Moth slumber parties are held in hollow trees, study says

A researcher just discovered the unique phenomenon of moth slumber parties that contradicts their solitary reputation.

Tyler MacDonald | Oct 09, 2019

Although moths are typically loners, scientist Andrei Sourakov found a unique population of the glassy black Idia speciesinside of a hollow tree. Afterwards, he found 100 of the same species congregated in another hollow tree, and their numbers eventually reached 400.

"That's incredible," he said as he filmed it. "So many moths!"

Each time, the moths oriented themselves at the top of the tree and out of light, keeping slightly away from each other. But they weren't mating and larvae weren't feeding nearby, suggesting that they were resting and waiting for night.

"This is completely new," Sourakov said. "Nobody has recorded daily communal roosting behavior in moths. This appears to be a unique behavior in this species and an important part of its biology."

Although he's not exactly sure why the moths are grouping together,Sourakov believes it might be a "safety in numbers" strategy for defense.

"Large numbers of prey in a confined space presents a challenging environment for predators," he said. "Spiders, for instance, would have to constantly repair their webs torn by these many moths. But most importantly, the percentage of lost prey is not significant enough to undermine the population. 'Safety in numbers' doesn't mean everyone is safe, but the population is safe."

Sourakov believes that the moths signal and plan to assemble using sex hormones.

"There are so many unknowns in nature," he said. "Even the exact identity of this moth species is unclear and is waiting to be described. You don't have to venture into exotic places to make discoveries. Just look in your backyard. Some moths are small, brown and might seem boring, but the impact that stories like this make on a perception of a place cannot be underestimated."

The findings were published in the journalTropical Lepidoptera Research.