Illinois Natural History Survey - University of Illinois

Species Spotlight: Walking Stick

Susan Post, Center for Economic Entomology

During the late 1800s the common walking stick, Diapheromera femorata, was such an abundant and destructive insect pest in Illinois that entomologists considered it economically important. Large populations of walking sticks stripped foliage from trees and underbrush and hung from bare twigs and branches in great clusters. A single walking stick could devour an inch-long, one-third-inch-wide strip of leaf in an hour. As forest feeders, walking sticks have preferred the leaves of hardwood trees, especially wild cherry, black locust, and oak. Today, walking sticks are not found in massive groups in Illinois but are still fairly common. They are curiosities that the average person will likely never see because of their excellent camouflauge.

Walking sticks are related to grasshoppers, crickets, mantids, and cockroaches. Modern-day taxonomy places them in the insect order Phasmida. Illinois has five species of walking sticks with Diapheromera femorata, the common walking stick, the predominate species.

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The common walking stick, Diapheromera femorata.

Walking sticks have elongate, cylindrical (sticklike) bodies with long slender legs and antennae. They usually have no wings and range in color from greenish to gray to brown. They move very slowly and sometimes remain motionless, appearing dead for long periods of time. With their camouflage and by feeding at night and resting during the day, walking sticks are rarely detected by other animals. If they should be sighted, the insect straightens out with its front legs and antenna extended to resemble a dead twig.

The common walking stick has incomplete metamorphosis--its life cycle consists of egg, nymph, and adult. The female will lay about 100 small (less than 3 mm in length), long, oval eggs that resemble plump beans. Females simply drop their eggs onto the forest floor while moving in the tree tops. During the early 1900s when the insect was common, the sound of the abundant eggs dropping in the forest was like the constant patter of rain. While the unprotected eggs would seem to be easy targets for parasites or predators, a species of ant is attracted to them and carries them off to their underground nests. The ants don't eat the eggs but instead consume an edible appendage on the eggs called the capitulum. The eggs still hatch normally after they have been dispersed and protected by the ants.

The eggs remain in the ground all winter and most will hatch during May. When first hatched, the young nymphs measure 4.5 mm and are a pale yellowish green. They will molt five times, and by August the walking stick nymphs have reached adulthood. The only changes from nymph to adulthood are increased size and a color change. Young nymphs are green to blend with vegetation; when the foliage begins to change, the nymphs' color changes to various shades of gray or brown. During nymphhood these insects can do something no other immature insect species can--they are able to regenerate lost limbs. At the time of a molt, the limb will be restored although it is sometimes smaller than the original.

As the insect matures, it moves higher into the forest canopy from the shrub and small tree layer to the tops of big trees. Finally, when the eggs begin raining, astute observers will know that a new generation of walking sticks has begun.



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