Violet Oil Beetle
Latin name: Meloe violaceus
Notable feature: Oil beetles are rather strange-looking beetles, their large abdomens protruding from under short elytra (wing cases) – they have been described as looking like some one whose waistcoat won’t button up!
Conservation Status: Least Concern
Where in the UK: Found throughout Britain, known strongholds include western Britain and Wales
Violet Oil Beetle (Meloe violaceus)
The Violet Oil Beetle (Meloe violaceus) is a native oil beetle in the UK. It is typically shiny violet in colour in England and Wales but can occasionally be black or bronze. It is very similar in appearance to the Black Oil Beetle (Meloe proscarabaeus), both have a square-shaped thorax, but the Violet Oil Beetle has an indented lower edge to the thorax. There is a depressed area at the base of the thorax and a strong tooth below the lower edge of the thorax, both of these features are absent in the Black Oil Beetle.
Male beetles have strongly kinked antennae, whilst the females have slightly kinked antennae.
The Violet Oil Beetle can be found in a variety of habitats including woodland edge habitats such as glades and rides, upland unimproved grasslands, heathlands, and on coastal cliff-top grasslands.
There are 5 species of oil beetle in the UK; 3 are rare in the UK (2 of these are listed as Vulnerable). A further 3 species of oil beetle have become extinct in the UK – Meloe autumnalis, Meloe cicatricosis and Meloe variegatus.
- Size: Adults can be up to 30mm in length. Beetle larvae are around 2mm in length.
- Life span: From egg to adult, approximately 1 year
- Diet: Adult oil beetles feed on the leaves and petals of flowering plants and grasses; favourites include Lesser Celandine (Ranunculus ficaria), soft grasses (Poaceae), Dandelion (Taraxacum officinale) and Cleavers (Galium aparine). Larvae (known as triungulins) feed on stores in solitary bee nests, including the pollen and the bee egg and/or larvae. After leaving the nest, triungulins are often found on Lesser Celandine and Dandelion, but will use other flowers.
- Reproduction: Oil beetles have one of the most extraordinary life cycles of any British insect – they are nest parasites of solitary mining bees. Females dig a short burrow into which they lay up to a thousand eggs. For Violet Oil Beetles, these eggs develop and hatch quickly, emerging later in the same season. Once these hatch the larvae (triungulins) climb to the top of the nearest flower and wait for a bee to arrive. They then grab onto the bee and hitch a lift back to its nest; the triungulin will then consume the pollen stores and either the egg or larvae of the bee. The triungulin will then stay in the bee’s nest, where it will pupate and emerge as an adult oil beetle when conditions are right the next spring.
- When to see: Adults can be found from March – June in woodlands, meadows and coastal grasslands throughout Britain. They are most active on warm, sunny days. Triungulins can be found from April to June.
- Population Trend: Declining.
- Threats: Oil beetles are reliant on solitary bees to compete their life-cycles. The health of oil beetle populations is therefore dependent on the health and diversity of wild bees. The wildflower-rich habitats that oil beetles rely upon have declined in quantity and quality due to intensive management of the countryside. Oil beetles are sensitive to changes in land management and are a good indicator of the health of our countryside.
- Fun Fact: The triungulins take 1 year to hatch from their eggs. This means that the triungulins found alongside the adults in spring are the larvae of the adults from the previous year!
How you can help:
Buglife is working to increase awareness of invertebrates and the Violet Oil Beetle through specific projects, such as Life on the Edge, Species on the Edge and campaigns, but we need your help!
Join a recording scheme and log your finds – send any records/sightings to the Oil Beetle Recording Scheme or download the iRecord app and get recording!
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