Oil Beetles

There are four species of oil beetle in the UK, the Black oil beetle (Meloe proscarabaeus), Violet oil beetle (Meloe violaceus), Rugged oil beetle (Meloe rugosus), Short-necked oil beetle (Meloe brevicollis). These four species have been identified as priorities for conservation action through the UK Biodiversity Action Plans – meaning work needs to be done to protect them and their habitats. Buglife is working on an oil beetle conservation project to find out more click here.

Have you seen an oil beetle?

As part of the oil beetle conservation project Buglife are hosting an Oil beetle survey. There are only four species of Oil beetle found in the UK and Buglife are asking you to take a photo and submit your record if you think you have seen one! Click here to take part.

Oil beetle life cycle

Oil beetles have some of the most extraordinary life cycles of any UK insect. They are parasitic on various species of ground nesting solitary bees. The female lays lots of eggs to ensure that at least some larvae will make it to an adult stage.

Adult oil beetles can live for up to five months and feed on the leaves of various plants such as grasses, buttercup and lesser celandine. Female oil beetles are considerably bigger than males and become much larger when carrying eggs. The females excavate a small burrow or burrows in sandy soil near nesting aggregations of solitary mining bees and lay up to 1000 eggs! Eggs hatch and the oil beetle larvae – called triangulins - emerge to coincide with the emergence of the bee hosts.

Triangulins – young Oil beetles

The newly hatched triangulins are extremely active and rapidly climb onto vegetation in search of flowers. On the flower heads many larvae will congregate, waiting for a bee to visit the flower. The triungulins attach themselves to a visiting bee using their specially adapted hook-like forelegs. If the bee is female and a suitable species, then the larvae will be carried back to the bee’s nest burrow.

Once inside the bee’s nest, the triungulin changes into an entirely different larval form and begins to feed on the bee’s egg and pollen store. The larvae grows rapidly on such a sugar-rich source of food and after undergoing three more moults it pupates and overwinters in the bee burrow before emerging the following year as an adult oil beetle.