Vyöryvöitä

Vyöryvöitä is a Finnish term that translates to "avalanche moths" or "rolling moths." It refers to a specific type of insect behavior observed in certain moth species, particularly in conditions of high population density. When a large number of larvae hatch simultaneously, they can emerge in massive swarms. These swarms can appear to "roll" or "flow" down vegetation or across the ground, creating a striking visual effect.

This phenomenon is primarily associated with the larvae of hawk moths (family Sphingidae) and some other moth families. The behavior is triggered by a combination of factors, including favorable environmental conditions for breeding, abundant food sources leading to high survival rates, and the aggregation of larvae due to limited dispersal mechanisms. The "rolling" motion is not a coordinated effort but rather a collective movement of individuals seeking food or new areas to feed.

Vyöryvöitä can sometimes cause significant defoliation of trees and plants in the affected areas. While visually dramatic, the ecological impact depends on the species involved and the local ecosystem. In most cases, the larvae will eventually pupate and develop into adult moths, and the population will return to more typical levels in subsequent years. The term itself highlights the visual aspect of these mass larval movements.