Butterflies that remain in New England during the winter spend it in one of many stages – some as eggs, others as larvae or pupae, and a few as adults. Mourning Cloaks, Compton Tortoiseshells, Milbert’s Tortoiseshells, Question Marks, Gray Commas and Eastern Commas all overwinter as adult butterflies. They store fat in their bodies in the fall and replace a portion of the water in their blood with an antifreeze agent, which prevents the lethal formation of ice crystals in their bodies. These butterflies then slip into cracks, behind loose bark, in a hollow tree or some other sheltered spot where they enter a stage referred to as winter diapause. Metabolic and respiratory rates are greatly reduced, and the butterflies remain inactive until the warming, lengthening days of March and April, when they emerge to mate and lay eggs. They often look rather tattered, as they put many miles on their wings the previous summer. Unlike most adult butterflies which live only a few weeks, butterflies that overwinter as adults have a lifespan of eight to ten months. (Photo: Eastern Comma – note white “comma” on under side of hindwing)
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Insects that live in northern New England have different strategies for surviving the winter. Carpenter ants live in the center of both dead and living trees, in galleries that they have chewed throughout their nest. Although wood is a good insulator, it still freezes during the winter. The ants tend to cluster together and enter a state of slowed metabolism called diapause. In addition, carpenter ants also produce glycerol, a compound which acts as antifreeze preventing destructive ice crystals from forming in their bodies.
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The queen is the only wasp in a colony to live through the winter (the others all die), and she usually does so in a sheltered spot such as a rotting log or under the loose bark of a tree (pictured). I wasn’t aware, until discovering this wasp, that queens actually chew a cavity in which to hibernate, but that appears to be the case in some instances. You can see the woody bits of fiber under the wasp that accumulated from her excavating the chamber. The cavity is roughly one inch long and ¼-inch deep. As a rule, hibernating queen wasps protect their wings and antennae by tucking them under their bodies. Some species produce glycerol, which acts as an antifreeze, while others allow ice to form around their cell walls and simply freeze solid. Most queen wasps die over the winter, primarily from predation by other insects and spiders, not the cold. (The pictured wasp had succumbed.) Warm winters are more likely to affect queens, as they emerge from hibernation too soon and starve due to lack of food.