Mealybug insects as models of a previously undescribed overwintering behavior

Insects, whose body temperature depends on ambient temperature, often take refuge under the soil surface to survive unfavorable winter conditions. Considering the strategies used to cope with cold winter temperatures insects are classified into several groups. Here we propose a new group of insects with a previously unreported overwintering strategy taking as a model the mealybug insect family. Using specifically designed sampling methods we found that these sap-sucking insects, which spend half of the year feeding and reproducing on the plant canopy, move to the rhizosphere during the winter to feed on tree roots and reproduce. Our results show that the preferred area to overwinter for the main female mealybug species is within 1 meter around a fruit tree trunk, where more than 25000 mealybug males per square meter can emerge every spring. This unique adaptive strategy allows these aboveground herbivores to turn into belowground root feeders during the winter.