Dragonflies are found almost everywhere in the world in a variety of colors, sizes and shapes. Depending on the region, the predatory insects differ in their appearance in a characteristic way: While dragonfly species in northern regions are generally darker in color, as can be seen in the photo, species in sunnier countries tend to be lighter.
A team led by Roberto Novella Fernandez and Christian Hof from the Julius Maximilian University of Würzburg (JMU) have found in a new study that the coloration of dragonfly communities is not only geographically determined, but also varies over the course of a year. The researchers discovered this when they evaluated observation data from dragonfly communities from 1990 to 2020 in Great Britain.
“For the first time, we were able to demonstrate that the average body brightness of dragonflies not only differs between warmer and colder areas, but also that brighter species are more likely to be found during the course of the year in months with stronger sunlight, i.e. in summer, and in spring and autumn darker specimens fly,” explains Novella Fernandez. The biologists suspect that this helps the cold-blooded insects with their thermoregulation: bright colors reflect the sun and thus prevent them from heating up too much. Darker colors, on the other hand, absorb more solar radiation and warm the dragonflies in the cooler seasons.
In addition, the evaluated data shows that this seasonal color variation has changed as a result of climate change. Novella suspects a shift in the pattern in a direction that is rather unfavorable for the dragonflies. The aim of future studies is to investigate this development in more detail.