Wild Silkworms

Wild Silkworms

Part of Ep. 402 Planting Beauty for Your Yard and Garden

Join Entomologist Phil Pellitteri and learn about the wild silk worm, an insect that can be quite startling but doesn't really cause any problems.

Premiere date: May 31, 1996

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley:
This is the time of year when we're visited by unfamiliar animals, insects and birds. But just because you don't recognize something doesn't mean it's going to cause a problem. I'm with UW-Madison Extension Entomologist Phil Pellitteri. We're talking about an insect that can be quite startling but doesn't really cause any problems.

Phil:
These are the wild silkworms. There are four species. They are the most impressive and largest insects that we typically see. What I have is the cocoon stage of the cecropia moth which you might find in a lilac bush or an apple tree. That's how the insect gets through the winter. And long about the first couple weeks of june then we start seeing the adult moths coming out.

Shelley:
What about this one that you handed me? This is a lot smaller. That's harder to find.

Phil:
That is from polyphemus, and crawls down into the ground and spins it's cocoon on the soil surface. It's not as obvious as the cecropia. Both of these are just sitting there not harming any plants in our yard. This is the transitional stage from caterpillar to adult moth. What catches people's attention is the caterpillar because it's so big. I have a dried specimen of a cecropia in my hand. They get to be about four inches long. You usually see them in the late summer probably looking for a place to spin a cocoon.

Shelley:
That is intimidating. My first reaction would be, "I don't know what this is but is it harming my garden?"

Phil:
They eat a few leaves, but it doesn't hurt much. We want them around because the adult moths are impressive. The rewards are great. These are both the same species. Their size differs depending on diet. These are very short lived; they only live for a day or two. They don't feed at all. They don't even have functional mouth parts. They search out mates, flying as much as a mile and a half. But the birds and the bats find them to be great food so they don't last very long in nature.

Shelley:
Where are we likely to find these?

Phil:
Either you'll find one crawling out of a cocoon-- or, they're attracted to light so, you might see one on the garage or siding because they've been resting there. With no mouth parts, they're not going to harm our yard, either. Absolutely harmless. You said, that's the most common but these are some of the other ones we might see. We do have three other common species. This is the luna moth. This is polyphemus. The males have great big feathery antennae that they use to find the females. The female's antennae are smaller.

Shelley:
It looks like a bigger moth.

Phil:
Here, we have a promethea the male and female are different. We call this dimorphic. The female is lighter and the male is darker. Not nearly as pretty.

Shelley:
What about this guy? Is he part of the same group?

Phil:
This type silkworm is called a buck moth. It's a day-flying moth in the northern part of the state typically associated with willow and dogwood in marshy areas.

Shelley:
So, these are something we should be watching for. Especially if you show the kids how impressive these can be. Thanks, phil.
So, if you see these in your yard don't panic and don't destroy them! They're worth enjoying.

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