TANSY BEETLE

Chysolina Graminis

Chrysolina graminis.jpg

A spectacular, large, green leaf beetle, with a distinctive coppery sheen.

  • Rarity: It is restricted to a 45km stretch of riverbank centred on York, as well as two small areas in the Cambridgeshire Fens
     

  • Causes of decline: This species is dependent on Tansy along the River Ouse, which is becoming more scattered due to changes of land use and competition with invasive plants.

The Tansy beetle is an iridescent green leaf beetle that is affectionately known as the Jewel of York. This beautiful beetle is roughly 1cm long - about a quarter of the size of a one pence coin. The Tansy beetle was once more widespread in Britain, but this striking beetle is now restricted to the banks of the River Ouse (near York) and small areas of the Cambridgeshire Fens. The declines in this beetle’s population and restricted location means it is a conservation priority and so is listed as Endangered (at risk of extinction) on the national Red List of threatened species.

The banks of the River Ouse near York are a nationally important area for this beetle, where a large proportion of the British population is found. Therefore, it is important that the banks are in part managed for the beetle and its York food-plant, Tansy. Tansy Tanacetum vulgare, with its yellow button-like flowers, is a common riverside plant that often grows in clumps. 

​Threats to the beetle on the Ouse, include:

  • Tansy uprooted when mistaken for Ragwort Senecio jacobaea

  • Tansy and beetles eaten by high numbers of grazing animals

  • Tansy clumps over-shadowed by willow or out-competed by the invasive plant Himalayan balsam Impatiens glandulifera

  • Mowing the riverbank when the beetle is vulnerable (March to October)

  • Bank erosion and summer flooding

When planning riverbank management it is important to consider any work in conjunction with the beetle’s life cycle. The beetle is particularly vulnerable during the reproductive phase of its life cycle i.e. between March and September. Cutting and other operations that remove Tansy plants should be avoid during this time.