Cockchafer

May beetles are among the prettiest beetles. But just a few decades ago, the creepy-crawlies were feared as pests in the forest and on the fields.

Characteristics

What do cockchafers look like?

Cockchafers are insects and belong to the Scarab beetle family. This is one of the largest insect families of all: They include about 20,000 different species of beetles, including the largest in the world such as the Goliath and Hercules beetles.

They are called scarab beetles because the ends of their antennae are made up of small leaflets that are split like a fan. Cockchafers grow two to three centimeters long. Like all insects, they have six legs. The brown wings, the black pronotum, and the black and white zigzag pattern on the side are typical of cockchafers.

Some cockchafers are hairy. Under the two thick, rigid elytra are two thin skin wings protected. The feelers of the may beetle are particularly striking. Males and females can be easily distinguished from one another by these: Male cockchafers have antennae with seven leaves each, and females only have six leaves, which are also significantly smaller.

 

The feelers are for the beetles what the nose is for us: the so-called olfactory sensors are on them. And because the males have larger antennae, they also have more of them than the females: males have up to 50,000, while females only have about 8,000.

Where do cockchafers live?

Cockchafers live throughout central and northern Europe and in the temperate zones of Asia. Cockchafers are mainly found in deciduous forests because the leaves of the trees are their food source.

Which may beetle species are there?

We have around 220 different scarab beetles living here. In addition to the well-known may beetle, which is also called the field cockchafer (Melolontha melolontha), there are two other closely related species: the 2.2 to 2.6-centimeter large cockchafer (Melolontha hippocastani), which lives more in the north and east, and the very rarely occurring Melolontha pectoralis, which is at home in south-west Germany.

The three cockchafer species can be distinguished from each other primarily by the last segment of their abdomen, which is triangular in shape and narrower and longer in the field cockchafer than in the other two species.

How old do cockchafers get?

The development cycle of the cockchafer lasts three to four or even five years, depending on whether they live in a warmer or cooler region. But the life of the adult beetle is short, about four to seven weeks. After mating, the males die; the females die after laying their eggs.

Behavior

How do cockchafers live?

As the name suggests, the May beetle’s main flight time is May.

Cockchafers used to be feared because they appeared in large numbers in some years. And because the beetles and grubs – as the larvae of the May beetle are called – have a huge appetite, they could cause great damage to the forests and agriculture. Larvae can destroy entire vegetable fields and grain fields because they nibble off all plant roots.

Adult beetles can even bare entire trees. There used to be real “may beetle years”: In 1911, around 22 million beetles were collected and killed in a forest in the Rhine Palatinate – there was no other way to fight these huge numbers of beetles.

Because cockchafers take three to five years to develop from an egg into a mature beetle, cockchafers are more common every three to four years. And about every 30 to 45 years, mass propagation can occur. The researchers have not yet been able to find out why this is so.

Since modern agriculture has used poisons against insects and modern plows have brought grubs to the surface and die there, cockchafers are rarely found in large numbers. In 1997, 20 to 80 beetles per square meter were only counted again in small areas such as the Upper Rhine Plain and in Thuringia.

Cockchafers have an interesting flight technique: First, they press air into the body through the breathing openings on the side of the body; they really pump up. Then they take off. In-flight, the hard elytra serve as wings, the thin skin wings act like propellers.

But the big bugs are not particularly fast: They can only reach eight kilometers per hour, other insects manage over 50! May beetles flap their wings only 45 to 50 times per second, while other insects such as mosquitoes beat up to 310 times.

May beetle friends and foes

Cockchafers and their larvae are primarily eaten by birds such as crows and seagulls, as well as bats. Moles, hedgehogs, shrews, and wild boars are particularly dangerous to the grubs.

Between 1950 and 1970, people fought intensively against cockchafers and almost wiped them out: helicopters sprayed insecticides where cockchafers appeared to prevent them from multiplying in large numbers.

How do cockchafers reproduce?

Males die shortly after mating. The females still have nine to 21 days to eat. Only after this so-called maturation feeding is the eggs ready to be laid.

The female digs a 10 to 40 cm deep hole in the ground near a tree with her front legs and lays 10 to 30 oval white eggs in it. She repeats this once or twice more. After four to six weeks, the larvae, which all scarab beetles call grubs, hatch. They are white to yellowish in color and have a hard head capsule.

They live underground for three or four years and feed on plant roots. During this time they grow and molt several times until they are about two inches tall. In the summer of the last year of development, they finally pupate and the May beetles hatch from the pupae in autumn.

For the time being, however, they remain in the ground, hibernate there and only crawl to the surface of the earth next spring. They usually come out of the ground towards evening and fly toward dark silhouettes on the horizon. They automatically land on the nearest deciduous trees.

Care

What do cockchafers eat?

Cockchafers are pure herbivores. They mainly feed on leaves from deciduous trees such as oak, beech, willow, hazelnut, maple, and fruit trees. From time to time they do not stop at conifers such as the larches with their soft needles. If cockchafers occur in large numbers, it is quite possible that they eat entire trees bare. The grubs feed on plant roots.