September 16th, 1998

During the past week, I have been looking closely at two of the yew trees which grow in the grounds. I have been able to do an estimate of the age of one of these trees by measuring the circumference of its trunk, calculating the radius and comparing with a slice from a yew tree that was knocked down by a lorry several years ago. This tree was 97 years old and had a circumference of 41 cm, indicating a radius of 6.5 cm. In the heartwood, there were an average of 18 growth rings per centimetre. The sapwood was, on average, 1.7 cm thick and contained 9 growth rings. The tree being studied had a circumference of 110 cm and I calculated its age to be around 290 years. Even if this tree has grown in slightly more favourable conditions than the comparison tree and is, therefore, younger than my estimate, it must have started growing at around the time that the Foundling Hospital which later became Ackworth School was built.

In recent weeks, I have received a number of reports from local people who have found 'huge, brown caterpillars' with 'eyes'. I have have seen three of these caterpillars - two brown and one bright green - and have identified them as caterpillars of the elephant hawk moth. This is a moth that I do see from time to time but the caterpillars seem to be especially numerous this year. The eyes referred to are, presumably, the colourful markings on the body. The actual head of the caterpillar is very small in relation to the body and is retracted when the caterpillar is disturbed. It is normal for the caterpillar to be represented by these two forms.

Amongst the horse chestnut cases which have fallen from trees in the grounds, there are ones which have been opened by grey squirrels. The squirrels do not have a neat way of opening the cases but chew away many small fragments until they reach the contents. These fragments can be seen scattered around what is left of the empty cases.