by Regina Cutter Edwards
As the days get shorter and the temperatures get cooler, what happens to all the beautiful butterflies? This is a common question in the mid to upper portions of the Unites States. The answer can be short and sweet, most are still there. But for the curious mind, that does not answer the important and interesting question of “where?” The key component to understanding the answer to this popular question is to understand the life cycle of the butterfly. There are four stages; egg, larva (caterpillar), pupa (chrysalis), and adult. For more detailed information regarding the life stages, please read the The Mysteries of Life article. For those who are already familiar the life cycle; let us talk about the cold.
Butterflies are cold-blooded, which means they do not regulate their own body temperature, they depend a lot on their environment. A butterfly can fly when temperatures are around 60-100°F, but their body temperature must be at least 85°F. This is the reason butterflies often bask in the sun, to increase their body temperatures. In the fall, when temperatures begin to get cooler, butterflies have to find a safe place to overwinter. It is at this time they seam to disappear. So where do they go?
Many butterflies, such as the Common Buckeye, Painted Lady, Red Admiral, and Cloudless Sulphur migrate each year to warmer locations. The Monarch butterfly completes the most popular and furthest migration of all the butterflies, which can reach up to 2000 miles. These migrations are fascinating and not completely understood, but for more information please refer to the A Rhythm in Nature article.
Diapause is a form of hibernation in the insect world. It occurs when the juvenile hormone, which is triggered by light and/or temperature, decreases in the butterfly. The butterfly enters an inactive state, metabolism slows down and feeding and reproductive behavior ceases. This occurs on a predictable cycle and begins before the unfavorable environmental conditions, such as cold weather. The butterfly will come out of diapause when environmental conditions again become favorable. The Monarch butterfly, although it migrates, stays in a diapause state while in Mexico overwintering.
Butterflies in the adult stage of their life cycle that do not migrate will stay in the same location throughout winter. They will find a small crack or crevice in a rock, tree, or a building to squeeze into for protection from wind and predators. To prevent freezing, insects produce an anti-freeze compound in their bodies that prevents ice from forming in their hemolymph (insect blood). On a sunny day, if their body temperature gets warm enough, it is possible to see a butterfly in the middle of winter. The Mourning Cloak, Question Mark, and Comma are a few of the butterflies that will stick around during the winter months. Overwintering butterflies are usually angle-winged butterflies and are a dark color.
Many butterflies, such as swallowtails and some whites and sulphurs overwinter in the pupa stage. They are usually the species that feed on woody host plants and the chrysalises have a silk harness that is attached in the middle of the chrysalis to the twig. This extra silk thread is for extra support from the winter winds. It is also not uncommon to find a chrysalis underneath leaf litter in the spring, so be careful when cleaning out the flower beds in the spring.
There are some butterflies that are capable of making it through winter while they are in the larval stage. The Viceroy butterfly, for example, will overwinter in a curled up leaf of the host plant. The caterpillar enters diapause and the body functions slow down and the caterpillar ceases to eat until favorable environmental conditions return. The Baltimore Checkerspot is another butterfly that overwinters as a caterpillar; it hibernates at the base of plants in leaf litter.
The Banded Hairstreak is one type of butterfly that overwinters as an egg. The eggs are laid on the leaves of their host plants; Hickory, Walnut, or Oak and will hatch in the spring. The Poling’s Hairstreak is a butterfly that lays eggs singly on twigs and they overwinter. The Karner Blue butterfly is another example of butterfly that overwinters as an egg. There really are not many butterflies that go through winter as an egg but it does occur.
Life Cycle of Butterflies
The life cycle of butterflies is amazing, and butterflies have the ability to successfully survive winter in all stages of their life. The next winter you are walking outside in the cold, think of the lovely butterflies that are hibernating nearby and are waiting for the warm weather. It will give you another wonderful reason to look forward to spring.