• Kirk Mason

An Invader from the Far East?

The harlequin ladybird (Harmonia axyridis) originates from Eastern Asia and is considered one of the most invasive invertebrates in the world!

They were first recorded in Essex, Britain in 2004 after being introduced to Europe as a biological control for aphids. Once these intruders landed in Britain, they are thought to have covered our land at a rate of 105km per year!

Part of the reason for the success of the harlequin ladybird is its ability to tolerate and thrive in a wide range of habitats, living on many host plants such as deciduous trees, herbs and shrubs. Currently this adaptable invader is found in most habitats of mainland Britain but is rarely found in North Scotland due to lower temperatures and high rates of precipitation (rain, snow sleet and hail).

The main reason for the invading harlequin’s success is thought to be mostly due to their lack of natural enemies. They stand as a top aphid predator and have the ability to predate our native ladybirds - making them a force to be reckoned with. They have even been observed eating our native ladybirds when aphids are in abundance!

The wasp injects an egg into the harlequin, which eats it from inside out. After around 20 days the larva leaves the hosts body and spins a cocoon between the harlequins’ legs. A virus develops in the head of the harlequin, causing it to guard the cocoon from predators for approximately one week, until the wasp emerges! Although this behaviour sounds gruesome, these wasps are actually one of the many unsung heroes of the animal world, indirectly protecting our native species!

The wasp is one of few threats to the harlequin, but its list of natural enemies is growing - flies and fungus are also adapting to the presence of this invader from the far east! The evolutionary arms race is constantly moving forward, do you think our native species will catch up and control this incredibly successful invader?

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