August saw some sightings of Adonis Blue butterflies on Therfield Heath. These butterflies haven’t been seen in Hertfordshire since 1959.
It is not clear how they came to be seen on site as they are not a butterfly that travels great distances and their nearest stronghold is some way away. They were not introduced by either the Conservators of Therfield Heath and Greens or by Butterfly Conservation. If introduced, it was done illegally and in breach of the SSSI regulations.
“This is a warmth-loving species, preferring sheltered, south-facing slopes. This species is found where the turf is closely-cropped, possibly because it provides a higher temperature for the immature stages or because this is a requirement for the ant species that attend the Adonis Blue larva and pupa. The loss of grazing by rabbits, for example, causes the sward to become overgrown and can render a site unsuitable for this species. ” from UK Butterflies.
For more detailed information on this species, visit Butterfly Conservation.