Oil Beetle

Meloe spp.

Oil Beetle

profile icon2016-Meloe-Moscow
by ivtorov (CC0)
1 of 4
A close up photograph of an oil beetle to scale from genus Meloe
profile icon2016-Meloe-Moscow
by ivtorov (CC0)
1 of 4
Meloe is a genus of beetles in the Blister Beetle family (Meloidae). Commonly referred to as Oil Beetles, these insects are able to secrete oily droplets from between the joints of the leg. This contains the toxin cantharidin, a potent chemical that can cause extreme burning and irritation, so please don't touch! A characteristic of this beetle group is that they've lost the ability to fly like other beetles, so the wing cases are reduced, revealing the segmented abdomen segments. The larvae parasitise bees nests. Larvae sit and wait on flower heads until a bee lands; they then hop on and get a ride back to the nest. Here they deplete nest stores, sometimes predating bee larvae too!
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Traits

It's thought that declining bee populations will have an indirect impact on Oil Beetle numbers.
Although these beetles are parasites as larvae, they still perform an important role in the surrounding ecosystem.

Appearance

Oil Beetles are typically matt-black. They've lost the ability to fly, so the elytra (protective wing casings) are dramatically reduced. They're so short you can see the abdominal segments beneath. They're sometimes described as an overweight man in a waistcoat because the abdomen is almost swollen and the wingcases barely cover it. The adults are rarely seen unless walking on bare ground. Typically, they like to be concealed beneath open vegetation, but can sometimes be seen on flowers. The larvae are quite unusual looking. They are small and segmented. They have to be reasonably discrete because they need to attach to the body of a bee while being undetected. They sit and wait on flower heads.

Activity

Diurnal

Personality

Order

Coleoptera

Family

Meloidae

Metamorphosis

Complete

Distribution

Closely associated with habitats comprising solitary bees.

Biological treatment

When hand-picking, it's essential to wear gloves because these beetles secrete a potent blistering agent. It can cause extreme irritation when in contact with the skin, so be safe when spot picking these beetles! These beetles rarely do any damage in gardens.

Chemical treatment

None available

Attracts this pest

The adults feed on wildflowers and grasses while the larvae feed within the nests of solitary bees.
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Knowledge and advice

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