How insects survive during the winter months depends on several things.<\/p>\n
Some of their survival depends on whether they are of a species that spend the winter above ground as eggs laid on plant material or sheltered in leaves or mulch. Butterflies, lady bugs, and aphids are good examples of these. If the winter is not particularly brutal and the temperatures haven\u2019t been cold enough for a broad kill, the aphid infestation is generally bad the following summer.<\/p>\n
If the insect typically overwinters in the ground, some protection is offered initially, but if the conditions aren\u2019t harsh and the soil doesn\u2019t freeze deeply, infestations can be bad the following year too. Good examples of critters that spend their winters underground are hornworms, some grasshoppers, and grubs.<\/p>\n
The bad news is that through the years insects have adapted to their environment and the likelihood of their survival largely depends on whether they have a freeze-avoidant or freeze-tolerant mechanism.<\/p>\n
Freeze-avoidant is the most common adaptation. The insects that have developed this system can tolerate cold temperatures and freezing to a certain point, but will die off when temperatures drop below the freezing point of their bodily fluids. For many, it will take temperatures in the 0 to -20 range before this starts to happen. Emerald Ash Borers, for instance, can tolerate temperatures up to minus 30 degrees which is why they\u2019ve been so difficult to manage on the Front Range- populations simply don\u2019t die back very effectively. Many common insects in our area that overwinter here are freeze-avoidant which is how those populations continue to persist. Good examples include aphids, many borers, and pine beetles.<\/p>\n
Freeze-tolerant insects are the kings and queens of adaptation and can survive temperatures low enough to cause as much as 65% of their bodily fluids to turn to ice. It\u2019s almost impossible to kill these pests off, and even during the harshest winter, they will survive. Most common examples of insects that fall into this category are cockroaches and woolly bear caterpillars.<\/p>\n
If that wasn\u2019t complicated enough, a few other factors can influence how well insect populations survive the winter too. One is the amount of moisture that is to be found in the soil and in the general area where the bug is overwintering. If it is too dry, that will be effective in drying out their habitat and can cause die off in some species.<\/p>\n
Late spring temperatures can play a role as well. A late freeze in May or June can be very effective in killing back the populations that have already begun to emerge and reproduce.<\/p>\n
No matter how harsh the winter, insects have become the masters of adaptation and can not only survive, but sometimes thrive, during the following summer. While I applaud the survival skills of friendly bugs like lady bugs, each summer evening when I\u2019m sitting outdoors, I wish the mosquitoes had been a little less adaptive!<\/p>\n