The Stealth Caterpillar

August 17, 2014

Nature Notes by Bill Dunson





When caterpillars are toxic, they tend to be brightly colored and some possess painful spines. Tasty caterpillars are usually well camouflaged; some are green to resemble foliage, some mimic bird droppings or twigs, and some have various types of disruptive camouflage. My wife was picking Japanese beetles off her prized blueberry plants and by chance found an interesting example of the disruptive camouflage type, one of the prominent moths, Schizura ipomoeae. Although often called the morning glory prominent, one expert (David Wagner) prefers to call it the checkered-fringe prominent since this species has no special association with morning glories. Indeed it feeds on a wide variety of woody plants and is distributed from Canada to Florida.

Despite being common, this caterpillar is very rarely seen since it has such a spectacular means of blending in with the background vegetation. By variation in both color, pattern and form, it is difficult for a bird to pick this tasty snack out from the plants. You will note from views of the side and top that there is a patchwork of colors and pattern that differ depending on the orientation of the body. The change in body shape, the angles of the dorsal surface, and types of spines also serve to disrupt the ability of a predator to pick this object out as a potential meal. It is indeed a “stealth” caterpillar hiding among the foliage. This camouflage appears to be so effective that it does not appear to have any defenses known from other caterpillars such as toxic spines or scary eye spots.

The adult moth is shown here in a photo by neighbor Bob Perkins, who catches moths on a sheet illuminated by a light at night. It is also well camouflaged but in a more typical fashion that resembles bark.

Evolutionary selection has presented us with a myriad of examples of how prey can elude predators by being camouflaged. But this caterpillar provides one of the more interesting cases of how bird predation can be minimized by using patches of color, pattern and shape.

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

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