One of the most conspicuous insects found on cliff paths and in meadows in Spring is the Black Oil Beetle (Meloe proscarabaeus). This flightless insect is so named because it emits a pungent, oily substance when alarmed, and has one of the most extraordinary life cycles of any British insect.
Oil beetles are nest parasites of solitary mining bees. Female oil beetles dig nest burrows in the ground, in to which they lay hundreds of eggs. Once hatched, the active, louse-like, larvae climb up on to flowers and lay in wait for a suitable bee. It is known as a triungulin (plural triungula) as it has three claws on each foot. The hooked feet enable a firm hold on an unwitting bee collecting pollen for its own nest. Once in a bee’s nest the larva disembarks and eats the bee’s eggs and the store of pollen and nectar. It then pupates in the burrow until it emerges as an oil beetle, the following spring.
Oil beetles have been identified as priorities for conservation action through the UK Biodiversity Action Plan – meaning urgent work needs to be done to conserve them and their habitats.
Please keep a look out for these beetles when out walking, and submit your sightings to your local biological record centre: