Missing poisonous oak processionary caterpillars may still be dormant underground

The decrease in the number of observed oak processionary caterpillars may be because the insects can spend a year, possibly even longer, underground. A researcher from the Kennisplatform Processierups think-tank observed this week that both males and females emerged from a testing site which they had burrowed into last year. In other places, caterpillars have been observed that, with a short interruption above ground, have even returned underground twice a year. The fact that caterpillars remain in an extended diapause, a form of hibernation, for a year or even longer, may explain why the think-tank caught 40% fewer butterflies in 2019, the year in which the caterpillars were at their peak, than a year earlier.