IS it eating the plant?

Quite often people will ask why a caterpillar that is known for hosting on one plant is eating a different one. Even today, people are discovering new host plants for species. Some eat it only in captivity and others eat it in the wild. But the question we first must ask is, “IS it eating the plant?” Quite often, it isn’t eating it at all.

Caterpillars move off a host plant for several reasons. Some move off to molt, to pupate, or simply are lost, working their way back to their host plant.

A Gulf Fritillary caterpillar molts on a Bahia grass seed stalk
A Gulf Fritillary caterpillar molts on a Bahia grass seed stalk

We’ve seen many species of caterpillars on plants that weren’t their host plants. Almost every time, they were molting or pupating.

A Zebra Longwing pupates on a marigold bloom
A Zebra Longwing pupates on a marigold bloom

Much to our amazement, we found a Buckeye chrysalis on a snail. You never know where they will choose to pupate.

A Buckeye pupated on a snail
A Buckeye pupated on a snail

We had Buckeye butterflies in a screened garden room. To my surprise, they stripped a butterfly bush (Buddleia davidii) of leaves, pupated, and emerged with no problem. Later we found caterpillars on butterfly bush in the wild. Evidently it happens but rarely.

Buckeye caterpillars eating butterfly bush
Buckeye caterpillars eating butterfly bush

Although there was no question whether the Buckeye caterpillars were eating butterfly bush leaves, we did tests, feeding that particular bush to caterpillars in captivity. They ate it with no problem. We tried another butterfly bush, one that bloomed a different color, and they all died. We bought the lavender blooming bush from a nursery without a label. When we returned to the nursery, they had no idea which cultivar it was.

Monarch butterflies often pupate on milkweed. They also often pupate off milkweed.

A Monarch caterpillar pupate on a pipevine leaf (1/3 way down on the right side of the photo)
A Monarch caterpillar pupate on a pipevine leaf (1/3 way down on the right side of the photo)

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