Bonn/Region · They are about three centimetres in size, their flight sounds easy to hear: May beetles are currently on the move again in some regions. How common are these conspicuous buzzers in Bonn and the region? And are they dangerous?
These days they can be heard and seen again: May beetles are sometimes widespread in North Rhine-Westphalia. The jumbos among the beetles, conspicuous because of their size and flight sounds, show themselves for a few weeks starting in May, hence the name. "The spread and reproduction can vary quite a lot from region to region," the NRW State Office for Nature, Environment and Consumer Protection (Lanuv) informs us on request.
In Bonn, the cockchafer is rather rare. Peter Schmidt of the Bonn/Rhein-Erft Biological Station explains that there are hardly any May beetles found in the Bonn area. Most of them are single reports, there has not been a large occurrence here yet. May beetles are "heat-loving animals", says Schmidt. They tend to occur on warm slopes, in orchards or wild meadows, but also at the edge of forests or in sparse woodland. "May beetles need open ground, open vegetation," the expert explains.
They don't find that in the forests in Bonn either. "We haven't noticed anything yet this year," says Stephan Schütte, head of the forestry office of the Rhine-Sieg-Erft Regional Forestry Office. Instead of sandy and loose soils, there are mainly heavy loamy soils in the Kottenforst, for example, explains Schütte. Not good ground for the cockchafer. In addition, the cold weather of the past months has made the forest soil even more solid and thus even less attractive for the beetles. Even though more cockchafer beetles have been observed in recent years, "basically they are less common in the Kottenforst," says Schütte.
The soil conditions are important for the animals because they live most of their lives underground as larvae. They live underground for between three and five years, says Peter Schmidt. The beetles themselves, which, in keeping with their name, usually dig themselves out of the ground in May, do not live long; they only fly around for about one to two months and reproduce again. These cycles are also noticeable when they appear. "There are always waves like this," says Schmidt. There are always many cockchafer beetles developing at the same time, which then emerge "in waves". In a four-year cycle, for example, three years with low occurrence are followed by a year with significantly more beetles, the so-called May beetle year. "That's why you don't have many insects every year," he says. However, there has never been such a large occurrence in the Bonn area.
Of the three species of cockchafer, the field cockchafer (Melolontha melolontha) is the most common in NRW. The forest cockchafer (Melolontha hippocastani) and the Melolontha pectoralis, which has no German name, are the two rarer representatives of the genus, according to the Lanuv. In general, the field cockchafer is widespread in the lowlands of NRW, but somewhat less so in the low mountain ranges. There is one occurrence in the Münsterland. The last May beetle years always correlate with the years of the Summer Olympics, says Wilhelm Deitermann, press spokesman of the State Office.
Field cockchafer can grow more than three centimetres long, the head, the thorax as well as the abdomen are mostly black, legs, elytra and the fan-like antennae are mostly reddish brown. Despite their size and their clearly audible flight sounds, the insects do not pose a danger to humans, says Peter Schmidt.