The cockchafer and the cockchafer larva (grubs)
Cockchafer beetles, with their maroon elytra, orange antennae and white triangles, under the elytra, are beautifully colored beetles to see. A pointed buttocks and chestnut brown to red legs with feet make the May bug very recognizable. The beetle lives in the ground as a grub for three to four years and feeds on the roots of grasses and plants that slowly die. The grubs cause so much damage to private gardens, football fields and golf courses. The adult cockchafer feeds on the leaves of trees such as oak, beech, walnut and fruit tree, which can lead to trees without leaves in the summer.
- The cockchafer (Melolontha melolontha)
- Characteristics of the cockchafer
- The head
- The antennas
- The mouth of a cockchafer
- The chest piece (thorax)
- The abdomen (abdomen)
- The legs
- The mating
- A complete metamorphosis
- Cockchafer explosion
- Other leaf beetles (Scarabaeidae) and grubs
The cockchafer (Melolontha melolontha)
The cockchafer or common cockchafer is a winged insect from the order of the beetles (Coleoptera), the family of the scarab beetles (Scarabaeidae) and the genus Melolontha. The cockchafer has many small whitish hairs which make it look like there is flour on the body and in the Netherlands the cockchafer is also called mulder, derived from miller.
Characteristics of the cockchafer
The cockchafer is a three-inch-sized beetle with a maroon back and six maroon to orange legs. The cockchafer has chitin armor that provides support and protection against dryness and damage. The May beetles cannot see well but use their antennae. The cockchafer has a body that can be figuratively divided into three parts, namely in:
- the head;
- the chest piece (thorax);
- the abdomen (abdomen).
The head is protected at the top by a bony head shield or vertex. Left and right of the head shield are the black, bead-like and compound facet eyes. A facet eye consists of many identical light detectors (ommatidia) that are close together. The cockchafer is therefore good at registering movement.
The antennae or feelers have an orange color and end in a thickening. This thickening consists of different parts (lamellae) that contain many sensory cells to perceive smells. When the blades fan out, they are used to find food. In the male they are also used to find a female. The male has seven orange lamellae and the female has six. The lamellae in the male are longer than in the female. The May beetles can collapse the antennae to protect them when not needed.
The mouth of a cockchafer
The beak of the adult cockchafer consists of:
- two powerful upper jaws that cut the leaves;
- two serrated lower jaws and a small feeler;
- the lower lip with two small antennae with the taste organs underneath.
The chest piece (thorax)
Behind the head is the thorax or chest piece. The thorax is covered at the top by a dark, hairy and bony neck shield (pronotum). Behind it the two hard and chestnut-colored elytra with a black shield (scotellum) in the middle. The two elytra have fine white hairs and eight (four on each elytra) striking longitudinal ridges. The elytra are the two wings of a total of four wings that the cockchafer has. In rest the elytra are one whole, but when the May bug is about to fly at dusk, the front wings unfold and the other two transparent and veined wings become visible.
The abdomen (abdomen)
The thorax merges into the abdomen halfway between the maroon elytra. The pointed end of the abdomen protrudes under the elytra and is called the abdomen point or pygidium. This rear point is longer in males than in females. The underside and side of the cockchafer is black and white with white, triangular spots on the side, just below the elytra.
The six hairy maroon to red legs consist of different parts (articulations). Each leg is attached to the lower body with the hip (Coxa) followed by the thigh (femur). The next part is the shin (tibia), which has three tooth-like protrusions in the female and two in the male. Also, the shin of the female is wider than the shin of the male. The protrusions on the female are also the digging legs to dig the eggs into the ground. The last part is the foot (tarsus) and consists of five segments, the last segment being the claws, with which the cockchafer holds on to the ground. The cockchafer ?? walks ?? on the shins and feet drag behind it.
In the spring when the adult cockchafer emerges from the ground, the beetle first feasts on the leaves of trees for a while. These leaves, for example from an oak, hornbeam, walnut or plum tree, contain leaf alcohol, an oily liquid. The male cockchafer smells from a great distance the strong and fruity odor of the alcohols released by the damaged leaves and flies towards it. Once near the tree, the male smells the attractants (pheromones) from the female and mating takes place. Cockchafer males mate with the hindquarters points against each other and this can cause strange scenes. The seven lamellae in the photo show that the male is lying on its back and is carried away a bit by the female.
A complete metamorphosis
After mating in May or June, the male cockchafer dies. The female digs into the ground and lays 15 or more eggs divided into groups of four or five eggs at a depth of 10 to 25 centimeters. The females die shortly after laying eggs. After about four to six weeks, the eggs hatch and the larvae that appear are called grubs. The grubs have a distinct ‘C’ shape, a fleshy body and a creamy-white color with orange / brown colored dots on the side of the body, the breathing openings. They also have a hardened orange-brown head with darker jaws and six articulated orange-brown legs. The abdomen of the gerling is colored black / blue and thicker. This is because a grubs do not have an excretory organ and the excrements end up in the back of the body. The grubs grows quickly and sheds three times in an average of three years until it reaches five to six centimeters in size. How fast the grubs grow is partly dependent on the temperature of the soil and the food supply, such as the amount of roots of grasses and plants in the soil. In Northern Europe, where it is colder on average, the grubs live longer in the ground (five years). When the maximum size is reached at the end of the summer, the grubs make a hole one meter in the ground and the last molt takes place in the so-called doll’s room (the doll’s cradle). After five to six weeks, the young cockchafer hatches in autumn and continues to hibernate. Only in the following spring, at a temperature of about 10 to 11 degrees, the young adult cockchafer emerges from the ground. The egg, larva, pupa and beetle have undergone complete metamorphosis and the young adult cockchafer is sexually mature within two weeks.
Because the grubs have a development cycle of usually three years (in the Netherlands), a Mayfly explosion can occur one year and not the next year. Where the many larvae of the cockchafer feed themselves underground in the summer on the roots of plants and grasses, a lot of dry, brown and dead grass is formed, which is typical of a cockchafer explosion. The cockchafer lays the eggs in sandy soils and can cause a lot of damage, especially in the middle and east of the Netherlands. Grasses are also damaged by the animals that eat grubs. Animals such as the mole, hedgehog, badger, boar and lots of birds.
Other leaf beetles (Scarabaeidae) and grubs
Leaf beetles where, just like the cockchafer, the larvae are called grubs and cause damage to the lawn, plants and grasses, are the:
- cockchafer (Amphimallon solstitialis). The grubs live in the ground for an average of two years;
- July beetle (Polyphylla fullo). The grubs live in the ground for an average of three years;
- rose beetle (Phyllopertha horticola). The grubs live in the ground for a year;
- The rhinoceros beetle (Oryctes nasicornis). The grubs live for three to five years in a compost pile, in rotting plants or in wood chips and do not damage the garden.