Photo-response of the brown marmorated stink bug, Halyomorpha halys (Stal) (Heteroptera: Pentatomidae), and its role in the hiding behavior

As part of a study aimed at determining the factors affecting overwintering habitat choice by Halyomorpha halys, we examined the behavioral response to light of diapausing adults (which have no reproductive activity) and non-diapausing adults. Bugs were tested individually in a choice chamber (14, 18 and 24 degrees C) containing a dark refuge with opaque (black) sides and roof. Each bug's position in the choice chamber was recorded at regular intervals. The results indicated that diapausing bugs prefer to settle in a dark place (p < 0.05). This preference appeared to weaken at 24 degrees C; however, this apparent trend was probably due to the greater overall activity of the bugs under warmer conditions. In tests of non-diapausing bugs, lower proportions of the bugs were observed inside the dark refuge at higher temperatures; however, the preference for dark places was exhibited under all temperature conditions. Based on these results, we infer that H. halys adults have a fundamental preference for dark places whether or not they are in diapauses, which plays a main role in hiding behavior. This preference becomes most obvious in the winter, with the decrease in behavioral activity resulting from lower temperatures. We propose that this common preference for location is one of the factors responsible for the bugs' convergence on specific microhabitats and the overwintering aggregate formation of H. halys.