Megaphasma denticrusGiant Walkingstick

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Geographic Range

This species is found in woods, forests, and grasslands of the Southern United States. It exists particularly in Texas, but is found as far north as Indiana and Iowa as well as neighboring states such as Oklahoma, Arkansas, and Louisiana. (Milne, 1980)

Habitat

This species is found throughout woods, forests, and grasslands. They prefer a moist environment, due to the fact that drier weather is unfavorable to the hatching and survival of their eggs. They are generally found on trees or shrubs. (Milne, 1980)

Physical Description

Megaphasma denticrus is an excellent example of the evolution of mimicry. Mimicry is the superficial resemblance of one organism which gives the mimicking organism some advantage or protection from predators. Using mimicry, the walkingstick closely resembles the twig of a plant when motionless and goes virtually unnoticed by predators. Both male and female adults are slow moving and wingless. There is sexual dimorphism, as the male is much smaller than the female. Both are large and elongated, ranging from three to six inches (68 - 108 mm) in length. Adult organisms of this species possess a greenish to reddish brown color with often pale legs. A large pair of antennae are located at the anterior end of the organism which the organism uses for sensory purposes. Immature stages of the organism, referred to as nymphs, resemble adults but are much smaller. Adults and nymphs both have chewing mouth parts that are used to eat various leaves and shrubbery. (Milne, 1980)

Reproduction

In this species, males are extremely rare, sometimes with as few as one male per 1,000 females. In mating, the male holds the female abdomen by a pair of terminal claspers and the eggs are laid as copulation takes place. The females lack well developed ovipositors so they cannot insert their eggs into host plant tissue. Rather, the females deposit up to 150 eggs which are randomly dropped to the forest floor from trees or branches above. Hatching generally occurs in late spring. In the South, the eggs hatch the following spring but in the North, hatching occurs primarily in the second spring. After four to five molts by the young nymphs, adults will emerge in late summer, mate, and then lay eggs until the cold weather sets in. After four to five molts by the young nymphs, the adults will emerge in late summer, mate, and then lay eggs until the cold weather sets in. The metamorphosis of this species is quite simple: an egg changes into a nymph, and a nymph changes into an adult. (Borror and White, 1970)

Behavior

Megaphasma denticrus hide during the day by resting on twigs which they closely resemble. This camouflage protects them from birds and other animal predators. This species is nocturnal and feeds on leaves throughout the night. When feeding, the entire leaf blade, except for the base of the stout veins, is eaten. Because this species does not fly, the infestations are often localized and spread only a few hundred yards during the season. (Arnett, 1985)

Food Habits

This species tends to feed on foliage of grasses and woody plants, especially on grapevines and oaks. It will also feed on leaves of trees and can occasionally cause deforestation. After hatching from their eggs in the springtime, young nymphs feed mainly on understory shrubs. Among the adults, several host plants are primarily fed upon such as the basswood, the birch, dogwood, hackberry, hickory, oak, pecan, and wild cherry. (Drees and Jackman, 1998)

Economic Importance for Humans: Positive

One benefit for humans that this species donates is that they are never abundant enough to really do too much serious damage to their forest foliage. (Milne, 1980)

Economic Importance for Humans: Negative

This species can feed on the leaves of many household favorite plants. In the South, severe outbreaks have only occurred in the Ouachita Mountains of Arkansas and Oklahoma. Many branches and leaves are either killed or die back in heavily defoliated stands as a direct result of the feeding by this species. Furthermore, these insects create a nuisance in high use areas such as parks and recreational areas. (Arnett, 1985)

Conservation Status

The virtually undetectable presence of this species by humans has led to their continued reproduction and expansion throughout the Southern United States. (Milne, 1980)

Other Comments

One interesting fact about this species is that if it loses an arm or leg to a predator or any other threatening factor, it is able to regenerate and grow the lost limb back. (Arnett, 1985)

Contributors

Jon Broyles (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Arnett, .. 1985. American Insects. New York, New York: Van Nostrand Reinhold Comany, Inc..

Borror, .., .. White. 1970. A Field Guide to the Insects. Boston, Massachusetts: Houghton Mifflin Co..

Drees, .., .. Jackman. 1998. A Field Guide to Common Texas Insects. Houston, Texas: Gulf Publishing Company.

Milne, .. 1980. The Audubon Society Field Guide to North American Insects and Spiders. New York, New York: Alfred A. Knopf, Inc..