From Nigel Spring –
This is part 2 of a four-part article. Since 2012 a team of volunteers and contractors working through EuCAN Community Interest Company and Butterfly Conservation has been working on the chalk downland sites between Lyons Gate and Godmanstone to remove the invading bushes and trees that are threatening to destroy the last vestiges of this incredibly biodiverse habitat in this area of Dorset. The plumes of smoke from the hillsides on Thursdays between September and March cannot have gone unnoticed.
Chalk downland is possibly the richest habitat in Dorset – one quick glance at the grassy sward on the slopes round the Cerne Giant will reveal perhaps a dozen obvious species of plants; if you look closely and count the species in a square metre you should be able to distinguish well over twenty, even thirty if you can identify the different grasses. They won’t all flower at once – the Cowslips, Early purple orchids and several violets tend to be first to bloom, while the vetches, Fragrant and Bee orchids and yellow dandelion-like flowers come out later and the Devilsbit scabious, Harebell, Clustered bellflower and Autumn hawkbit blooms signal the end of the summer.
Bee Orchids (Ken Dolbear)
Many of these plants are the caterpillar foodplants of the specialist butterfly and moth species that are so characteristic of this habitat. Blues like the Chalkhill and Adonis Blues need Horseshoe Vetch for their larvae; Birdsfoot Trefoil (sometimes called Eggs and Bacon) is the foodplant of the Common Blue, Dingy Skipper and the Burnet moths (those dayflying beetle look-alikes that buzz about the slopes in June and July)
Adonis Blue (male) Chalkhill Blue (male)
Small Blues favour Kidney vetch and the Duke of Burgundy Cowslip or Primrose leaves. One of the scarcest butterflies to be seen on the slopes of Giant Hill in May and June is the Marsh Fritillary whose caterpillars need Devilsbit scabious: the female lays her eggs in batches of 50-200 and the larvae live in crowded clusters on the leaves of the plants. In recent years this species has done very well on some of its local sites.
As well as being important for butterflies and moths, the chalk downland on Giant Hill also supports good populations of Glow-worms, specialist bee and wasp species (not the stinging sorts!) – including the beautiful little bee, Osmia bicolor, which lays its eggs in the empty shells of downland snails (featured in 2014 in a wonderful short film on the One Show), not to mention the many species of ants (one of which, the Yellow Meadow Ant, lives in colonies in the grassy mounds that are a feature of our ‘warty’ downland slopes).
Further information can be found on the EuCAN website http://www.eucan.org.uk/uk/dorset/cerne-valley-project/