The cockchafer

David Chapman / 07 May 2019

Wildlife expert David Chapman introduces the cockchafer, a large and often misunderstood insect.



A settled spell of sunny, dry weather has encouraged us to spend a day in the garden, tinkering with a few weeds whilst enjoying the last of the cowslips and the first of the buttercups in the wildflower meadow at the bottom of our lawn.

It’s warm enough to eat lunch outdoors on the wooden furniture that serves more often as a garden feature than a picnic bench but it’s always glorious when it is able to fulfil its purpose. As dusk draws in we retire to the conservatory for evening meal where we can remain in touch with the garden but keep warm as the sun sinks behind the hill to our west.

Soon it becomes quite dark so we turn on the lights inside our conservatory. The lighting creates a lovely glow which surrounds and embraces us in its warmth but at the same time immediately isolates us from the darkness outside.

Suddenly our peace is shattered by a smack against the glass outside. After the initial surprise our heart rates soon return to normal because we know exactly what caused the sound; it was a cockchafer. The first smack was quickly followed by a second and a third as several cockchafers become attracted to our lights but find a pane of glass in their way.

The cockchafer is also known as the maybug because it has a strong association with this month, a time of year which has always been rich in wildlife and welcomed by people. By my reckoning it is the most popular month for lending its name to creatures in the natural world. We have the maybird, or whimbrel, a wading bird which migrates through the UK during spring and autumn, most commonly seen in May. There is the mayflower, aka the cuckoo flower, which peaks when the cuckoo returns from late April, through May. May blossom, the flowers of the hawthorn, can be seen in our hedgerows through May; some species of mayfly emerge from the water for a single day each May and mayweed is a common flower of arable fields.

Of all these species the maybug, or cockchafer, is the most obvious because it’s the only one that knocks on the windows of our houses!

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The naming of cockchafers

‘Cockchafer’ literally means ‘big beetle’ in Old English. An adult cockchafer can be over an inch long. Some people are alarmed by the shape of the pointed segment at its rear but the cockchafer cannot sting; it is harmless to us.

Identifying cockchafers

On the ground a cockchafer bumbles around inelegantly carrying its over-sized, chunky body. Most of its body mass is covered by terracotta-coloured wing cases and when these are lifted the cockchafer is ready for take-off. I would love to say that the bumbling cockchafer is transformed by flight into a creature of great elegance but its flight is more about purpose than grace. Females emit a pheromone which attracts the males and the two fly around at dusk, with a clattering and humming of wings, trying to find each other before they knock themselves senseless on a nearby window.

Both male and female have elaborately-fanned, orange antennae. Within these antennae the males have seven leaves compared to the female’s six. It isn’t uncommon amongst insects for the males to have better developed antennae because they need them to detect the scent of the females.

Once mated female cockchafers use their pointed rear segment to probe into the ground and lay eggs. From these eggs will hatch a white grub which has a brown head. Over the next three or four years these grubs gradually grow, feeding on the roots and tubers of various plants, until they are about the size of a little finger and ready to pupate.

The cockchafer was once a very common insect but the fact that its larvae eats roots made it unpopular in arable farming areas. Through the 20th century its numbers declined as it was targeted by pesticides but restrictions on some types of chemical have seen a slight recovery in their numbers since the 1980’s according to the conservation charity, Buglife.

Their adult form is relatively short-lived with cockchafers living between late April and late May but this is an important part of the beetle’s life cycle because it allows males and female to mate with each other and disperse to find new areas to inhabit.

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