Cockchafer

The common cockchafer, known scientifically as Melolontha melolontha, is a species of scarab beetle. It is also called the Maybug, Maybeetle, or doodlebug. These beetles are native to Europe, including Germany, France, and the United Kingdom. They are also found in parts of Asia, such as Turkey and the Caucasus region. The cockchafer is a vital part of the ecosystem because it serves as a nutritious food source for many animals. However, they are also famous for being significant agricultural pests.

This beetle undergoes a complete metamorphosis. This means it changes through four distinct life stages: egg, larva, pupa, and adult. The life cycle is quite long because the larval stage lasts for several years. After the eggs hatch, the larvae, often called white grubs, live underground for three to four years. In colder climates, this period can last up to five years. Eventually, they pupate in early autumn. They then develop into adults over a period of six weeks.

Adult cockchafers have specific physical features that help identify them. They have a black pronotum, which is the area behind the head, covered in short hairs. This black color helps distinguish them from the forest cockchafer, Melolontha hippocastani, which has a brown pronotum. Their bodies have hard, brown elytra, which are the wing covers. The males and females show sexual dimorphism, meaning they look different. Male antennae have seven "leaves" or segments, while females have only six.

Finding a mate involves a complex chemical process. During the mating season in April or May, males often form swarms at dusk. They fly around trees at forest edges to find females. While males swarm, females stay on branches to feed on leaves. When females eat, the leaves release green leaf volatiles (GLVs). These are chemical compounds released by plants under stress. The males use these GLVs as a kairomone, a chemical that helps the receiver find a resource. This scent helps the males locate the females for mating.

Cockchafers can cause serious damage to crops and forests. Adults feed on the leaves of deciduous trees like oak, maple, and beech. They may also eat conifer needles. The larvae, however, are the primary agricultural pests. They feed on the roots of grasses, cereals, and fruit trees. A single larva can gnaw through 30 cm of root in one day. This intense feeding can quickly kill a plant.

Nature has many ways to control cockchafer populations. The European mole is a natural predator that uses a keen sense of smell to find larvae underground. Other predators include ground beetles, ants, and click beetles. Birds such as starlings, crows, and gulls also eat the larvae, especially after fields are plowed. There are even parasites involved. A parasitic fly called Dexia rustica lays eggs that hatch inside the larvae. One to six fly larvae can live inside a single cockchafer host, which eventually kills the beetle.

Humans have interacted with these beetles throughout history in unusual ways. In the Middle Ages, people in Avignon actually brought cockchafers to court and sentenced them to leave. In the 19th century, some people in Germany even ate them. A medical officer named Johann Joseph Schneider reported that they were eaten raw, candied, or in soup. He described the flavor of the soup as being similar to crab. In Sweden, peasants used the color of the grubs to predict the winter weather. They believed a bluish grub meant a mild winter, while a white one meant a severe winter.

Modern technology changed how we manage these insects. In the 20th century, the invention of chemical pesticides allowed farmers to combat them effectively. This led to a massive decrease in numbers, reaching near-extinction in some European areas by the 1970s. However, because of concerns about public health and the environment, many of these chemicals are now being phased out. Scientists are even investigating if green leaf volatiles can be used as a way to attract males and prevent mating as a new type of pest control.