Around April each year, depending upon the weather, the endangered Tansy Beetle which is a large, iridescent green leaf beetle, with a metallic sheen, appears above ground. Adult Tansy Beetles become active for the first time in the year from April until June where they feed, mate, and lay eggs. They appear to be most obvious on warm, sunny days.
The female Tansy Beetle is generally larger than the male. The eggs hatch between May and July into larvae, which feed hungrily on tansy leaves. The larvae eventually burrow underground at the base of the plants and the pupae hatch in mid-July, when they can be seen on Tansy plants until September. They burrow underground again and spend the winter there until emerging as adults in April.
Tansy Beetles (Chrysolina graminis) are a specialist herbivore (plant eater), mainly living on the tansy (Tanacetum vulgare) plant, a perennial herb although a number of other wetland plants such as apple mint, water mint and gypsywort are believed to support them. The Tansy Beetle was once widespread in wetlands and river valleys in Britain, but it is now endangered, not just in the UK but across its worldwide range. It is now a conservation priority species in England (a ‘section 41’ species), which means that public bodies have a duty to protect it, together with its habitat. Although once widespread, they are now only found along the banks of a 30 Km stretch of the River Ouse, around York. As the beetles are dependent on tansy as their primary food source , if a clump disappears the beetles have to walk to a new clump as they don’t seem able to fly, [all beetles have wing cases and nearly all have wings – they just don’t work in some species!]. There are clearly some habitat issues that have limited the beetle to York but what the combination of factors leading to their loss nationally is unclear. The availability of the food plant, soil conditions, predation by other species may all have an impact, as will flooding, grazing and other management factors.
The Friends of Rawcliffe Meadows are a member of the Tansy Beetle Action Group (TBAG) which is made up of Buglife, North Yorkshire County Council, the City of York Council, the Environment Agency, the University of York, the National Trust, BIAZA (Zoos Association), The Deep, Leeds City Council and the Yorkshire Wildlife Trust. The Group has undertaken a number of measures to protect the tansy beetle.
At Rawcliffe Meadows we have increased the number of plants available to the beetles, focussing on areas that we have seen them survive on. This means controlling grazing , ensuring that maximum sunlight reaches the plants, having them on slightly raised areas to reduce the effects of summer flooding and cutting back other invasive vegetation. We are also experimenting with having other potential food plants available for the beetles and larvae and observing their behaviour.
Oxford, G., et al, (2003), The Jewel of York – Ecology and Conservation of the Tansy Beetle, British Wildlife, June 2003
Chapman, D.S., et al, (2006), Ecology of the Tansy Beetle in Britain, Naturalist, 131
Chapman D.S., et al, (2007), Modelling population redistribution in a leaf beetle: an evaluation of alternative dispersal functions, Journal of Animal Ecology, 76, 36-44
Chapman D.S., et al (2007), Landscape and fine-scale movements of a leaf beetle: the importance of boundary behaviour, Oecologia, November 2007, Volume 154, Issue 1, pp 55-64