Why the “Salt” Institute?
The University of Minnesota has a long history of insect cold hardiness research that we are continuing. Reginald W. Salt obtained his Ph.D from our department in 1936 and published many seminal papers on insect cold hardiness. He was not the first in the department to study insect cold hardiness, but he did do extensive reviews and was one of the first to outline terminology to describe different aspects of cold hardiness, much of which we still use today.
What does “cold hardiness” mean?
Cold hardiness refers to an organism’s ability to tolerate cold temperatures. In our research with insects, we try to determine the temperatures that kill specific insects (the “lower lethal temperature“). We compare the lower lethal temperature to the point at which the insect freezes (the “supercooling point“) to determine if the insect dies before it freezes (“chill intolerant“), right when it freezes (“freeze intolerant“), or if it can survive freezing (“freeze tolerant“).
Can insects survive being frozen?
Some insects do survive after they freeze! These are called freeze tolerant. In Minnesota, two well-known freeze tolerant insects are the goldenrod gall-fly and the wooly bear caterpillar. Our outreach publication “Tough Buggers” outlines a few of the key ways insects overwinter in Minnesota.
How does wind chill affect an insect’s ability to overwinter?
Wind chill is an estimation based on characteristics of human skin, so how we talk about wind chill (i.e., “the temperature feels like…”) does not apply to insects.