Monday, 13 August 2012
A walk along the River Thames
Took Coco for a walk along the ‘Riverside Walk’ this morning. Really liked the talking post, very informative.
Looking west to the three wind turbines at Fords of Dagenham.
Came across a Buddleja davidii with a few small tortoiseshell along with peacock butterflies feeding on it. I remember seeing loads of these during my childhood.
The Small Tortoiseshell is one of our most-familiar butterflies, appearing in gardens throughout the British Isles. Unfortunately, this butterfly has suffered a worrying decline, especially in the south, over the last few years.
This butterfly has always fluctuated in numbers, but the cause of the most-recent decline is not yet known, although various theories have been proposed. One is the increasing presence of a particular parasitic fly, Sturmia bella, due to global warming – this species being common on the continent. The fly lays its eggs on leaves of the foodplant, close to where larvae are feeding. The tiny eggs are then eaten whole by the larvae and the grubs that emerge feed on the insides of their host, avoiding the vital organs. A fly grub eventually kills its host and emerges from either the fully-grown larva or pupa before itself pupating. Although the fly attacks related species, such as the Peacock and Red Admiral, it is believed that the life-cycle of the Small Tortoiseshell is better-synchronised with that of the fly and it is therefore more prone to parasitism.