Garden Q&A: What is this oval pod on my shrub?

Q: What is this papery oval pod on my shrub? I could be imagining it but I think it moves and makes a little rustling noise too. At first I thought it was a seed pod, but it’s the only one. I don’t recall anything chewing on this plant last year.

A: That is the cocoon of a Saturniid moth, such as Luna, Polyphemus, or Tuliptree. They’re spun from dense silk and are generally pill-shaped. Some species in that moth family attach their cocoons to plant stems while others sit loosely in leaf litter, usually wrapped within a dried leaf itself to better blend in. (A good reason to keep those fallen leaves!)

This moth group includes the largest species in North America and are ever-popular with the lucky people that chance upon them because of their beautiful wing patterns, fuzzy faces, and enormous caterpillars. The caterpillars of the type you found don’t feed in groups, aren’t plant pests, and are a rare and joyous find in the garden. The adults have vestigial mouthparts and cannot feed, and only live about a couple of weeks. Too often, night lighting (which disorients and distracts the nocturnal adults trying to find mates) and pesticide use (such as sprays to manage pest caterpillars like Spongy Moth) reduces their survival rate. Like many caterpillars will do, the one which formed your cocoon wandered off its host plant when it was ready to pupate, so it was almost certainly eating something else in the area before it settled-down for the winter on that shrub. They do this in part to avoid detection by predators in this more vulnerable state. A shade tree like oak, maple, sweetgum, willow, hickory, or walnut is a likely contender for its host plant.

If you can leave the cocoon where it is, it’ll probably hatch in a month or less, depending on temperature trends. If the cocoon already has a large hole in one end, then it’s old and the moth emerged sometime last year. Since you’re hearing noises, I’m guessing it’s still intact and fresh. A live pupa tends to wiggle when disturbed or jostled to discourage predators or parasitoids, and that may be what you’re hearing from inside the cocoon. It’s possible it’s parasitized already, as it’s a common occurrence, but that’s a natural factor in the life cycle of these insects and such wasp parasitoids can provide handy pest control in the garden.

Q: Last year I had a bunch of ants in my lawn … I saw their little soil piles so I assume it was ants. Is there something I can do this year to keep them from coming back?

A: Not exactly, and they probably never left, actually, even if the mounds atop their nest entrances aren’t visible . Ants don’t harm the grass and are great to have in the landscape because they are predators of a wide variety of insects that we consider pests. (Including helping to suppress termite activity, so that’s a bonus.) Not only do ants not consume or damage the grass, but their tunneling as they nest helps to aerate the soil to the benefit of plant roots and general soil health.

I don’t recommend treating the yard to get rid of the ants, nor would it be practical or very effective to try. Plus, many chemicals used in general lawn insect control are broad-spectrum and thus can negatively impact beneficial insects as well. Speaking of beneficial, it’s possible that the mounds you saw were due to the activity of ground-nesting bees, which comprise the majority of our locally-native species. Their active period is relatively brief and they don’t bother people, so should be left alone if at all possible. If the soil is loose and the piles appeared in summer and looked like they were kicked-out to one side, it might have been Cicada Killer wasp burrows instead, which are also harmless.

If you still want to discourage the digging and soil mounding, regardless of which creature is responsible, then it’s likely the lawn could use some filling-in to be more dense. For cool-season grasses like fescue, overseed around late August so you can establish a lusher lawn, which covers more of the soil surface and makes the lawn overall less appealing as a nesting site. While you could overseed in spring, it’s a more challenging process fraught with weed competition and difficulties in keeping the fragile seedlings thriving in fluctuating weather and conditions that can make regular irrigation difficult.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Extension” to send questions and photos.