Let fallen leaves be
I’m a bit of an anomaly on my street, but my neighbors have gotten used to it. They now welcome the fact that I’ll eagerly accept their bags of raked-up leaves and pine needles, a.k.a. “yard waste.” For me, these things are gold. The pine needles make an attractive mulch under the trees and shrubs out front. The leaves get spread out under the trees along the back property line.
I first started collecting neighbors’ leaves to help suppress weeds in what is a rather large area. It took me a while to realize that left to decompose, the leaves turn into soft, nutrient-rich humus. And here, as I’ve learned just recently, a little magic occurs.
If you’ve been fortunate enough to attract butterflies to your yard, you may have noticed that the larvae maturing on their host plants suddenly go missing. I had always assumed that they disappear into a bird’s belly. But while caterpillars do make great food for birds and other predators, it’s more likely that the mature larvae have walked off of the host plant to find a site to pupate. I’ve watched that phenomenon many times just this month, as the black swallowtail larvae I collected from my rue plants and placed into protected habitats, walked off to go into chrysalis stage elsewhere, either on the side of the container or on one of the sticks I placed inside.
In his book, “Nature’s Best Hope,” entomologist Doug Tallamy explains why caterpillars leave their host plant at such a critical moment. “The longer a caterpillar stays on its host, the greater the chances it will be discovered and attacked by one of its enemies. By crawling some distance from its host plant before it pupates, the caterpillar has decentralized the effective search zone... Instead of caterpillar predators being able to search just a few square feet for their prey, they must search thousands of square feet, a low return task that is usually not worth the time or energy involved.”
One of the places that many moth caterpillars go to pupate is leaf litter. More from Tallamy: “Your yard may include an oak tree that can feed hundreds of caterpillars, but more often than not, that oak will be surrounded by mowed lawn growing in compacted soil. When your caterpillars drop from the tree, they will find no leaf litter in which to spin their cocoons...” In other words, it’s not enough to grow host plants to feed mature moths and butterflies, and their larvae, if there’s no place for them to continue their life cycle. Leaving leaves on the ground can help.
There are hundreds of butterfly and moth species native to Pennsylvania. Few are as noticeable as monarchs and swallowtails, and I’m surprised at how few I know. My friend Carol Breslin sent me a photo last week of what looked like a black “wooly bear” caterpillar. She’d noticed it on the pavement of a parking lot in Exton. Did I know what it was? Breslin I.D.’d it first: Giant Tiger Moth. “I’ve lived in this area for 18 years and never seen this kind of caterpillar,” she told me. Likewise, this past summer I saw my first Red Underwing Moth, though I’ve lived on my property for thirty-five years. Another species that I’d never heard of.
How can we protect species if we don’t even know they’re out there? Leaving nature more natural is a good way. Longwood Gardens also offers these tips:
“Turn off bright exterior lights at night, or switch to insect-friendly LEDs.
“Relocate your fallen leaves (which may hide overwintering cocoons) instead of burning or shredding them.
“Carefully inspect your shrubs for cocoons before trimming them in the fall.”
Have you seen any unusual moths or butterflies recently? I’d love to hear about them.