TIMEMAS AND STICK AND LEAF INSECTS: Phasmida

PHYSICAL CHARACTERISTICS

Most phasmids are long, smooth bodied, and are colored green or brown to better match the surrounding vegetation. A few species are brightly marked with bold stripes. Their bodies are usually smooth, but some vary from slightly to very rough. A few species are covered with short, sharp spines. The head is distinct. Compound eyes are present, with each eye having multiple lenses. There are no simple eyes, or eyes with a single lens. Their chewing mouthparts are directed forward. Stick insects may have fully developed or small wings or lack wings altogether, except for one species with small, rounded wings in southern Florida. All six legs are similar to one another in size and shape and are not designed for jumping. The fingerlike appendages on the tip of the abdomen are very short. Some males have claspers on the tips of their abdomens used to grasp the female while mating. Females have longer and heavier bodies than males.

Stick insects are mostly long, slender insects resembling twigs. They are sometimes two-toned, with lighter colors underneath and darker colors above. Some species have fully developed wings, while those of others are very small or absent altogether. Several stick insects have beautifully colored hind wings and rival the color of butterflies. Unlike grasshoppers, the back legs are not enlarged for jumping. Instead, all of their legs are about the same size and length. They range in length from 1.2 to 12.9 inches (30 to 328 millimeters). Several species of tropical phasmids are among the world's longest insects. For example, the body of Australia's Phobaeticus kirbyi reaches up to 12.9 inches (328 millimeters) in length, but with its front legs outstretched in front of its body, its total length jumps to 21.5 inches (546 millimeters).

Leaf insects have broad, flattened, leaflike bodies and legs. The wings are long and slender in males, shorter and wider in females, but they do not cover the edges of the abdomen. They measure 1.1 to 4.4 inches (28 to 112 millimeters) in length. The largest leaf insect is from Malaysia.

Timemas are not typical of stick or leaf insects. They are smaller (0.5 to 1.2 inches or 13 to 30 millimeters), somewhat flattened insects with thicker bodies and never have wings. Unlike most other phasmids, timemas are able to jump when threatened.

GEOGRAPHIC RANGE

Phasmids live on all continents, except Antarctica. They are also found on many islands. There are approximately three thousand species of phasmids worldwide, with about forty-four species in Canada and the United States.

HABITAT

Phasmids are found in a wide variety of habitats in warmer and tropical climates, including gardens, woodlands, pine and fir forests, chaparral, desert scrub, and grasslands. They are most common in moist, tropical forests. Phasmids spend their days resting on shrubs and trees or hiding in nearby leaf litter or crevices (KREH-vuh-ses).

DIET

Phasmids eat many different kinds of plants, chewing large, circular bites along the edges of leaves. A few species also eat bark and flowers. Most species eat a wide variety of plants, but a few are specialists and prefer feeding on only a few closely related species. Insect zoos and hobbyists, people that raise phasmids in captivity for fun, have successfully kept many tropical species on plants other than what they would normally eat in the wild. These plants include oak, pyracantha, bramble, Australian gum, and guava.

BEHAVIOR AND REPRODUCTION

Phasmids spend most of their time hidden among their food plants, remaining absolutely motionless. They become active at night to feed and locate mates. Stick insects are sometimes found perching on walls and window screens with their fore legs extended forward. Since most species are colored in various shades of greens and browns, camouflage and remaining still are their first lines of defense. Some species are able to change their colors to better match their backgrounds. Many pretend to be dead when threatened and fall to the ground, where they become lost among the leaves, grasses, and other vegetation. They might even voluntarily break off a leg to distract a predator (PREH-duh-ter) or animal that hunts other animals for food. Several species have bright, contrasting colors to warn predators that they will spray a foul-smelling, milky defensive fluid from glands in the thorax or midsection. This fluid can cause temporary blindness if it gets in the eyes. Winged species will suddenly open their colorful wings and begin to rattle them in an attempt to startle a potential predator.

Males transfer the sperm packet directly into the reproductive organs of the females during mating. After mating the male will remain clinging to the female for several hours or days. In fact, male timemas spend most of their adult lives riding around on the back of adult females. This behavior prevents other males from mating with her. If males are not available, some species of phasmids can reproduce by parthenogenesis (PAR-thuh-no-JEH-nuh-sihs). Parthenogenesis does not require sperm from a male to produce healthy eggs. All parthenogenetic eggs hatch into females. In a few species, males are completely unknown, and reproduction is entirely by parthenogenesis.

Females lay between one hundred and two thousand eggs. Some species drop or flick their eggs to the ground, while others glue them singly or in batches to leaves and branches. A few actually place them inside leaf tissues. Phasmid eggs are very distinctive in shape, size, and color. Seedlike eggs often have a caplike handle that makes it easy for ants to carry them back to their nests. This actually benefits the eggs by keeping them out of reach of other predators. The ants eat only the cap, leaving the rest of the egg intact.

Depending on the species, the eggs will hatch anywhere from about a month to more than a year. The larvae (LAR-vee), or young of the animal that must change form before they become adults, strongly resemble the adults but lack wings (if present) and are not able to reproduce. Phasmid larvae usually molt, or shed their exoskeleton or hard outer covering, six to seven times and can replace lost or damaged limbs as they grow. Adults may live for several months, although some species may live up to three years.

STICK INSECTS AND PEOPLE

Natives of Goodenough Island, New Guinea, used the large hooks found on the back legs of male Eurycantha, a large spiny species common in the region, as fishhooks. Large and spectacularly colored species are commonly collected, preserved, and mounted in decorative frames for sale to tourists. Living phasmids are popular with hobbyists, but the importation of exotic stick insects is strictly regulated in many countries, especially in the United States. Authorities are concerned that the accidentally or purposefully introduced foreign species may become plant pests. Exotic species can also crowd out native species or introduce harmful diseases to their populations. Exotic species are often displayed, under special permits, in insect zoos and other institutions with living arthropod exhibits. Nearly all phasmids are harmless, but some species can deliver a painful pinch with sharp spines on their legs or squirt bad-smelling sprays that are known to cause temporary blindness in humans. A few stick insects are occasionally regarded as pests when they devour nearly all of the leaves of individual trees.

A TALE OF PHASMID FAKERY

Many species of insects mimic ants, and with good reason. Ants are well known for their defensive behaviors. Many predators avoid them because they will not hesitate to bite, sting, or spray stinging chemicals at their attackers. The young larvae of some stick insects are thought to mimic the movement of ants by running frantically over the ground.

CONSERVATION STATUS

Only one species of phasmid is listed by the World Conservation Union (IUCN). The Australian Lord Howe Island stick insect, sometimes called the "land lobster," is listed as Critically Endangered, or facing an extremely high risk of extinction in the wild. It was thought that they had been wiped out, pushed to extinction by introduction of insect-eating rats to the island in 1918. Fortunately, a living population of this spectacular insect was discovered in 2001 on Balls Pyramid, a rugged and bare volcanic rock formation. The Australian authorities are now trying to breed them in the laboratory for later release back into rat-free habitats.

Insect zoos and hobbyists rely mainly on phasmids reared from captive stock and not specimens caught in the wild. However, some large and showy species, such as the jungle nymph from the Cameron Highlands of Malaysia, are sometimes collected in large numbers in the wild and exported around the world.

JUNGLE NYMPH (Heteropteryx dilatata): SPECIES ACCOUNTS

Physical characteristics: The large, broad, spiny, apple green females measure 5.4 to 6.3 inches (140 to 160 millimeters) in length and weigh up to 2.3 ounces (65 grams). The short green forewings of the adult completely cover the hind wings underneath. Males are smaller, ranging in length from 3.1 to 3.5 inches (80 to 90 millimeters) and are mottled brown with slender wings that cover the entire length of the abdomen. The legs of both males and females are very spiny.

Geographic range: The jungle nymph is found in Java, Malaysia, Sarawak, Singapore, Sumatra, and Thailand.

Habitat: The jungle nymph lives on shrubs and trees in tropical forests.

Diet: This species eats the leaves of many kinds of bushes and trees in the wild and in captivity, including eugenia, guava, and bramble.

Behavior and reproduction: When threatened both males and females arch their bodies forward and strike out with their spiny hind legs. They also produce a hissing sound by rubbing their forewings and hind wings together. They will also bite if none of the previous strategies work. Gynandromorphs (GAI-nan-druh-morfs), individuals that show the characteristics of both males and females, are sometimes found in the wild and in captive-bred colonies.

Females bury their eggs in soil. The eggs take eight to eighteen months to hatch.

Jungle nymphs and people: The droppings of jungle nymphs are dried and mixed with herbs in China as a cure for numerous ailments, such as asthma. Chinese families often rear them on guava leaves to keep a steady supply of droppings handy. This is also a popular species for live displays in zoos and butterfly houses around the world.

Conservation status: This species is not endangered or threatened. However, specimens are routinely collected in large numbers, mounted and framed, and sold to tourists. ∎

INDIAN STICK INSECT (Carausius morosus): SPECIES ACCOUNTS

Physical characteristics: This species is somewhat smooth, plain, wingless, with antennae about one-third the length of the body. Adult males are thin, brown, and reach 1.9 to 2.4 inches (48 to 61 millimeters) in length. The bodies of the females are somewhat knobby and measure 2.8 to 3.3 inches (70 to 84 millimeters) in length. They are variously colored dull green or brown. The inner base of each foreleg is bright red.

Geographic range: Indian stick insects are native to Shembagonor and Trichinopoly in Madura Province, southern India. They now also live in Madagascar and the Cape Town suburbs of South Africa. Released individuals and escapes are occasionally found in the United States, United Kingdom, and other countries of Europe. In these cooler climates they generally die out within a few years.

Habitat: These insects live on many species of bushes and trees in India. In other parts of the world they are found on garden plants and natural vegetation.

Diet: This species eats a wide variety of plants in the wild and in captivity. Captive colonies are often kept on hedges.

Behavior and reproduction: Indian stick insects play dead when disturbed and will remain motionless for hours.

Males are rare, and reproduction is mainly by parthenogenesis. Females drop several hundred eggs to the ground. The life cycle usually is completed in twelve to sixteen months. Gynandromorphs also are reared occasionally.

Indian stick insects and people: This species is very easy to raise and is regularly used as a study animal by scientists.

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

COMMON AMERICAN WALKINGSTICK (Diapheromera femorata): SPECIES ACCOUNTS

Physical characteristics: This species is long, slender, and shiny, with long antennae. Males measure 2.2 to 3.3 inches (55 to 84 millimeters) in length. The females are 2.8 to 4.0 inches (70 to 101 millimeters) long. The middle legs of the male are banded, and the appendages on the tip of their abdomen are distinctive and curved. Adult females are green, gray, or brown, and males are brownish with stripes.

Geographic range: The common American walkingstick is found in North America, from southern Canada, from Manitoba to Quebec, south to Arizona and Florida, and also in northern Mexico.

Habitat: This species is found in woodlands populated with broadleaf trees.

Diet: The adults prefer eating oak leaves, while the larvae will also feed on various plants and shrubs under the oaks.

Behavior and reproduction: The common American walkingstick relies on its camouflage to hide among vegetation. Eggs are dropped to the ground in fall and hatch in spring.

Common American walkingsticks and people: This species is sometimes regarded as a pest when large numbers eat most of the leaves on a tree.

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

MACLEAY'S SPECTRE (Extatosoma tiaratum): SPECIES ACCOUNTS

Physical characteristics: Macleay's spectre is a large, winged leaf-mimic. The plump, heavy females have short wings and weigh 0.7 to 1.1 ounces (20 to 30 grams) and measure 3.9 to 6.3 inches (100 to 160 mm) in length. The smaller, lighter males have fully developed wings covering the length of the abdomen and range from 3.2 to 4.5 inches (81 to 115 millimeters). The legs and bodies of both males and females have leaflike expansions. Females are brown, sometimes green, and very spiny.

Geographic range: They are found in parts of New South Wales and southeast and north Queensland, Australia.

Habitat: This species is found in suitable bush or gardens.

Diet: Their natural food plants include eucalyptus, but they will also accept oak and pyracantha in captivity.

Behavior and reproduction: In response to a perceived threat, the spiny hind legs are spread and strike out. Forelegs are waved, and sometimes the body sways from side to side. Females curl their abdomens up over the rest of their bodies, a posture suggesting that of a scorpion.

It is possible that females attract males by flashes of ultraviolet light. Reproduction is usually by mating, but females are capable of reproducing by parthenogenesis. Adults live for several months. Females lay several hundred eggs, which are flicked to the ground. The eggs take five to eight months to hatch. The larvae take anywhere from three to six months to reach adulthood.

Macleay's spectres and people: This species is popular as a display animal in insect zoos worldwide. In parts of Papua, New Guinea, one of its relatives is sometimes cooked and eaten by local people.

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

JAVAN LEAF INSECT (Phyllium bioculatum): SPECIES ACCOUNTS

Physical characteristics: The Javan leaf insect is a supreme leaf-mimic. Their broad green bodies and legs, with or without spots, are quite flattened. The antennae of the females are very short, while those of the male are longer. Adult males are 1.8 to 2.7 inches (46 to 68 millimeters) in length. Females range from 2.6 to 3.7 inches (67 to 94 millimeters).

Geographic range: This species is widespread in Southeast Asia, including Borneo, China, India, Java, Malaysia, Singapore, and Sumatra. They are also found in Madagascar, Mauritius, and the Seychelles.

Habitat: They live on tropical rainforest vegetation.

Diet: Javan leaf insects eat the leaves of guava and rambutan. In captivity they will also eat oak and bramble.

Behavior and reproduction: Males can fly well and are usually short-lived, while the longer-lived females are flightless. Both males and females rely on their excellent camouflage to avoid predators.

Females drop their oddly shaped, seedlike eggs to the ground. The larvae may take several months to reach adulthood.

Javan leaf insects and people: This species is popular with hobbyists and as a display animal in insect zoos, although they can sometimes be difficult to maintain.

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

FOR MORE INFORMATION

Books:

Brock, P. D. The Amazing World of Stick and Leaf Insects. Orpington, U.K.: Amateur Entomologists' Society, 1999.

Brock, P. D. A Complete Guide to Breeding Stick and Leaf Insects. Havant, U.K.: T.F.H. Kingdom Books, 2000.

Brock, P. D. Stick and Leaf Insects of Peninsular Malaysia and Singapore. Kuala Lumpur: Malaysian Nature Society, 1999.

Periodicals:

Sivinski, J. "When Is a Stick Not a Stick?" Natural History no. 1012 (June 1992): 30–35.

Vallés, S. R. "Phasmids." Reptilia no. 13 (October 2000): 16–25.

Web sites:

Gordon's Phasmida Page.http://www.earthlife.net/insects/phasmida.html (accessed on September 26, 2004).

Phasmatodea.http://www.cals.ncsu.edu:8050/course/ent425/compendium/stick.html (accessed on September 26, 2004).

"Phasmatodea. Stick Insects, Leaf Insects." Ecowatch.http://www.ento.csiro.au/Ecowatch/Insects_Invertebrates/phasmatodea.htm (accessed September on 26, 2004).