This article relates to a small area of acid grassland situated between the Mountview Road overbridge and the Blythwood Road entrance gate, this small parcel of land is the only one of its kind along the Walk, or indeed in the whole of Islington.
Nationally, south facing habitats of this kind are in jeopardy, with the loss of associated plants and other wildlife. In this particular example, due to the gradual encroachment of surrounding trees, the overall area has shrunk. The annual leaf-fall continues to raise nutrient levels within the grass and reduce acidity. Although this may sound like a good thing, in fact it means a loss of plant diversity. Acidic grassland plants such as Sheep’s Sorrell are being lost, which in turn effects the fast flying Small Copper butterfly, a beautiful insect whose numbers are going down in the country as a whole.
In addition, as the sward gets richer, it also becomes more uniformly covered and, as a consequence, less species rich. This seriously affects a great many other species of insect.
One, in particular is well worthy of mention – a parasitic ‘cuckoo-bee’ (Nomada lathburiana), being on the Red Data List for London and designated ‘rare’ in the Capital. Nomada species look more like wasps than bees. Crucially for the Nomada, its host the ‘mining – bee’ (Adrena cineraria) prefers a sunny, vegetation sparse habitat where it prepares a nest by burrowing into the ground. The Nomada female follows the Adrena and lays her eggs on top of hers. When the cuckoo bee larva hatches it consumes the host larva's pollen ball, and the host larva.
The Acidic grassland is also home to another interesting insect – a largish dark brown ant (Formica cunicularia). Recorded locally early in the 20 Century by E.A Butler in a book called ‘British Ants, their life histories and classification’, compiled by Horace Donisthorpe. It is fascinating to consider that we may well be looking at the same colony today.