Six-Spot Burnet Moths at Llangennith

The distinctive black and red markings of this daytime-flying moth make it easy to see and recognise. When I made a Gower visit in August, I saw dozens of these moths as I walked along the fenced board-walk from Hillend Campsite to the beach through the sand dunes of Llangennith Burrows.

Unusually, these moths were all coupling. The photograph above shows two Six-Spot Burnet Moths (Zygeana filpendula) in the act of mating. They are in a wonderful fresh condition. The wings are intensely black with an almost metallic sheen – contrasting with the vivid red spots. The various species of Burnet Moth are partly differentiated by the number and arrangement of the spots.

The adult moths (or imagos) had all recently emerged from the pupal stage. The couple pictured above have settled on one of the many brown papery cocoons that the caterpillars (or larvae) had built for the metamorphosis to pupa (or chrysalis) stage. Normally these cocoons are built on the upright stems of tall grasses or similar vegetation. In this instance, a great number had also been spun on the vertical strands of a wire fence.

When the development to the adult insect has been completed within the pupa, the pupa wiggles around in the cocoon until it tears it open. The pupa partly emerges from the shelter of the cocoon. The skin of the black pupa then splits to allow the adult insect (that has been folded inside it) to crawl out into the open air. The wings are all crumpled at first but the moth pumps fluid into the veins of the wings to flatten and straighten them out. The empty pupal skin is left poking out of the cocoon.

The colours and patterns on the wings are partially the result of light reflection on many minute scales that cover the wings. With time, as the moth flies around, these scales rub off and the colours fade. In the picture below, of an adult feeding on a yellow flower at nearby Whiteford Burrows, the light shines through the spotted fore wings which are translucent with the loss of scales and it is possible to see the red hind wings beneath.