Ireland’s Beetles: What Is A Cockchafer?
And why do they keep crashing into my kitchen window?
The Cockchafer has many different names – May bug, June bug, billy witch and doodle bug among others (as Gaeilge: cearnamhán nó priompallán samhraidh).
However, it is not actually a true bug. Cockchafers are a member of the Scarab beetle family. In Old English, the name Cockchafer actually means “big beetle”. The nickname May bug refers to the emergence of these beetles in May, although in warmer years they can be seen as early as mid-April. The cockchafer is widespread across Europe in grasslands, hedgerows, oak woods and deciduous woodland margins.
It is one of Ireland’s biggest beetle, reaching up to 35mm in length (larger than the diameter of a €2 coin!). They are large, stocky, brown beetles with large orange fan-like antennae. Males and females can be distinguished by the number of ‘leaves’ on their antennae: males have seven whereas females have six. At the end of the abdomen, they have a sharp ‘tail’, known as a pygidium, which is used by the female to lay eggs in the soil. This is sometimes mistaken for a sting, but these beetles are actually harmless.
You will recognize this species by the unmistakable loud whirring noise that they make while flying. They can fly at a speed of 3 metres per second and although they are powerful fliers, they could also be described as quite clumsy! Similar to moths, they are very attracted to light and are commonly seen crashing into outdoor lights and windows. You might even find them lying on their backs on the ground after flying a little too close to the lights. To help them out, consider turning off your outdoor lights at night during May and June so they can find their way back into the trees.
There are three species of Cockchafer in Europe: the Common Cockchafer (Melolontha melolontha), the Forest Cockchafer (M. hippocastani) and the Large Cockchafer (M. pectoralis). The Large Cockchafer has never been seen in Ireland but the two other species are present.
The Common Cockchafer is, as the name suggests, the most common species and can be seen all over Ireland. The Forest Cockchafer can also be found in Ireland, however there are very few recent records. In the past decade, there have only been six reported sightings of this species – in Kerry, Cork, Waterford, Wexford and Westmeath (Source: National Biodiversity Data Centre). This species is thought to emerge slightly later than the Common Cockchafer although the two species are very similar. However, the Forest Cockchafer is smaller and has a shorter pygidium.
The common Cockchafer has an interesting life cycle. During the adult stage, females lay eggs 10-20cm in soil. Within a month these eggs will hatch into larvae which will remain in the soil for over three years. In this stage they eat plant roots. On their fourth summer they will emerge from the soil as an adult beetle. This emergence usually starts in May and continues through the start of June. In this stage, the beetle only lives for six weeks. During this time, the beetles will eat leaves, breed and then lay eggs in the soil to mark the beginning of a new four year-long cycle.
History with Humans
In the mid-20th century this species faced a dramatic population decline all over Europe due to the introduction of new pesticides. Luckily, most of these dangerous pesticides were banned in the 1980s and cockchafer populations have been slowly recovering. In the past, this species was considered to be an agricultural pest but this has become less of an issue with modern agricultural practices, although the larvae of the Forest Cockchafer are still a pest in commercial forestry in Europe.
There are several recorded instances of cockchafers emerging in huge numbers and causing chaos in local communities. In 1320, this species was involved in a fascinating example of human-wildlife conflict in Avignon, France. Cockchafers were summoned to court and sentenced to withdraw from the area within three days. The penalty for not obeying was death. Unfortunately, nobody told the cockchafers that they were breaking a human court ruling, and of course they did not leave the area. This resulted in a mass collection and killing of cockchafers. Perhaps they were also eaten, as old recipes have been found from France and Germany which describe cockchafer soup and sugar-coated cockchafers.
If you spot a cockchafer this year, please record your sighting with the National Biodiversity Data Centre at http://records.biodiversityireland.ie/index.php
Written by Rebecca O’Sullivan, Zoologist
1 Chinery, M. (1993) Collins Field Guide to The Insects of Britain and Northern Europe. 3rd Edition. London: Collins
2 Huiting HF, Moraal LG, Griepink FC, Ester A (2006) Biology, control and luring of the cockchafer, Melolontha melolontha. Research Report, Applied Plant Research, Wageningen, The Netherland https://edepot.wur.nl/121073