Mass aggregations of Idia moths (Lepidoptera: Erebidae) inside hollow trees in Florida

Abstract

Large aggregations reaching over 400 individuals of adult Idia moths were observed and photographed inside two hollow trees in different localities in north central Florida between 2010 and 2018. A species of litter moth similar to Glossy Black Idia, Idia lubricalis (Erebidae), formed what appeared to be monospecific diurnal roosts consisting of both males and females. While this moth’s caterpillars are known to be detritivores, no signs of immature stages or byproducts of larval feeding were found. The uniform orientation of the moths away from the entrance, fluctuation in their numbers, the higher concentration of the moths near the entrance, and the fact that aggregations were found throughout the summer regardless of the weather, suggest that they are formed on the daily basis perhaps using sex pheromones as cues. No mating was observed despite repeated observations at different times of the day, ranging from dawn to dusk. Hence, the exact function(s) of the observed behavior that is akin to the diurnal roosting of bats is yet to be determined.