We have had one new species for the garden - a Grayling on July 24th. We see these on the rocky heathland on the edge of the Penmaenmawr quarry, not far as the crow (or chough) flies but 200m higher up than our garden at 100m.
Last year we had a few more exciting species in the garden, including a Small Pearl-bordered Fritillary and a White-letter Hairstreak (see photo). The former is a fast flier which could have come some distance from the nearest colony (wherever that is), while the Hairstreak is unlikely to have flown further than the elm trees across the road - elm is the food plant for this species. The white-letter is the W on the closed wings (hairstreaks at rest always have their wings closed).
We also record butterflies up the road, through Nant y Coed (our local Nature Reserve) and out onto rough grazing above. We do these weekly transects from April to September for Butterfly Conservation. The most exciting sighting this year has been a Dark Green Fritillary, a larger and even faster flier than the Small P-b species. On the debit side, I have failed to spot another species of hairstreak - the Purple, which lays eggs on oak leaves and also visits ash trees to feed on aphid honeydew. In previous years we've always seen these in July and August, but so far in 2011 not even a flash of purple.