Are you what you eat in the Wildlife Garden?

The tale of a yellow caterpillar originally published by Loret T. Setters on August 19, 2011 at (beautifulwildlifegarden.com/).

I found a yellow caterpillar of the Cloudless Sulphur Butterfly (Phoebis sennae) on my Partridge Pea (Chamaecrista fasciculata). I was happy because I do a feature in the monthly issue of The Lily Pad, a newsletter that I write for The Florida Native Plant Society-Osceola County local chapter. The feature is called Before and After, where I feature an insect photographed in it’s larval state and then as emerged in adulthood. I was running out of “befores”.

While eating flower buds, a lovely shade of yellow
While eating flower buds, a lovely shade of yellow

I photographed my find and headed in to make sure I had identified it correctly. Now mind you, it was the third new-to-me caterpillar I found this week, one being an armyworm and the other, some sort of Owlet Moth (Noctuidae) larvae. I am still having a hard time pinpointing the owlet species and I’m sorry that I didn’t collect it when I had the chance. By the time I got back to it, it was long gone.

My Sulphur caterpillar looked similar to others posted at bugguide.net. But some were a horse…ummm…cat of a different color. Insect ID’s aren’t always as simple as one might think. I checked a few different Websites with photos and read, with interest, anecdotal information that caterpillars may change colors based on the part of the plant that they eat. I found another site that specifically mentioned sulphur caterpillars as doing this. When they dine on the flowers, they are yellow, but if they switch to the leaves, after the flowers are spent, well, they turn green. THIS I HAVE TO SEE WITH MY OWN EYES!

Left with only leaves to eat, my caterpillar friend turns green
Left with only leaves to eat, my caterpillar friend turns green

I have often said that I only capture critters when it involves educational study that does no harm, and I felt that this qualifies. I immediately gathered the little yellow cat and a branch of the plant and placed them in a roomy display case (relative to the size of the cat). It was munching away on the flower. I added a small paper towel square dipped in water to maintain moisture and placed the container where it would get brief morning sun, but not so much as to fry the poor thing. The next morning I checked on my guest and (s)he was now munching away on the leaves, and was beginning to look a little “green”. I went out and got a fresh branch of the plant…who likes eating day old food? My charge dutifully climbed onto the fresh greens and I replaced the screening and rewet the paper towel square.

Day four even greener
Day four even greener

Day four, I checked again, and (s)he is even more vivid green. To me this is an interesting phenomenon. There are a lot of caterpillars that are “generalists”— that is, they eat more than one species of plant and I guess they would have color variations based on what plant they choose. An “aha” moment in my occasional problem with identifying cats.

Caterpillars go through various instars and changes to appearance may include coloring. Early instars may match the shade of the fresh young leaves and later instars may become darker to blend in with older leaf coloring.

Early Instar of Banded Sphinx Moth Caterpillar (Eumorpha fasciatus)
Early Instar of Banded Sphinx Moth Caterpillar (Eumorpha fasciatus)
Later instar of Banded Sphinx has quite a different color scheme
Later instar of Banded Sphinx has quite a different color scheme

Have you noticed this in your own wildlife garden?

References::

http://www.learnaboutbutterflies.com/

Plant coloration undermines herbivorous insect camouflage, a research hypothesis (pdf) on plant coloration from Harvard Forest (Harvard University).
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