If you’ve been cleaning around the flower beds or raking back mulch at the base of a tree and found little brown, hollow “creatures” clinging to bark or lying in the soil, I can understand the shiver that runs up your spine. The first time one of my grandsons brought me a handful of them from under an old maple, he held them out like treasure and asked if we had aliens in the yard. Truth be told, they do look eerie at first glance—papery, leggy, and perfectly shaped, as if some insect simply stepped right out of its own skin and vanished.
What you’re almost certainly looking at are cicada shells, also called cast skins or exoskeletons. They’re a perfectly normal sign of a healthy yard with established trees, and while they may look unsettling, they’re harmless. In this article, I’ll walk you through exactly what they are, how to identify them, why they collect around tree bases and garden beds, whether they can hurt your plants, and what to do—if anything—about finding them.
1. What those brown husks actually are
Those “hollow insect armor” pieces are the shed outer skins of cicada nymphs. A cicada spends most of its life underground, feeding quietly on fluids from tree roots. When the nymph is ready to become an adult, it crawls out of the soil—often at night—climbs a tree trunk, post, raised bed edge, or even the side of the house, and then splits open its old shell.
The adult cicada emerges soft, pale, and almost ghostly at first. Over the next several hours, its wings expand and its body darkens. What gets left behind is that dry brown shell: an exact little mold of the insect’s former body, usually 1 to 2 inches long, with hooked front legs and a split down the back where the adult came out.
2. How to tell a cicada shell from something worse
Cicada shells have a very distinct look. They are light brown to medium chestnut brown, crisp and hollow, with six legs, big side-set eyes, and strong front claws built for digging. If you turn one over in your hand, it weighs almost nothing. The back usually has a neat crack or opening from the top of the thorax down toward the middle, which is where the adult emerged.
They’re often mistaken for dead insects, beetle remains, or even signs of a plant pest outbreak. But unlike rotting insect bodies, cicada shells are dry, clean, and odorless. You won’t find any soft tissue inside. They’re more like a little paper costume than a carcass.
3. Why they turn up at the base of trees
Cicada nymphs live underground near tree roots, sometimes for 2 to 5 years in annual cicada species, and in the case of the famous periodical cicadas, 13 or 17 years. Mature trees are prime real estate for them because the roots provide a steady food source over many seasons. That’s why the shells so often collect at the base of oaks, maples, elms, fruit trees, and old shade trees.
If you’ve been pulling weeds or freshening mulch in beds around the trunk, you’re right in the spot where they would have emerged. A single mature tree can have dozens, and during a heavy emergence year, even hundreds, especially within 2 to 6 feet of the trunk where the upper roots spread through loose soil.
4. Why they look so creepy and so perfect
Nature can be awfully dramatic. The reason these shells look “exactly like hollow insect armor” is that they are an exoskeleton—the hard outer body covering the cicada wore while it was underground. Insects don’t have bones inside the way we do. Their support structure is on the outside, so when they molt, they leave behind a full-body shell.
I remember finding them on the trunks of our apple trees as a girl and being amazed that every little detail remained: the legs, the eye bumps, even the tiny clawed feet. To a child, it looks like a whole bug frozen in place. To an old farm cook like me, it still looks a bit spooky every time, especially in the early morning when the dew hasn’t dried yet.
5. Where you’re most likely to find them in the yard
Tree trunks are the classic place, but not the only place. Cicada nymphs climb the nearest vertical surface they can manage. I’ve seen shells attached 6 inches off the ground and I’ve seen them 5 feet up on rough bark. They’ll also cling to fence posts, tomato cages, brick foundations, watering cans left outside, deck steps, and the wooden sides of raised beds.
In garden beds, you may find them tucked into mulch, under hosta leaves, around landscape edging, or lying in the soil after wind or rain knocks them loose. If your mulch layer is 2 to 3 inches deep, they can be especially noticeable because that brown shell color stands out against darker composted bark.
6. Are they harmful to your tree or flowers?
The shells themselves are completely harmless. They do not bite, sting, spread disease, or damage roots, bark, or blossoms. They’re simply leftovers from a natural life cycle. You can leave them in place, toss them into the compost, or sweep them away if the look of them bothers you.
The cicadas that made them generally do very little harm to established trees. Adult cicadas may lay eggs in pencil-width twigs, which can cause some tip dieback on young trees or shrubs. On a mature oak or maple, that’s usually just a minor cosmetic issue. The shells you’re seeing are not feeding on your plants now; they’re empty.
7. What cicada nymphs were doing underground all that time
This is the part folks often don’t realize. Before you ever noticed those shells, the cicadas spent years beneath your feet. The nymphs hatch from eggs laid in twigs, drop to the ground, and burrow into the soil. There they feed on fluids from roots using straw-like mouthparts. They are not chewing roots to pieces the way a grub might chew a lawn.
In well-established landscapes, this underground feeding usually causes little to no noticeable damage. If you have large shade trees that are 20, 30, or 50 years old, they can support a cicada population without complaint. It’s one more quiet rhythm of an old yard that most of us only notice when the shells appear.
8. Why you may be seeing more of them this year
Some years are simply bigger cicada years than others. Warm soil temperatures trigger emergence. Once the soil about 8 inches down reaches roughly 64 degrees Fahrenheit, many cicadas begin climbing out. A stretch of warm, damp evenings in late spring or early summer can suddenly bring them on in numbers.
If your area is having a local emergence, or if you’ve had mild weather and healthy mature trees, you may notice many more shells than usual. In years with a major periodical brood, the numbers can be remarkable—dozens on one trunk, piles along mulch edges, and their singing loud enough to fill the whole afternoon. In ordinary annual years, you may find just a handful at a time.
9. How to know if it’s a shell or a live cicada
A shell will be dry, brittle, and empty. If you gently squeeze it between your fingers, it crushes easily. The inside will be hollow, and the back will be split open. A newly emerged adult cicada, by contrast, will be plump-bodied, soft at first, and not brown and papery. Fresh adults may look pale green, cream, or white before darkening over several hours.
If you find one clinging to a shell with soft wings still unfolding, leave it alone if you can. That transformation takes time, often 30 minutes to several hours, and it’s one of the lovelier sights in a garden once you know what you’re looking at. I’ve stood at dusk with a cup of tea and watched it happen on a lilac stem, and it turns something eerie into something wondrous.
10. What to do if you want to clean them up
If they bother you, cleanup is easy. Wear garden gloves if you’d rather not touch them directly, then brush them into a bucket, dustpan, or trug. Around the base of a tree, a hand rake works well. In bark mulch, I usually just pick them out one by one while I’m weeding. They’re lightweight and come loose easily.
You can dispose of them in the compost pile, put them in yard waste, or simply scatter them into less visible parts of the garden where they’ll break down over time. There’s no special sanitation needed. They are not an infestation residue like termite wings or roach skins inside a house would be.
11. When you should pay closer attention
Most of the time, cicada shells are nothing to worry about. But if you have newly planted trees—especially ones under 1 1/2 inches trunk diameter—or small fruit trees just getting established, adult cicadas can sometimes damage tender twigs when laying eggs. In those cases, it can help to cover the canopy with fine garden netting during the few weeks of heavy adult activity.
If you’re seeing branch tips flagging, meaning the ends are browning and drooping like little shepherd’s hooks, that could be egg-laying damage rather than the shells themselves. Even then, mature trees usually recover well. Young trees just need a bit more protection and patience.
12. Common look-alikes people confuse with cicada shells
People often mix them up with beetle molts, dragonfly nymph shells, or even wasp nests broken into pieces. Dragonfly nymph shells are usually found very close to water—pond edges, creek rocks, or water garden plants—because dragonflies emerge from aquatic larvae. Cicada shells, on the other hand, are mostly around trees and dry garden soil.
They’re also different from Japanese beetle grubs or June bug remains, which tend to be found as white or tan larvae in the soil rather than intact brown shells attached to bark. If it looks like a tiny brown bug-shaped shell with a split back and strong front digging legs, cicada is the best answer nine times out of ten.
13. Why gardeners in older neighborhoods see them more often
Older properties often have larger, deeper-rooted trees and less soil disturbance over the years. That gives cicadas the long, stable underground conditions they need. A 40-year-old maple in a quiet yard is a better nursery than a newly graded lot with young ornamental trees and compacted subsoil.
That’s why country places and old-town neighborhoods can seem full of them. Here where I live, the oldest windbreak trees and yard maples host the most shells. Newer subdivisions with skinny saplings planted 8 feet from the sidewalk tend to see fewer at first, though that can change as the landscape matures.
14. A good sign, even if it gives you a start
As odd as they look, cicada shells often point to a living, settled landscape. They suggest your soil has supported insect life for years, your trees are established enough to host it, and the seasonal cycle is carrying on as it should. In a world where so much in nature feels quieter than it once did, I try to take that as good news.
So yes, those creepy brown alien husks are strange-looking. But they’re not dangerous, not a sign of rot, and not something crawling out to attack your petunias. They are simply cicada shells—the empty outer skins of insects that have finished one stage of life and moved on to the next. Once you know that, they seem less like something from a science fiction picture and more like one of the garden’s little marvels.