June 2018 - Common Cockchafer (May Bug)


They aren't actually bugs and they don't only fly in May. They are in fact large beetles (apparently the name cockchafer means 'big beetle' in Old English), about 2.5-3cm long, belonging to the scarab family which includes dung beetles. If weather conditions are right, they can be seen flying as early as April as well as during May to July. They don't sting, although there are reports of them biting in defence. Their long pointed, sting-like appendage on the rear of the abdomen is used when the females deposit their eggs into the ground. The adult beetles have whitish triangles on their sides, hairy bodies, reddish-brown wing cases that meet in the middle and orange fan-like antennae used to detect pheromones which help them find mates.

Female cockchafers lay about 20 to 80 eggs in the ground over the period of their life. These hatch into white, C-shaped grubs, each having six legs and a reddish-brown head. They spend the next three to four years as grubs (larvae), gradually growing to about 4cm in length. They are ideal food for a whole range of birds and mammals and are sometimes called rookworms, reportedly being a favourite food of rooks. If your lawn suffers from patches of yellowing dying grass, it may be a sign that cockchafers are in residence, feeding on the roots of the grass, gradually killing whole areas. A hole in the lawn, made overnight, maybe a sign that an animal is digging down to find this nutritious grub. Depending on the numbers involved, cockchafer grubs can cause considerable damage to pastures and crops, as they eat their way through a variety of plant roots. They pupate in the soil prior to becoming adult flying insects.

Unlike the grubs, the adults which emerge in the spring, only live for five or six weeks, enough time to find mates and for the females to lay their eggs. The adults are clumsy fliers, flying at dusk on warm evenings, making a loud buzzing noise. They can sometimes be seen flying around the top of trees at dusk. They are particularly attracted to lights and can fly into your windows attracted by the indoor lighting. They can also turn up in moth traps as these use lights to attract night flying moths. They feed on leaves during this stage of their lives and often become food for bats and owls.

They are common insects. Alternative names for this beetle are Billy witch and spang beetle.



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