Species of the Month

Cockchafer beetles are large, with adults growing up to 30mm in length. They have a black body with brown legs and reddish–brown ribbed wing-cases (elytra). Their undersides are covered in fine white hairs, and the head and pronotum (the hard plate-like structure covering the body just behind the head) are blackish and covered in short hairs.  

Cockchafers, along with stag beetles, dung beetles, dor beetles and scarabs, have distinctive, fanned antennae. The last three to seven segments are expanded into flat, plate like ‘leaves’ which are arranged in a fan. As these are chemo-sensors, this increases the surface area for detecting pheromones. The cockchafer male has seven of these ‘leaves’ while the female only has six, so the male can find the female even in the dark! 

The females have a sharp point at the end of their bodies. This is called a pygidium and is used to lay eggs in the soil.  

The larvae are large, fat, yellow-white grubs with light brown heads and a curved body shape. They can grow up to 40 to 46 mm in length and live in the soil.  

The adult eats flowers and leaves while the larvae live in the soil and feed on plant roots and tubers.  

Their life cycle begins as an egg laid in the ground between June and July. This hatches into a larva which feeds on the roots of plants and tubers for about three years (five years in colder places) and grows to about 40–46mm before retreating deeper into the soil to pupate. In spring the adult beetle emerges, which lives for five to seven weeks during which time they mate and lay their eggs to complete the cycle. A female can lay up to 80 eggs. 

• The cockchafer beetle has many other names such as Billy witch, spang beetle, mitchamador and Maybug. It is also known as the doodlebug because of the buzz of its flight, which was the nickname given to Germany’s V-1 flying bomb in World War II. 
• The larval grubs are sometimes called ‘rookworms’ because they are loved by Corvids.  
• Cockchafers were once very abundant, but with agricultural intensification, the larvae were considered to be an agricultural pest, and the adults were caught to break the life cycle. Their numbers also declined significantly due to pesticide use in the 1900’s, however, since the regulation of pesticides their numbers have increased.  
• In some countries the larvae and adults are considered a delicacy and eaten. 

Although it is widespread in the UK, it is less common in the north. They are found in gardens, parks, meadows, field hedgerows, and woodland margins where there are trees, shrubs and grasses in which to feed and lay their eggs.  

There are lots of top tips for helping beetles. Provide habitat for them in your garden by building a beetle bank, dead hedge or beetle bucket to provide shelter and breeding places. Don’t think of them as pests and if you find a larva, don’t kill it, instead bury it in a beetle bucket specially for that purpose or a spot in the garden. You can also help by not using chemicals in the garden.