Cockchafers, more familiarly known as May bugs, are one of those things that go bang in the night.
They are big brown nocturnal beetles that are easily attracted to light. They fly into your bedroom window with a loud click that sounds as if a burglar just threw a small pebble against the glass to check if you are still awake. If your bedroom window is open, a cockchafer will fly in and noisily batter itself senseless around your bedside lamp.
Their scientific name is Melolontha melolontha; they have black thoraxes, striped abdomens, distinctive light brown wing cases and legs, and very characteristic antennae that fan out. The males have seven branches to their antennal fans and the females have six.
Cockchafers are powerful but clumsy fliers; you can see them at this time of year buzzing around the park in the evening. Because they are large and their flight is noisy, they can be a little bit intimidating, but they are harmless to humans; they don’t bite or sting. However, in their larval stage, they can do considerable damage to agricultural crops and during the latter half of the last century the use of pesticides reduced their numbers drastically.
The larvae are fat, creamy-white grubs with brown heads. They live in the soil, eating plant roots, for about three years, sometimes four or five years in more northerly habitats. They especially like cereal crops and grasses, which makes them a pest in the eyes of farmers. The larvae pupate in early autumn and develop into adult cockchafers in about six weeks. The newly hatched adults enter hibernation straight away and do not emerge from the soil until the following spring.
1. Cockchafer larvae; 2. pupa.
Adult cockchafers begin to appear at the end of April or in May and live for about five to seven weeks. They feed mostly on the leaves, flowers and fruit of deciduous plants, mainly trees and especially oak. At dusk, in May, now that their numbers are recovering, swarms are sometimes seen around the tops of trees and shrubs.
After about two weeks, the females begin to lay eggs, which they bury 10 to 20 cm deep in the soil. After each bout of egg-laying, a female will return to the trees for several days to feed. She will do this three or four times until she has laid a total of between 60 and 80 eggs. The larva hatch after four to six weeks and the cycle is complete.
If you are walking in the park at dusk, listen out for the buzz of cockchafers in flight.
Header picture: Cockchafer (Maybug) by bramblejungle (CC BY-NC 2.0) flickr.com