Ideal conditions for millipedes The crawlers are conquering our homes

The cold, wet weather in the first half of the year has led to a mass occurrence of millipedes. At the same time, wasps are much rarer this year.

The damp weather in the first half of the year provided ideal conditions for greenhouse millipedes, also known as Oxidus gracilis. These animals prefer wet environments, which was abundant this spring.

Marcus Schmidt from the City of Zurich's Pest Prevention Department told the Tages-Anzeiger newspaper about a significant increase in inquiries about these animals.

The striking thing about Oxidus gracilis is that they rarely appear alone. Thousands of these creepy-crawlies move across floors and facades, entering houses through windows and cracks. Why they do this is not fully understood. "There is no food for them in the houses, and they dry up and die quickly," explains Schmidt.

Millipedes cause no damage

These arthropods are harmless to humans. They cause no damage and pose no danger. At most, they can secrete an unpleasant-smelling secretion if they feel threatened. "The millipedes are therefore at most a nuisance," says the expert.

The greenhouse millipede originally comes from Asia and was brought to Europe via imported garden soil. Initially, their occurrence was limited to greenhouses and botanical gardens, but they are now also widespread in the wild. They were first reported in Zurich in 2006 and their numbers have increased significantly since 2020.

These millipedes feed mainly on dead plant material. Scientific information on this introduced species is limited, especially on whether it threatens native species.

Fewer wasps this year

To prevent the crawling creatures from entering, windows can be fitted with insect screens or barrier tape can be attached to façades, as millipedes cannot overcome smooth surfaces despite - or because of - their thousand feet. Double-sided adhesive tape also provides an effective barrier, but needs to be replaced regularly.

While millipedes have increased this year, the number of wasps has decreased significantly due to the damp weather. "Many wasp colonies have developed poorly or died because of the wet conditions," says Schmidt.

Normally, five to ten wasp nests are reported per day at this time of year, but this year there have only been two to three reports so far.

However, Schmidt is not yet giving the all-clear: "It is possible that some wasp populations will grow later in the year. It won't be possible to definitively assess the impact of the cold and wet weather on the wasp population in Zurich for another month."