You see them flying around and flashing throughout the longest, warmest months of the year; but have you ever wondered, where do fireflies go in the winter? What do they do when the weather turns cold? Keep reading! In this article, we’ll answer these questions and more.
What You'll Learn Today
Where Do Fireflies Go in the Winter?
Most adult fireflies die long before winter arrives. These species may only live for a few weeks to a couple of months, and they generally die after mating and laying eggs in the late summer months.
It is usually the larvae of fireflies that survive through the winter. Firefly eggs hatch out in late summer and fall and spend several weeks eating soft-bodied insects and invertebrates before burrowing underground when the weather turns cold.
Check out this video of a firefly larvae attempting to eat a much larger snail:
Most firefly larvae stay underground throughout the winter months; others take shelter beneath the bark of trees. There, they wait for the weather to warm up again.
Once spring returns, firefly larvae will emerge and begin feeding again. In late spring, they enter the pupal stage, finally emerging as adults in early summer.
This is the common pattern for most fireflies; that said, there are around 2,000 species in the world, and many of them do not follow this pattern perfectly.
For example, the winter dark firefly, which produces no light as an adult, spends one winter in the larval stage and one in the adult stage. This firefly has a much longer lifespan than most, spending about 16 months as larvae and about 8 months as adults.
Winter dark fireflies are so named not only because they lack light producing organs but because they are active earlier than any other firefly species–sometimes as early as late winter. They overwinter under layers of tree bark and emerge as the days begin to grow longer, clustering on the sunny sides of trees and around sap flows.
Again, though, most fireflies spend the winter as larvae. Most species overwinter underground where they can avoid freezing temperatures above the surface.
What Do Fireflies Do in the Winter?
Though their winter homes keep them from freezing, overwintering fireflies and larvae are still subjected to cold temperatures and food shortages. With this in mind, there isn’t a whole lot they can do other than sleep.
Fireflies hibernate throughout the winter. This allows them to store and conserve their energy, helping them stay alive in spite of the harsh conditions they face.
As noted above, firefly larvae emerge from their eggs in late summer or fall. They spend several weeks eating their fill of snails, slugs, worms, and other soft-bodied creatures, growing quickly and building up their own reserves.
When the weather gets cold, they stop eating and burrow underground. Then they sleep until it begins to warm up again.
Shorter, milder winters lead to longer and more abundant feeding periods for firefly larvae; during these years, they may pupate and emerge as adults earlier in the summer. On the other hand, longer and colder winters can lead to a delay in their emergence.
Winter dark fireflies, as discussed above, spend their second winter hibernating as adults. They, too, spend the coldest months sleeping instead of eating; they are most likely to take shelter behind the bark near the base of trees.
Unlike other fireflies, they may start becoming active before the end of winter. They seem to be drawn to sap flows on trees, where they may drink some of the sap to begin replenishing their depleted energy stores.
When Do Fireflies Emerge From Pupation?
Most firefly larvae stop hibernating in early spring, as the days lengthen and the weather warms up. At this time, they begin feeding and growing again.
In late spring, the larvae pupate. They stay in the pupal stage usually for about ten days, though this can vary greatly by species.
Adult fireflies finally begin emerging from the pupas in late spring through early summer. Most adult fireflies make their debut sometime between the third week of May through the third week of June.
Winter dark fireflies follow a different life cycle. They lay their eggs in late spring and early summer, live as larvae for the next 16 months, and emerge from their pupas the following late summer or early fall. They are not really active during the summer months, except as larvae hidden around the bases of trees and feeding on soft-bodied insects.
When is the Best Time to See Fireflies?
The best time to see fireflies is when they are in the adult stage and searching for a mate. This is the time when their iconic light shows are on full display each evening.
Fireflies don’t live very long in the adult stage–usually only for a couple of months. This means that the time period for seeing fireflies is fairly short each year.
You are most likely to see fireflies during the summer months, typically late May through early August. This is when they are typically most active.
That said, if you’re looking for winter dark fireflies, you might want to start looking a little earlier.
Winter darks can be found as early as February in some regions. A good place to look for them is around the bases of trees, on the sunny side of trees during the day, or around sap collection buckets during maple syrup season.
If you know what you’re looking for, you may also be able to find their larvae, which are bioluminescent, glowing in clusters on tree trunks or in rotting wood. This sight is most common during the summer through early fall months.
Most adult fireflies die long before winter arrives; instead, it is their larvae that survive through the winter by burrowing underground and hibernating. They spend the early spring months feeding on soft-bodied invertebrates before pupating and emerging as adult fireflies in the early summer.