Diapause and cold tolerance can profoundly affect the distribution and activity of temperate insects. Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), an alien invasive species from Asia, enters a winter dormancy in response to environmental cues. We investigated the nature of this dormancy and its effects on H. halys cold tolerance, as measured by supercooling points, lower lethal temperatures, and overwintering field mortality. Dormancy was induced by rearing individuals in the laboratory or under field conditions. We confirmed H. halys dormancy to be a state of diapause and not quiescence, and the life stage sensitive to diapause-inducing cues is between the second and fifth instar. In the laboratory, supercooling points of diapausing adults reached significantly lower temperatures than nondiapausing adults, but only when given enough time after imaginal ecdysis. Supercooling points of diapausing adults in overwintering microhabitats also decreased over time. Diapause increased adult survival after acute cold exposure in the laboratory and prolonged cold exposure in the field. Following diapause induction in the laboratory, changes to temperature and photoperiod had no significant effect on lower lethal temperatures and changes to photoperiod had no effect on supercooling points. Additionally, induction of diapause in the laboratory did not result in significantly different cold tolerance than natural field induction of diapause. This work demonstrates that H. halys diapause confers greater cold tolerance than a nondiapausing state and likely improves the probability of successful overwintering in some temperate climates. Hence, knowledge of diapause status could be used to refine forecasts of H. halys overwintering field mortality.
Bibliographical noteFunding Information:
We would like to thank Mark Abrahamson (Minnesota Department of Agriculture, St. Paul, MN) for sharing H. halys detection information, the Stoyke family (Wyoming, MN) for allowing us to collect insects on their property, Jaana Iverson and Sarah Holle for colony maintenance, and Amy Morey, three anonymous reviewers, and the subject editor for their valuable reviews of a previous version of the manuscript. We appreciate the permission to use laboratory facilities at the United States Department of Agriculture Forest Service Northern Research Station. We are also grateful to the creators of the R packages that were used for graphing: ggplot2 (Wickham 2009), ggthemes (Arnold 2017), gridExtra (Auguie and Antonov 2016), and Rmisc (Hope 2013). This work was supported in part, by a Minnesota Discovery, Research, and InnoVation Economy (MnDRIVE) Global Food Ventures Graduate Fellowship, an Interdisciplinary Center for the Study of Global Change Global Food Security Graduate Fellowship, and a University of Minnesota Graduate School Doctoral Dissertation Fellowship.
- Brown Marmorated Stink Bug
- Cold Tolerance
- Overwintering Ecology