Habitat and Lifecycle
|Tansy beetle (Chrysolina graminis) © Steven Falk/Buglife|
Tansy beetles (Chrysolina graminis) are a specialist herbivore (plant eating) mainly eating Tansy (Tanacetum vulgare), a perennial herb, and complete their entire life cycle on and around the plant, beside riverbanks or in wetlands. Adult Tansy beetles are active around the tops of Tansy plants from April until June where they feed, mate, and lay eggs. They will be most obvious on warm, sunny days, and the female Tansy beetle is generally larger –bodied 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 tansy plants the pupae hatch in mid-July and can be seen on Tansy plants until September. They burrow underground and spend the winter there until emerging as adults in April.
|Tansy beetle larvae (Chrysolina graminis) © Steven Falk/Buglife|
The Tansy beetle was once widespread in Britain, but it is currently endangered, not just in the UK but across its worldwide range. It is now a UK Biodiversity Action Plan (UKBAP) priority species, which means that public bodies have a duty to protect it, together with its habitat. As the beetles are dependent on tansy as their sole food source, if a clump disappears the beetles have to walk to a new clump as they are not known to fly. Although Tansy is widespread, unfortunately pressures such as land-use changes and the increase of invasive species such as Himalayan balsam have resulted in a decline in Tansy plants over the past few decades. This has had knock-on effects on Tansy Beetle numbers as beetle populations have become increasingly isolated and can now only be found along a 30km stretch of the banks of the River Ouse, around York.
Tansy Beetle Action Group
A number of conservation efforts have been put into place to save this stunning beetle. The Tansy Beetle Action Group (TBAG) 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) and Yorkshire Wildlife Trust has undertaken a number of conservation measures to protect the Tansy Beetle with funding from the SITA Trust, York business 'Sumptuosity' and a legacy donation. These include:
- removing riverside willow and Himalayan balsam, which reduce Tansy growth
- planting Tansy clumps in large gaps to increase beetle movement, as they can only walk a maximum of 200 metres
- creating safe havens away from the river where beetle populations can be protected from summer floods, which cause high mortality
- reducing grazing pressure on Tansy by using short-term fencing and livestock management
- ensuring that during Ragwort control work, riverside land owners know the difference between Tansy and Ragwort
- yearly surveys to monitor populations
- captive breeding of the beetles and investigations into its reintroduction into the fens