Article by Tess Renusch, National Wildlife Federation

Published September 30th, 2024

https://blog.nwf.org/2024/09/leave-the-leaves-to-save-fireflies/

Fireflies are in decline, but you can help them by skipping the yard waste bags this year.

If you’ve ever lived in a region with fireflies, you’re probably most familiar with them as flying insects that light up the sky with their rhythmic blinking. But did you know that most of a firefly’s life can be spent under the leaves?

Fireflies as Larva

Like many insects, fireflies go through multiple life stages. The flying bugs we see are their adult form, but before they reach adulthood they first pass through their larval and pupal stages. In fact, for most species of fireflies, the larval stage makes up most of their life! For one species, Photinus pyralis, they spend 1-2 years as a larva, and only 30 days as an adult!

But most people have never even seen a firefly in its larval stage, or if they have, they haven’t realized what they were looking at. Firefly larvae look almost nothing like their adult forms. They often have a long, almost worm-like, body and most do not have any wings or have short wings that they cannot use for flying.

So if they don’t fly, where do these insects live for years on end? The answer lies beneath our feet.

A Life in the Leaves

While each firefly species is different, many fireflies spend their larval stage beneath a layer of fallen leaves or even under the soil. The moist environment that the leaf layer creates is a must for many firefly larvae, since some even depend on gills to breathe! The leaf layer is also helpful for many other insects and small creatures, like snails. Since many firefly larvae are carnivores, these other small animals in the leaf layer are a vital food source!

Not only does the leaf layer provide a moist environment and support a healthy food web for fireflies, but it is also essential for protecting them overwinter. Since many fireflies spend years as larvae, the leaves keep them warm, hidden and protected while they hibernate.

Leave the Leaves for Fireflies

Fireflies are disappearing in America, and how we maintain our yards and gardens is a huge reason why. When homeowners and gardeners fill up yard waste bags with leaves, sticks, and other organic matter, they’re getting rid of the leaf layer that these firefly larvae need.

Not only that, but oftentimes the firefly larvae themselves get put into those yard waste bags and get carted away! About 30% of these yard waste bags end up going straight to the landfill. Some get composted, but others are incinerated– which releases carbon dioxide greenhouse gasses. Wherever these yard waste bags end up, it’s not good news for the fireflies.

To help save the fireflies, you can avoid the yard-waste bags. Instead, opt to intentionally use the fallen leaves in your yard. You can rake the leaves off your paths and lawn and move them to create a beneficial leaf layer in your garden beds and around the base of trees. Leaving the leaves doesn’t just benefit fireflies, but dozens of other wildlife species that depend on it to survive!

Article by Braelei Hardt, National Wildlife Federation, and Robert Watkins, National Wildlife Federation

https://blog.nwf.org/2024/09/how-fallen-leaves-support-moths-and-butterflies/

Published September 26th, 2024

Amid the crunch of autumn leaves underfoot lies a hidden ecosystem where moths and butterflies find shelter and sustenance. While it might seem like clutter to some, this layer of fallen foliage is a lifeline for various species—including these important pollinators. Fallen leaves are more than just remnants of summer; they are essential components of ecosystems. They enrich the soil, provide habitats, and play a pivotal role in the life cycles of many insects. Let’s take a look at some of the species that depend on the leaf layer for survival.

Mourning Cloak

The mourning cloak butterfly is a remarkable species known for its longevity and unique hibernation habits. Unlike many butterflies that migrate or overwinter in other life stages, the mourning cloak spends the winter as an adult. As temperatures drop, these butterflies seek refuge in the natural crevices provided by tree bark, logs, and importantly, within piles of fallen leaves.

Fallen leaves offers a protective blanket that insulates the butterflies against harsh winter conditions. The layers of leaves help maintain a stable microclimate, shielding them from freezing temperatures and fluctuations that could otherwise be fatal. This insulation is crucial for their survival, allowing them to conserve energy throughout the dormant season. By hibernating in leaves, they can face temperatures as low as -76°F (-60°C)!

When spring arrives, the mourning cloaks emerge, often one of the first butterflies to be seen, as they take advantage of early sap flows and mate before competition arrives. Despite braving the winter, mourning cloaks are the longest living butterflies in North America, often surviving up to 10 months.

Red-banded Hairstreak

The red-banded hairstreak butterfly exhibits a fascinating life cycle intricately tied to fallen leaves. Unlike most butterfly caterpillars, which feed on living plant tissues, the larvae of this species primarily consume decaying leaf material, especially from sumac and oak trees. The caterpillars of this species look like fuzzy leaves to camouflage against their environment.

The leaf layer serves as both a pantry and a protective environment. The layers of leaves conceal the caterpillars from predators and harsh weather, offering a safe space for growth and development. This reliance on decaying matter places the red-banded hairstreak in a unique ecological niche, contributing to nutrient cycling and the breakdown of organic material in forest ecosystems.

Io Moth

Io moths are renowned for their vivid coloration and striking eyespots, which serve as a defense mechanism against predators. After a period of feeding on the leaves of various trees and shrubs as caterpillars, they prepare for metamorphosis by spinning cocoons. This critical stage occurs within the leaf litter on the ground.

The fallen leaves provide essential camouflage for the cocoons, blending seamlessly with the environment to avoid detection by predators. Moreover, the microhabitat within the leaf litter maintains optimal humidity and temperature levels necessary for the delicate process of metamorphosis. The structural complexity of the leaf layers protects the cocoons from physical disturbances and environmental stressors, ensuring that the moths can successfully emerge as adults.

As adults, Io moths do not have functional mouths and do not feed. They live solely to reproduce, with a short adult lifespan of about a week. This means that every stage of their life cycle prior to adulthood is crucial for accumulating the energy reserves needed for reproduction. The protection provided by a leaf cocoon during metamorphosis is vital to their survival and ability to continue the species.

Luna Moth

The Luna moth captivates with its ethereal beauty, showcasing pale green wings and elongated tails. Similar to the Io moth, the Luna moth’s life cycle is deeply connected to the leaf litter. After the caterpillars have fed and grown on the leaves of hardwood trees like hickory, walnut, and birch, they descend to the forest floor to pupate.

Within the leaf layer, the Luna moth caterpillars spin silken cocoons interwoven with leaves, creating a secure environment for transformation. The developing moth may spend anywhere from three weeks to several months overwintering in this cocoon, while they only live as adults for about a week.

Like Io moths, adult Luna moths they do not have functional mouths to feed. This brief window of adulthood is dedicated entirely to reproduction. Because of their short lifespan and inability to feed, conserving energy under the leaves during winter ensures they emerge as healthy adults capable of finding a mate and laying the eggs quickly.

Dead Leaves, Living Habitat

Supporting the life cycles of moths and butterflies has broader implications for both wildlife and human communities. These species play significant roles in ecosystems as pollinators, prey, and indicators of environmental health.

By understanding and preserving the natural processes that sustain these species, such as the availability of leaf layers, we contribute to the resilience and functionality of ecosystems. Healthy ecosystems provide essential services, including clean air and water, pollination of crops, and natural beauty that enhances our quality of life.

So this autumn, as the leaves create a mosaic on the ground, consider the unseen wonders they support. Embracing the natural accumulation of leaves supports the intricate life cycles of species like these moths and butterflies. In doing so, you can help nurture the ecosystems that ultimately sustain both wildlife and human communities.

Banner image by Neil Williamson