HEEL-WALKERS OR GLADIATORS: Mantophasmatodea

PHYSICAL CHARACTERISTICS

Heel-walkers are brown, gray, green, or yellow and are sometimes marked with darker dots or stripes. The sides of their midsection, or thorax, are sometimes spiny. They measure 0.35 to 0.94 inches (9 to 24 millimeters) in length. The males are usually smaller than the females. Both sexes are wingless and resemble young mantids or stick insects. The larvae (LAR-vee), or young form of the animal that must change form before becoming an adult, strongly resemble the adults.

The head is distinct and has chewing mouthparts with sharp jaws that are directed downward. The antennae (an-TEH-nee), or sense organs, are long, threadlike, and have many segments. The compound eyes, each with many individual lenses, are well developed, but simple eyes, those with only a single lens each, are absent. The front and middle legs are slightly enlarged and have two rows of short, sharp spines. The hind legs are slender and lack rows of spines. All of the feet have five segments, but the first three are fused, or joined together.

The abdomen consists of ten well-developed segments and a much smaller eleventh segment. In the females, the eighth and ninth segments have three structures that together form a short egg-laying device, or ovipositor. The tip of the abdomen has a pair of projections. In females these projections are short, but in males they are much longer and curved.

GEOGRAPHIC RANGE

All thirteen living species are found in Africa in Namibia, South Africa, and Tanzania. Two fossil species preserved in amber were found in Russia.

HABITAT

They are found in dry, scrubby habitats that receive little rain. Heel-walkers live down inside tufts of grass or grasslike plants, where they blend in perfectly thanks to their spotted and striped bodies.

DIET

They eat various kinds of insects, including each other, grasping and holding their prey with their strong and spiny front and middle legs. Heel-walkers will eat all but the wings and legs.

BEHAVIOR AND REPRODUCTION

Heel-walkers usually live alone, but pairs of males and females are often found together in the same tuft of grass. Populations are usually concentrated in small patches within a much larger area of suitable habitat. They appear to be active day and night, moving very slowly through the grass. However, they can move quickly to capture prey or while mating. The common name "heel-walker" comes from the fact that as they walk, the clawed tips of their feet are always held up in the air. The males use the projections on special plates located on their abdomens to tap on the ground, possibly as a means of communicating with other heel-walkers.

IN A LEAGUE OF THEIR OWN

Thousands of new insect species are discovered every year. But the last time a new order of insects was discovered was back in 1914. Heel-walkers had been known for more than one hundred years but were ignored by scientists because they closely resembled young praying mantids. In 2001, forgotten specimens of heel-walkers collected in Namibia and Tanzania were discovered in museum collections. In 2002, after careful examination, researchers placed them in their own order, the Mantophasmatodea.

Courtship among heel-walkers is unknown. Males climb up on the female's back to mate, a process that may take up to three days. Females produce several sausage-shaped egg pods, each containing ten to twenty long, oval eggs. The egg pods are covered by a coating of sand mixed with special fluids produced by the female. The coating is shaped by the female's ovipositor and eventually becomes hard. The larvae hatch at the beginning of the rainfall period and strongly resemble the adults. They will molt, or shed their hard outer coverings, several times before reaching adulthood near the end of the winter wet season and die during the following summer dry season. Their life span varies considerably, depending on how much rain falls in the summer and winter.

HEEL-WALKERS AND PEOPLE

Each species of heel-walker lives in a very small area, and their populations are widely separated. The fact that they are distributed this way makes them especially interesting to scientists that study the distributions of animals in southern Africa.

CONSERVATION STATUS

No species of Mantophasmatodea is endangered or threatened. Since very little is known about the species, it is not clear which are threatened by development or habitat destruction. It is very possible that populations, even entire species, living in only a few places could become extinct (ihk-STINKT), or no longer exist, if their habitats were damaged or destroyed. However, some populations appear to be able to survive human activities and have been found right alongside of roads.

GLADIATOR (Praedatophasma maraisi): SPECIES ACCOUNT

Physical characteristics: The gray bodies of gladiators measure 0.8 to 1.2 inches (20 to 30 millimeters) in length. They have round heads and large eyes. The antennae are threadlike and nearly as long as the body. The front and middle legs, as well as the sides of the thorax, are spiny.

Geographic range: They are found in the Karasburg Region, southern Namibia.

Habitat: Gladiators are found near the Orange River, in the Nama Karoo.

Diet: Gladiators probably eat other insects.

Behavior and reproduction: Nothing is known about the behavior and reproduction of this species.

Gladiators and people: This species does not impact people or their activities.

Conservation status: This species is not endangered or threatened. ∎

FOR MORE INFORMATION

Periodicals:

Adis, J., O. Zompro, E. Moombolah-Goagoses, and E. Marais. "Gladiators: A New Order of Insect." Scientific American 287, no. 5 (November 2002): 60–65.

Klass, K., O. Zompro, N. P. Kristensen, and J. Adis. "Mantophasmatodea: A New Insect Order with Extant Members in the Afrotropics." Science 296, no. 5572 (May 24, 2002): 1456–1459.

Picker, Mike D., Jonathan F. Colville, and Simon van Noort. "Mantophasmatodea Now in South Africa." Science 297, no. 5586 (August 30, 2002): 1475.

Web sites:

"Mantophasmatodea (Gladiator) Fossil Insect Gallery." http://www.fossilmuseum.net/Fossil_Galleries/Insect_Galleries_by_Order/Mantophasmatodea/Mantophasmatodea.htm (accessed September 24, 2004).

New Insect Order Discovered for First Time Since 1915. http://www.conservation.org/xp/news/press_releases/2002/041702.xml (accessed on September 24, 2004).

"Order: Mantophasmatodea (Heelwalkers)." http://www.museums.org.za/bio/insects/mantophasmatodea/ (accessed on September 21, 2004).

Trevidi, B. P. "New Insect Found in Southern Africa." National Geographic News.http://news.nationalgeographic.com/news/2002/03/0328_0328_TVstickinsect.html (accessed on September 24, 2004).