While ubiquitous during the spring and summer, you don’t really see wasps in winter. Why is that? Do they migrate like birds? Do they hibernate? Do they die? While wasps aren’t migratory, what happens to them in the winter depends on the type and sex of the wasp. There are more than 100,000 species of wasps divided into two broad categories: social and solitary. Check out some of our other wasp articles to learn about common types of wasps and their life histories. No matter the type, however, the wasp lifespan is usually about 3 to 6 weeks or the length of a season. Wasp season tends to run from spring through summer. Some wasps hibernate during the winter or go into an arrested larval stage, while others die at summer’s end. Even during wasp season, they’re less active at night. Temperatures below about 50oF (10oC) make it difficult for wasps to fly. The best wasp habitat is a warm one.
Social wasps build colonial nests that remain active throughout the spring and summer and are usually not re-used the following spring. If winters are mild, however, nests can remain in use for more than a year. As summer ends, fertile adult wasps mate. Male wasps die after mating while fertilized female wasps seek out shelter to hibernate. They typically shelter beneath the bark of trees, within crevices in buildings, or they burrow underground. They may even make their way into your home to hibernate in a dark, safe place. If your home is warm enough in the winter, it may trigger a female to come out of hibernation too early. When this happens, you’re likely to find dead or dying wasps in your house in the winter. When the weather cools down and food becomes scarce, the remaining members of the colony die. Only fertilized females survive through the winter. During hibernation, wasps tuck their antennae close to their bodies and hold on to their shelter with their mouths. Many die during the winter, often as prey to other insects or spiders. The following spring, warm weather signals the survivors to come out of hibernation. They will emerge, find a good nesting site, and begin a new colony as queens.
Solitary wasps do not live communally. Rather, each female nests alone. In species that lay their eggs within nests (mud daubers and cicada killers), most overwinter as larvae within their nest cells and emerge in the spring. The larvae enter a state called diapause, during which all development (including growth) stops. Larval wasps can be kept in diapause for years and still develop into a normal adult when development restarts. Diapause is a good way to overwinter because it prevents starvation during periods of low food availability and ensures that the new population emerges at roughly the same time in the same stage of development. This increases the chances of successful reproduction. Diapause is likely triggered by a combination of changes in temperature and the light/dark cycle as winter begins. When rising temperatures trigger the end of diapause, larvae spin cocoons, complete development, and finally emerge as adult wasps. Some adults of one species of mud dauber, the organ pipe mud dauber, may hibernate during the winter and come out to mate in the spring.
Parasitic wasps, on the other hand, overwinter within or atop their host. Fertilized female parasitic wasps lay their eggs on or in the bodies or eggs of other insects or spiders. When the eggs hatch, the larvae feed off the host. Some larvae spin cocoons at the beginning of the winter and overwinter within the cocoon, while others overwinter like mud daubers and cicada killers and spin their cocoons in the spring. Given the wasp lifespan and food scarcity in winter, it is likely that adult parasitic wasps perish as winter sets in.
There are only a few options for a wasp in winter: hibernate, go into diapause, or die. Despite the diversity of wasps, within each broad category, wasps have similar winter activity patterns. In social wasps, mated females survive the winter in hibernation while unfertilized females and males die when the temperature drops. In solitary wasps, larvae overwinter in diapause either in a nest or a host while the adults die, their reproductive quest complete. Whatever happens to them, it is highly unlikely to spot a wasp in the winter. While this is welcome news to many people, it bears keeping in mind that wasps are very beneficial to natural and garden ecosystems and their emergence in the spring should also be welcomed.