Infestation by the Small Ermine Moth Yponomeuta padella on the Blackthorn of Port Gaverne Main

Malcolm Lee

In Spring 2003, all the Blackthorn near the Headlands Hotel on Port Gaverne Main was covered in webs, and thousands of black caterpillars were all over the bushes. The infestation covered an area of several hundred square metres, probably involving many hundreds of thousands of larvae. They were the caterpillars of the Small Ermine Moth Yponomeuta padella, a common UK moth but not often seen in such numbers to completely defoliate the plants.

Although a very common species, surprisingly, it has only been recorded once before in nightly monitoring of our local moths over the last 10 years. They are probably migratory, and some must have settled on the blackthorn a year or two ago. There were no larval webs noted last year, so just small numbers were probably present in 2002.

Only after the larvae had pupated at the beginning of June was the blackthorn able to keep the green leaves it has been sending out since the spring. Despite this complete defoliation, it is unlikely that any long term harm has been done to the plants.

The adult moth started to emerge towards the end of June, to start the life cycle again. They are about 10mm long, and are really quite pretty with their silver wings covered in tiny black dots. It is likely that the population will crash in another year or so, as future generations of larvae will literally eat themselves out of house and home. Click on the thumbnail pictures below for larger versions.

There was  a conservation day On Saturday March 1st.  It started at 10.30 am with an introduction from Chalie David, Coast and Countryside Officer for North Cornwall District Council. There were opportunities to learn about the fauna and flora of the Main and to help with the management of the blackthorne.
People brought gardening tools, like rakes and chopping implements and had a good (if rather wet) time. 

Malcolm Lee's book on the flora and fauna was given as a token of appreciation of the work. 

We have formed a small conservation group from this event and will be planning future work over the coming year.

Thumnail Photos below - double click to see bigger versions

Port Gaverne and the area around it is classified as an "Area of Outstanding Natural Beauty" .For general records of the natural history of Cornwall a very useful site is The Environmental Records Centre for Cornwall and the Isles of Scilly (ERCCIS) run by the Cornwall Wildlife Trust. It aims to collect records of all land, freshwater and marine plants and animals that live or have lived in Cornwall and the Isles of Scilly. It also aims to provide an information resource for research, education, survey work and environmental monitoring.The computerised archive contains over a million records of some 22,000 species.

The main source of information about the Natural History of Port Gaverne, and the Main itself will be in the heads of the people who live there plus a few people who have made a study of this area themselves. One in particular is a Parish Counsellor, Mr Malcolm Lee. His publication 'The Flora and Fauna of Port Gaverne North Cornwall was written as a report for the National Trust in 1992 and 1993, and then published as a booklet with drawings by Carole Lee.

It covers the following types of animals and plants
Wild flowers, ferns and grasses
Birds
Seashore and Offshore
Insects
Reptiles and Amphibians
Mamal
In addition in the appendix it has locations of scientific interest, a checklist of wild flowers, a seabird survey and other things. One thing that caught the imagination was the discovery of some stick insects which are described here.

For information about stick insects Malcolm Lee has written a short account which appeared in the journal Phasmid Studies in 1993. Right-click here for the article using 'save target as..':

Marine biology sites can be found here:

Marine Fauna online
The National Marine Aquarium Plymouth
The Plymouth Marine Laboratory