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).
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).
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).
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.
Embed this ARKive thumbnail link ("portlet") by copying and pasting the code below.