In the Garden:
Southwestern Deserts
May, 2007
Regional Report

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A young swallowtail caterpillar has taken a bite out of this citrus leaf.

Swallowtail Caterpillar

After a recent windy afternoon with just enough rain sprinkles to make plants look dusty, I was preparing to hose off foliage on my young citrus transplant. Then I noticed that a couple of top leaves had been chewed. Peering closely, I spotted a swallowtail caterpillar. If I didn't know what I was looking for, I may not have recognized it as a caterpillar. Barely 1/4 inch long, it was yellowish brown and white, looking like a shiny blob of something potentially gooey.

Several days later it had doubled in length and girth and its coloration was darker. As it continues to grow and shed four or five exoskeletons, it will more closely resemble a large black and white bird dropping. What a clever way to disguise oneself from predators!

Favorite Host Plant
Citrus leaves are the preferred food for various swallowtail species, including giant swallowtail (Papilio cresphontes), which I think is the caterpillar on my plant. According to Caterpillars in the Field and Garden (Oxford University Press, 2005; $29.95), this caterpillar species is the most likely of all the citrus swallowtails to be found in gardens that offer its preferred host plants.

I've never grown citrus in my backyard due to lack of space. But I was browsing a nursery this spring and spotted very healthy-looking citrus seedlings in narrow, foot-long rooting containers and thought it would be easy to pot one up into a larger container with minimal stress to the root system. Just for fun. It's amazing how quickly an adult butterfly found that citrus in my backyard and deposited eggs. I wish I'd seen it, because giant swallowtail butterflies are magnificent, measuring up to 5-5/8 inches.

Since acacia seeds are dropping, there are loads of birds visiting the garden lately. I check for the caterpillar whenever I walk by the citrus, and although it's perched on the top leaves, it has been left alone. Perhaps its camouflage system is really working!


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