Jacksonville Zoo and Gardens

Two-striped Walking Stick

Pseudophasmatidae

Phasmatodea

Insecta

Throughout Florida and around the Gulf Coastal Plain west to Texas

Forested areas with abundant trees and shrubs on which to feed, as well as scrub palmettos. These insects also prefer trees with loose bark to use for shelter.

Anisomorpha buprestoides has a cylindrical body with a long thorax and abdomen. The two yellow-brown stripes run down the length of the body. It has 5 segmented tarsi (feet) on long slender legs, long threadlike antennae, and a tiny head. It has one set of segmented cerci at the tip of the abdomen. It does not have wings. Adults grow to be between 4 and 6 inches long.

Several months

In the wild, they feed on leaves of trees and shrubs; in the Zoo, they are fed primarily wax myrtle and sweetgum browse.

Unlisted

The two-striped walking stick is herbivorous, feeding on leaves of trees and shrubs. They are commonly found on brambles.

A mature male walking stick will attach himself to a female even if the female is not yet mature, to ensure finding a mate. The male uses his cerci to hold on to the female. They will remain together until one of them dies. In the fall, females lay their eggs on or in the ground. When the nymphs hatch they are green and do not turn twig-like until maturity. Anisomorpha buprestoides is fairly unique among the insects in that it can regenerate lost legs.

These insects show gradual or incomplete metamorphosis; they slowly get larger through the growing season, and are most likely to be seen in the late summer and fall.

Stick insects show rocking behavior in which the insect makes rhythmic, repetitive side-to-side movements. Functions proposed for this behavior include the enhancement of crypsis (the ability of an organism to avoid observation or detection by other organisms) by means of the resemblance to vegetation moving in the wind. However the repetitive swaying movements may be most important in allowing the insects to discriminate objects from the background by their relative movement, a visual mechanism typical of simpler animals. Rocking movements by these generally sedentary insects may replace flying or running as a source of relative motion of objects in the visual field.

The ability of this species to defend itself with a particularly odiferous secretion was reported as early as 1835. Eisner (1965) reported that the stick insects generally discharged the secretion as a result of certain perceived threats. They can aim up to 11 to 16 in (30 to 40 cm) with accuracy: “Anisomorpha discharges instantly in response to mild traumatic stimulation as, for example, when individual legs are pinched with forceps, or when the body is tapped or persistently prodded . . . Marksmanship is precise: the spray invariably drenches the particular instrument used for stimulation.” Although most discharges required actual physical contact, Eisner (1965) found that the stick insects often would discharge at birds before being contacted by the bird. In trials, Eisner (1965) found the secretion to be an effective defense against ants, beetles, mice and birds; mouse-opossums (Marmosa sp.), however, managed to withstand the spray and consume the stick insect once its reservoir was depleted (after up to five discharges from the larger females). One to two weeks are required to replenish the depleted reservoirs (Eisner 1965). Carlberg (1985) found that rats (Rattus norvegicus (Berkenhout)) initially were repelled, but some individuals managed to overcome the defense in subsequent attacks.

Phasmatodea, the order name, is derived from the Ancient Greek phasma, meaning an apparition or phantom, and refers to the resemblance of many species to sticks or leaves. Their natural camouflage can make them extremely difficult to spot.

Although Gray (1835) mentioned the defensive secretion of A. buprestoides, the first account of its effect on humans that could be located was by Stewart (1937), who wrote about an incident in Texas: “The victim was observing a pair of Anisomorpha buprestoides . . . with his face within two feet of the insects, when he received the discharge in his left eye. . . The pain in his left eye was immediately excruciating; being reported to be as severe as if it had been caused by molten lead. Quick, thorough drenching with cool water allayed the burning agony to a dull aching pain. The pain eased considerably within the course of a few hours. Upon awakening the next morning the entire cornea was almost a brilliant scarlet in color and the eye was so sensitive to light and pressure for the next forty-eight hours that the patient was incapacitated for work. Vision was impaired for about five days.” Symptoms gradually disappeared and there were no lasting effects. Albert (1947) described a similar but less severe incident.

Recent accounts (Dziedzyc 1992, Hatch et al. 1993, Paysse et al. 2001) report incidents with essentially similar symptoms, the first and most severe involving a dog. In that case, the dog suffered an ulcerated cornea, although the damage could have been self-inflicted after the encounter with the stick insect (Dziedzyc 1992). The recommended treatment includes immediate irrigation of the eye with large amounts of water, followed by administration of over-the-counter analgesics if needed for pain. Medical attention should be sought if more severe symptoms, such as decreased vision or light sensitivity, are present.

Walkingsticks are close relatives to grasshoppers, crickets, palmetto bugs and preying mantids.

Other names applied to these stick insects in general include devil’s riding horse, prairie alligator, stick bug, witch’s horse, devil’s darning needle, scorpion, and the musk mare.

Two-striped walkingsticks were first acquired by the Jacksonville Zoo and Gardens in 2010 and have successfully bred here.

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