Overwintering of water boatmen (Hemiptera: Corixidae)

We investigated the ability of water boatmen (Hemiptera: Corixidae), an aquatic insect, to survive the winter encased in air pockets within the ice of shallow wetlands. We extracted and experimentally thawed large blocks of ice from prairie wetlands in Saskatchewan, Canada, from which we examined the species composition and revival of corixids. While multiple corixid species were present in wetlands prior to freeze-up, two species, Cymatia americana Hussey, 1920 and Dasycorixa hybrida Hungerford, 1926, comprised the vast majority of corixids that were found in the ice later in winter, and only C. americana revived after ice thawing. Being encased within an air pocket appears to be necessary for the survival of corixids in the ice. Other invertebrate taxa also revived after thawing, including Haliplidae and Dytiscidae encased within air pockets both alongside corixids and on their own, as well as Coenagrionidae, Phryganeidae, Leptoceridae, Chironomidae, Physidae, and Planorbidae, which appeared to be encased in solid ice. The ability to overwinter inside ice represents a little understood survival mechanism of aquatic invertebrates in shallow wetlands.