There are over 100 butterfly species that can be observed in Wisconsin and over 1600 moth species. Butterflies are often welcome visitors to backyards in the warmer months in Wisconsin. They pollinate plants which helps plants diversity and food production. All those butterflies and moths start as caterpillars.
PJ Liesch is an extension entomologist at UW-Madison. He shares tips on how to identify, observe and care for caterpillars in your backyard.
This conversation has been edited for length and clarity.
Becky Mortensen: If someone does spot what they think is a caterpillar in their yard, what is the best way to identify that caterpillar?
PJ Liesch: Sometimes you will bump into a caterpillar that can be very conspicuous and can be easy to identify through various field guides and guidebooks. But there are also some apps that can do a decent job at identifying insects. I will say, though, there are a lot of caveats associated with identifying insects such as caterpillars. The first is that the field guides tend to show the common species and so if you bump into something that is uncommon or rare it's probably going to be a lot harder to identify.
What are some of the most common types of caterpillars that someone might find in their yard?
You almost have to ask the question: what is the commonest type of caterpillar for a specific type of plant? Because most of our caterpillars are going to be host plant specific. As a common example, one insect that we're all generally gonna be familiar with and we know the host plant that it's associated with would be monarchs and milkweeds. You're not gonna find monarch caterpillars feeding on a maple tree or a blueberry bush or an oak tree or anything like that. They're very specific. If you don't have milkweed in your yard, you're just not gonna be bumping into monarch caterpillar.
Once you've spotted and identified a caterpillar, what are some of the best practices for how to observe them and maybe create the best environment possible for them to hopefully eventually become a butterfly?
If you find one caterpillar and you're particularly interested in it, it makes sense to maybe bring that indoors in a container if you wish. You will have to provide it with fresh food from the host plant that it was found on. They will generally get their moisture that they need from the plant foliage that they feed on. Another option would be to either leave them in place on the plants, let them do their natural thing out in nature so they can be exposed to the environmental cues, sunset times and things like that. If you are concerned about them possibly falling prey to a predator parasite outdoors, another consideration would be to get like a mesh bag or mesh sleeve that could be placed over part of the plant. That way it has some protection.
What can people expect to see while observing a backyard caterpillar? What kind of things should people look for as time goes on?
They would start out as an egg, generally laid on a host plant. Out of the egg, you'd get your very small caterpillar, which initially might be a millimeter or a couple of millimeters long. Long story short though, you have the caterpillar larvae, they feed, feed, feed, grow and develop. They get to that pupal stage. Depending on the species, if it's a butterfly, we call the pupal stages a chrysalis. Those are usually in exposed locations, often on the plant or in the nearby surrounding areas. If it is a moth, it may form a cocoon on the planter in the nearby area. Many moth species will actually go down to the soil, burrow into the soil a little bit to pupate.
What are some man-made hazards that could cause harm to caterpillars?
The most direct impact would be the use of pesticides. If you are using insecticides in your yard, if they are either applied directly onto plants that the caterpillars are feeding on, or if they're applied to the nearby area and drift onto plants where those caterpillars are, that could very directly pose some risks to those caterpillar. There's been some research out of the UK that looked at things like streetlights and it turns out that can have some subtle but important impacts on the adult moths, but also caterpillars in their area, because it's just throwing off their general behavior. So if you were to look at an area with a bunch of streetlights compared to areas that are dark, the insects tend to do better where it's going to be dark.
If there are others like me who want to attract caterpillars to their yard, what are some of the best ways to do that?
So one of the best approaches is to put out the particular plants that those caterpillars need to feed on to complete their life cycle. If there's a certain species you're really interested in or you wanna help, you're going to have to incorporate some of the necessary plants for the caterpillars. Another approach would be to put out a wide range of nectar plants, you may be providing resources for the adults. In general, the greater the plant diversity you have in your yard, you're simply offering more items on the buffet, so to speak. And so if you have those picky eaters, but you have their host plant, that is gonna increase the chances that they show up and an adult female lays eggs on those particular plants. So again, having a diversity of plants in your yard can be one of the simplest things that you can do.
