They crawl on the ground, gathering into a bizarre formation, moving towards an unknown destination that scientists have only been able to speculate about so far.
The larvae of certain species of insects are believed to migrate by forming a large group with numbers in the tens of thousands, crawling on the ground as a mass. This strange phenomenon is referred to as “Pleń” in Poland and “Heerwurm” in Germany.
Since the 17th century, the larvae of Sciaria militaria, a species of dark-winged insect found in Central Europe, have been observed moving on the ground like a gigantic crawling creature, measuring between 50 cm to 10 m in length.
This migration involves thousands to tens of thousands of small larvae.
The phenomenon was first recorded by a Polish individual and is called Pleń. This migration consists of thousands to tens of thousands of small larvae. They crawl on the ground, gathering into a bizarre formation, moving towards an unknown destination that scientists have only been able to speculate about so far.
The earliest mentions of Pleń in Polish documents date back to the 17th century in Silesia. At that time, this phenomenon was associated with misfortune or with prosperity and happiness. Those who believed it to be a sign of prosperity and happiness would collect the larvae, dry them, and then scatter them on their fields and in their barns, hoping for a bountiful harvest.
After World War II, the Pleń phenomenon was observed around 100 times, according to recorded reports in Poland. The most recent occurrence was even captured on camera and observed in the Carpathian Mountains, Biebrza Marshes, and the Białowieża Primeval Forest.
Although the first reports of the Pleń phenomenon may have originated in Poland, it has also been observed in other regions around the world, including forests in Russia, Lithuania, Sweden, Norway, Bavaria, Hungary, Switzerland, and North America.
Based on scientific explanations, the movement of the larvae concentrating into a large “swarm” of thousands or tens of thousands may simply be for the purpose of ensuring a greater speed of movement.
The larvae crawl over one another like a conveyor belt. The larvae on top crawl over those below, and as the others are also moving, this means they are moving twice as fast. However, the larvae on top also eventually move down to the bottom until they find their way back up to the top of the moving mass of larvae.
Overall, if this moving mass is formed of two layers, it will move at a speed one and a half times that of an individual, and if there are more layers, the speed increases further. It’s simply a more efficient way to move.
Regarding the ultimate goal of this migration, scientists hypothesize it may be due to a lack of food or the drying effects of sunlight.
