Scientists have found that Madagascar hissing cockroaches (Gromphadorhina portentosa) actively change their social behavior in response to changes in air humidity. New research from Binghamton University (USA), published inEthologyshowed: in dry conditions, these large insects often form dense groups, being in physical contact with each other. Such “hugs” help reduce moisture loss and protect cockroaches from dehydration.

Madagascar hissing cockroaches, 5–7.5 cm long, live in large groups in their natural environment in Madagascar. The experiment showed: at low humidity, cockroaches are much likely to gather in dense clusters.

According to scientists, this behavior is a flexible adaptation that allows insects to retain moisture. Due to their large surface area to volume ratio, cockroaches quickly lose water through their cuticles and respiration, and being together creates a localized microclimate with higher humidity. Previously, such strategies were observed in small species of cockroaches and larvae, but the study showed that large adult insects have also developed such behavioral features to protect against dehydration.

However, grouping also has disadvantages: large concentrations of cockroaches can increase competition or attract predators. Changes in this behavior potentially affect the ecosystem, as hissing cockroaches play an important role as decomposers, breaking down organic matter. Against the backdrop of climate change – increasing droughts and falling humidity – their survival strategy may change, affecting nutrition, reproduction and ecological connections.

It remains unknown to what extent the findings apply to other large insect species, but the data suggest that the dependence of behavior on dry air may be common to many groups.