  
Askham BogSunday 9th July 2000
  DURING THE LAST ICE AGE the snout of a glacier dumped a crescent of debris to the east of present-day Tadcaster. This long, low, embankment of debris is known as the Escrick Moraine.The glacier 'retreated' and left another end moraine, the York Moraine, a short distance to the north. York is sited where the River Ouse cuts through this moraine.
The Narrow Buckler Fern is yellowish green and has fronds that are a similar width all the way up the stem. It has kidney-shaped sori (spore producing bodies) on the underside of some of its fronds.
The caterpillars feed on the leaf buds of the oak.  
There's a colony of Ringlet butterflies along a shady woodland ride. These butterflies seem to me to have a slow motion flight as they make there way at grasstop level. There's something a rather dreamlike in the way they're flying on such a dull day in a sheltered ride. It seems along way from the bright sun, the brilliant flower borders and the crazy, out of control flight, you might associate with butterflies.   Two Peppered Moths are mating on the grassy edge of a woodland ride. They are both the melanistic form. In the 1960s, this species was often cited as an example of the kind of process that might lead to a new species evolving. According to the story, observations suggested that the black form was becoming more common, especially in industrial cities. It was suggested that, as lichen-covered trees gave way those with bare, smoke-blackened trunks, the regular peppered variety were increasingly picked off by birds. These two seem to be doing well, but I don't see any smoke-blackened trees in the immediate area, or any lichen-rich trees, come to that. I wonder if the black form has any advantage in being able to warm up more quickly on a dull day?
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After some 15,000 years of erosion, not to mention the action of meltwater streams at the time, these moraines aren't dramatic features, but they still affect the drainage of the area. This is why, when you turn off the A64 into York, pull up at a small rough parking area, then walk down a track past the edge of a golf course, you will suddenly find yourself in a little wilderness the Yorkshire Wildlife Trust Askham Bog Nature Reserve.
I'd forgotten how persistent Mosquitoes could be, but it was worth suffering a few bites to see the plantlife, which today included Common Spotted Orchid, Milkweed, Marsh Pennywort, Meadow Rue and Narrow Buckler Fern, and the insect life which included Meadow Brown, Ringlet and, a first for me, the Purple Hairstreak butterfly.
The Purple Hairstreak is amongst the herbage in a small damp clearing below Alder and Oaks. This is a female, with small patches of iridescent purple forewings against a dark brown background. In males the purple almost covers the forewings and extends to the hindwings.