Caterpillar Camouflage

Caterpillars Use a Variety of Deceptive Techniques to Hide From Predators

By Renn Tumlison, tumlison@hsu.edu and Kristen Benjamin, benjamk@hsu.edu

 During the spring and summer, moths and butterflies produce large numbers of offspring, which is necessary because those offspring – caterpillars – are food for many other animals. Birds remove large numbers of the plump, juicy larvae as they forage along branches of herbaceous vegetation, as well as trees. As a result of the heavy predation pressure, very few of the larval insects actually make it to the winged adult stage. The strategy of the butterflies and moths has to be: lay a lot of eggs to increase the chances that a few will become adults of the next generation. 

Io Caterpillar

 Caterpillars of different species employ a variety of tactics to survive their larval stage. Some are covered with toxic spines to defend against a predator, such as the Io Moth Caterpillar (left).

Others try to mimic some aspect of the environment in order to deceive a potential predator. The approach to deception is quite varied for the species that use that tactic. The color and posture of this "inchworm" mimics a broken twig. 

Twig Mimic
Headshot Snake Combo

Imitation of a potentially dangerous aspect of the environment is a good approach. For example, the mature caterpillar of the spicebush swallowtail butterfly (Papilio troilus- top image) is a relatively large animal with a small head tucked underneath the fleshy anterior end. When disturbed, the caterpillar tucks its head further underneath the body and swells out its anterior end, expanding a colorful area containing “eyespots,” so the area mimics the head of a snake (bottom image). Birds initially seeing the caterpillar as a meal may reinterpret their find as one of their own predators (some snakes eat birds) and leave the area.  

Birds are common, and in vegetated environments, their numerous droppings commonly are found lying on leaves. Predators typically do not interpret bird droppings as a preferred source of food, so those remains are ignored by foraging animals. For the caterpillar that spends its life feeding on leaves, imitation of bird droppings is a useful mechanism of disguise. Butterflies of the genus Limenitis, such as the red-spotted purple and viceroy, have well developed that mechanism of deception. Compare the caterpillar (left image) with the actual bird dropping (right image). 

Long Birdpoop Combo
Schizura on Redbud Camo

The leaf itself is an aspect of the environment that can be mimicked. The caterpillar of the morning glory prominent (Schizura ipomoeae) has mastered that deception. A green band in the thoracic region of the caterpillar separates the brownish-gray head and abdominal regions. The caterpillar eats out a notch along the edge of a leaf, then positions itself in the notch. 

The green band disrupts the form of the caterpillar as it blends with the color of the leaf, and the brown portions of the larva look like the curled, dead edge of a leaf. The effect is complemented by a few spines and bumps along the back of the caterpillar.

Schizura on Redbud
Wavy-lined Emerald Caterpillar

Some caterpillars don’t resemble an aspect of their environment, so they become camouflaged by adding some of the environment to themselves. The caterpillar of the wavy-lined emerald moth (Synchlora aerata) is given its own name – camouflaged looper – because of its adaptive form of deception. 

Often, this species is found on flowers of the composite family, such as black-eyed susans. Along its body, the caterpillar adorns itself by attaching chewed bits of the flowers upon which it is feeding. This behavior gives the advantage of being able to blend well with a variety of different plants. 

Wavy-lined Emerald Caterpillar Detail
 
 
 
 
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