital to procure a couple of the affected leaves. It is a thirty mile round journey: is that too far to go for scientific evidence?

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