Adult oil beetles live for a few months and feed on the leaves and petals of spring flowering plants such as lesser celandine, and grasses. The female beetles are considerably larger than males and become much larger when their abdomens become swollen with eggs.
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| Amorous Black oil beetles start about creating a new generation |
The adult beetles search for a mate and a suitable place to dig a nest burrow.
The female beetle must lay lots of eggs to ensure that enough larvae make it through their complex life cycle. They can lay up to 1000 eggs, usually in 2-3 burrows dug into the soil near to where there are bees digging their own nest burrows.
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| Oil beetle eggs |
Leggy larvae
The eggs hatch into leggy, louse-like larvae known as triungulins. These larvae are very active, and for good reason – in order to survive and reach maturity they must immediately find a bee and hitch a ride on its back.
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| Can you find the oil beetle larvae hitching a ride on this bee? |
To have the best chance of meeting a bee, the larvae climb up flower stems and lay in wait within a flower. A solitary bee collecting pollen for its own nest may unwittingly become covered in the oil beetle larvae, secured by their specially-adapted hooked feet.
In the nest
Once inside the bee’s nest, the triungulin change into an entirely different larval form and begin to feed on the bee’s eggs and the store of pollen and nectar. The larvae grow rapidly on this nutrient-rich source of food and after undergoing three more moults they pupate and overwinter in the bee's burrow before emerging the following year as adult oil beetles.
