Summer raids of Arocatus melanocephalus (Heteroptera: Lygaeidae) in houses of Modena city (Italy): is climate change to blame?

Arocatus melanocephalus is a small lygaeid performing its life cycle on elms (Ulmus spp., Ulmaceae). Its presence has been recorded in many continental European regions. Its occurrence has been ascertained in Northern Italy since the last century; however it never elicited special attention until summer 2000, when it suddenly started to become a problem for the citizens of Modena (Emilia Romagna). Since that time, every summer on several occasions, thousands of adults of A. melanocephalus leave the trees to enter the houses, gathering in hundreds all over doors, windows, balconies, and penetrating inside the rooms, causing trouble and anger in the people. Among all the possible reasons for this phenomenon, we suggest that climatic changes observed in Modena during the last 4 years may have affected the behaviour and/or the population dynamics of this bug. In agreement with global warming signals, meteorological recordings for this city show a temperature increase of about + 0.8°C/100 year, and anomalous peaks were observed especially during spring months, likely in coincidence with crucial events in the life cycle of the insect. Studies on the reactions of different stages of A. melanocephalus to cold/hot temperatures are currently performed to provide further support to our hypothesis.