Rainbow leaf beetle (Chrysolina cerealis)

The rainbow leaf beetle is arguably one of the most beautiful beetles in Britain. Its common name refers to the longitudinal bands of green, purple and red on the wing cases or 'elytra' ⁽⁴⁾. Males are generally smaller and more slender than females ⁽²⁾.

Size

Length: 5.5 - 10 mm ⁽²⁾

Both larvae and adults feed on wild thyme, and show a preference for the flowers. Larvae have been found during the day on plants growing in crevices, and beneath stones ⁽³⁾. Adults are present from April to September, and eggs are laid during June. It is thought that the larval stage overwinters, as larvae have been found in September and October, but young adults may also overwinter ⁽⁵⁾.

Despite exhaustive searches, there are few known populations of this beetle, although it is difficult to find ⁽³⁾. In the UK, this endangered beetle is currently known only from Caernarvonshire in Wales; since 1980 it has been recorded from Snowdon and Cwm Idwal. Elsewhere the species is found in northern, central and southern Europe ⁽³⁾.

You can view distribution information for this species at the National Biodiversity Network Atlas.

This beetle is found in mountainous grassland areas over 630m above sea level ⁽³⁾. Populations are localised to areas where flushing produces base-rich grassland characterised by an abundance of wild thyme in the sward ⁽⁵⁾.

Classified as Endangered in the UK and protected under Schedule 5 of the Wildlife and Countryside Act, 1981 ⁽³⁾.

There is no evidence that this beetle has undergone a decline; it may be that it has always been scarce. The threats facing this species are not clear, but many montane invertebrates are thought to be at risk from climate change ⁽³⁾.

The rainbow leaf beetle is a priority species under the UK Biodiversity Action Plan (UK BAP), and is protected under schedule 5 of the Wildlife and Countryside Act, 1981 ⁽³⁾. Cwm Idwal and Snowdon are National Nature Reserves, and so receive a degree of protection. The Snowdon population of this beetle is being monitored by the Countryside Council for Wales (CCW), and the Institute of Terrestrial Ecology is using this beetle as part of an investigation into the effects of climate change on montane invertebrates ⁽³⁾.

The UK Biodiversity Action Plan for this species is available at UK BAP.

View information on this species at the UNEP World Conservation Monitoring Centre.

The UK BAP Species Action Plan for the rainbow leaf beetle is available on-line from:
http://www.ukbap.org.uk

Information authenticated by Adrian Fowles of the Countryside Council for Wales:
http://www.ccw.gov.uk

Elytra

In beetles and earwigs, the hard fore wings. They are held aloft when the insect flies, and are often coloured or patterned.

Larvae

Stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

1. National Biodiversity Network Species Dictionary (Jan 2003): http://www.nhm.ac.uk/nbn/
2. Harde, K. W. (2000) A field guide in colour to beetles. Silverdale Books, Leicester.
3. UK BAP Species Action Plan (March 2003): http://www.ukbap.org.uk
4. Joy, N. H. (1949) British beetles: their homes and habits. Frederick Warne & Co Ltd., London.
5. Buse, A. (1993). Life-cycle and behaviour of the British population of Chrysolina cerealis (Coleoptera: Chrysomelidae): the implications for survival. Entomologist, 112: 105-117.