What Are Host Plants?

What is a host plant?

Host plants are plants that an organism lives on and lives off of. Think of the pickiest eater you know. They might not like a wide variety of foods, but they probably still eat more than one thing. Imagine only being able to eat one thing. That’s what it’s like for insects who have a specific host plant! The most common host plant people think of is milkweed, which is a host plant for monarch caterpillars. This photo is of a monarch egg on a milkweed leaf.

Guiding Question: Why do you think the monarch laid her egg on the milkweed? Why is milkweed important to the monarch caterpillars? Would it be okay if she had laid it on another plant, or on the ground? Why or why not?

Caterpillars in your garden!

(Disponible en español)

There is a big crossover between the types of plants we typically grow in vegetable gardens and the plants that insects have as host plants! Black swallowtail caterpillars are a common sight in gardens because their host plants include carrots, dill, and fennel. The cabbage white caterpillar feeds on cabbage, broccoli, cauliflower, and mustard. The tomato hornworm feeds on tomatoes, potatoes, and eggplant.

Teaching Tip: Explore caterpillars some more with your young reader with this bilingual book, “It’s a Caterpillar! (“¡Es una oruga!”).

Meet the dogbane beetle!

This beautiful iridescent beetle is the dogbane beetle! As you might guess from its name, dogbane is its host plant. Although the dogbane plant has poisonous compounds in it, the dogbane beetle has the ability to eat this plant without being harmed! Bug expert Allen introduces us to this cool beetle in this video.

Let’s play plant part tag!

(Disponible en español)

Our Summer Camp team came up with this fun game, and we wanted to share it with you! This game is a fun and active way to think about plant parts with your young scientist. Click here for instructions in both English and Spanish.

Guiding Question: Did any plants have different parts? Were any plants missing these parts? Why might that be? How could we learn more?

Design a garden!

(Disponible en español)

Let’s explore some local host plants (and the species that rely on them) and create our own butterfly garden! Click here to learn about some Illinois species and host plants, then click here to download our garden design handout in both English and Spanish!

Behind the Scenes

Earlier this week, Dr. Allison released some smooth greensnake headstarts as part of our conservation partnership with Lake County Forest Preserves. Although it looks like this adorable snake is smiling, it’s actually doing a defensive display! Learn more about our work with this species here.