Phasmida

(Stick and leaf insects)

Class Insecta

Order Phasmida

Number of families 8

Evolution and systematics

The oldest fossil specimens of Phasmida date to the Triassic period—as long ago as 225 million years. Relatively few fossil species have been found, and they include doubtful records. Occasionally a puzzle to entomologists, the Phasmida (whose name derives from a Greek word meaning "apparition") comprise stick and leaf insects, generally accepted as orthopteroid insects. Other alternatives have been proposed, however. There are about 3,000 species of phasmids, although in this understudied order this number probably includes about 30% as yet unidentified synonyms (repeated descriptions). Numerous species still await formal description.

Extant species usually are divided into eight families, though some researchers cite just two, based on a reluctance to accept Bradley and Galil's 1977 rearrangement of the order. There are three suborders, the Anareolatae, Areolatae, and Timematodea. The Areolatae has five families, thought to be distinguished from the Anareolatae by the presence of a sunken area on the underside of the mid-tibia and hind tibia, but this is not always a reliable feature. The families include the Phylliidae (4 genera, 36 known species), Aschiphasmatidae (18 genera, c. 100 species), Bacillidae (48 genera, c. 230 species), Heteronemiidae (1 genus, 2 species), and Pseudophasmatidae (51 genera, c. 300 species). Two large families, the Diapheromeridae (180 genera, c. 1,600 species) and the Phasmatidae (100 genera, c. 700 species), represent the Anareolatae. The Timematodea has only one family, the Timematidae (1 genus, 21 species). These small stick insects are not typical phasmids, having the ability to jump, unlike almost all other species in the order. It is questionable whether they are indeed phasmids, and phylogenetic research is not conclusive. Studies relating to phylogeny are scarce and limited in scope. The eggs of each phasmid are distinctive and are important in classification of these insects.

Physical characteristics

Stick insects range in length from Timema cristinae at 0.46 in (11.6 mm) to Phobaeticus kirbyi at 12.9 in (328 mm), or 21.5 in (546 mm) with legs outstretched. Numerous phasmid "giants" easily rank as the world's longest insects. The largest leaf insect is Phyllium (Pulchriphyllium) giganteum from Malaysia, at 4.4 in (113 mm), while the smallest is Nanophyllium pygmaeum, at only 1.1 in (28 mm).

The elongate stick insects typically resemble twigs, and leaf insects (Phylliidae) look like broadened, flat leaves, providing one of the best camouflages in the animal world. Phasmids are smooth, scarcely or heavily granulated, and sometimes with extensive spines and tubercles. The legs are similar to one another. Cerci usually are short. Females often are larger than the typically very thin males. Wings are present in many species, but they may be shortened or even absent. While they

frequently are green or brown to better match vegetation, phasmids sometimes are brightly colored or boldly striped. Species with colorful hind wings rank among the most spectacular of all insects.

Most stick insects belong to the Diapheromeridae and Phasmatidae. The Diapheromeridae are a mixture of winged and wingless species, while the Phasmatidae include the world's longest insects as well as more bulky, often winged, insects. The Asian Aschiphasmatidae are mainly winged, although the forewings are usually only a stalk-like structure. The Bacillidae includes spectacular, broad-bodied species. The Neotropical Pseudophasmatidae have many beautiful winged species to rival Asian winged representatives of the Diapheromeridae. The Heteronemiidae has recently been reduced to only a single wingless genus. The leaf insects (Phylliidae) are mainly from Southeast Asia, although some have successfully spread elsewhere.

Distribution

Phasmids are mostly tropical and subtropical throughout the world, although some hardy species persist in temperate areas. There even are three species of stick insects well established in the United Kingdom. Pet keepers occasionally deliberately discard stocks in the wild, and there also are accidental releases. Tropical species do not normally survive long in the United Kingdom, but escapees can become established in warmer climates.

Habitat

Found in a variety of habitats, phasmids can be abundant in wet and dry forests and in grasslands. In some countries they are common in gardens. Although they sometimes are found resting on or near their food plants in the daytime, they often are well hidden under leaves on the forest floor or in crevices. Tropical forests teem with these insects at night, when they move from their hiding places under cover of darkness. Some species frequent treetops and hence are seen rarely.

Behavior

Mostly nocturnal and remaining motionless in the daytime, phasmids blend in with the background; hence procrypsis (concealment from predators) is the primary defense. Some species even have the ability to change color to match their surroundings better, perhaps becoming a darker shade toward nighttime. Two-tone species with darker undersides are not uncommon. Many species feign death when disturbed, falling to the ground and remaining motionless; they may willingly shed a limb ("autotomy") in an effort to escape. The nymphs of some species (Extatosoma tiaratum) are thought to mimic ants. Many winged species flash open brightly colored wings or rustle their wings to startle predators; others fly away and "vanish" suddenly within vegetation. Some species, such as the Eurycnema from Australasia, use spines on their legs to strike out in attack. Certain stick insects, such as Anisomorpha

buprestoides from the southeastern United States, exhibit warning colors on their bodies, perhaps stripes, and eject foulsmelling fluid from glands on the upper part of the thorax or from their mouthparts.

Feeding ecology and diet

Phasmids feed on leaves, taking large, circular bites out of the edges. A few species also eat flowers or bark. Some species have very few host plants, whereas many others accept the leaves of numerous different plants. It therefore is not surprising that pet keepers in different parts of the world often successfully rear phasmids in captivity on Eucalyptus, Psidium, Rubus, and Quercus species, regardless of their natural host plants.

Reproductive biology

Although they usually reproduce bisexually, many phasmids are able to reproduce parthenogenetically if males are absent, producing all-female offspring and thus enabling the species to survive. Only females are known in some species. Where males occur, mating typically involves the transfer of a spermatophore (sperm sac) from the male to the female. Hybridization has been reported in Bacillus species from Europe. Between 100 and 2,000 eggs per species are either dropped or flicked to the ground; glued to surfaces, such as leaves, singly or in batches; or pierced into leaves. The eggs of many phasmids have a caplike structure, or operculum, on top, which assists ants in transferring the eggs to their underground nests. This benefits phasmids, since the ants eat only the caps, leaving the egg capsules to hatch later rather than being eaten on the forest floor. Nymphs hatch after a month to more than a year, depending on species, and frequently look rather like a miniature version of the adult. They can regrow lost limbs at the next nymphal molt. Nymphs typically molt six to seven times. Adults often live for several months and up to three years in a few species. In some genera, such as Timema in western North America, adult males mount females and remain there throughout their life span, in an effort to prevent the females from mating with rival males.

Conservation status

Many phasmids are known only from the originally described specimen(s), and their status is not known. The pet trade relies mainly on insects reared from captive stock. Showy species sometimes are imported in great numbers from

the wild, however, as with Heteropteryx dilatata from the Cameron Highlands of Malaysia. Trade declined by the early twenty-first century, although they still are collected widely for use in the framing industry. The spectacular Lord Howe Island (Australia) stick insect, Dryococelus australis (listed as Endangered by the IUCN), was thought to have become extinct following the introduction of rats to the island in 1918. The rediscovery of this species on a rugged and barren volcanic spire known as Balls Pyramid in 2001 caused great excitement. A captive-breeding project is under way by Australian authorities. The import of stick insects is regulated strictly in many countries, including the United States, as the insects may become pests.

Significance to humans

There are few reports of phasmids being eaten by humans. An old report states that natives of Goodenough Island, New Guinea, used the boldly spined hind legs of a Eurycantha species as fishhooks. The spectacular appearance of phasmids has led to their commercial use for framing (like butterflies, they are sold mainly to tourists as home decorations), in films, and on T-shirts, postcards, and toys. Phasmids are showy and relatively easy to look after, making them very popular insects in the pet trade. Nearly all species are harmless, but some need to be handled carefully, since they have shown aggressive defensive behavior. In extreme cases a few species squirt defensive sprays that have been known to cause temporary blindness in humans. Certain species are regarded as pests, with occasional population explosions resulting in severe defoliation of plants.

Species accounts

List of Species

Mediterranean stick insect

Bacillus rossius

family

Bacillidae

taxonomy

Bacillus rossius Rossi, 1788, Pisa (Tuscany), Italy.

other common names

English: Corsican stick insect.

physical characteristics

Rather plain, wingless, elongate species with short antennae. The male is 2.0–3.1 in (52–79 mm) long; the female is 2.5–4.1 in (64–105 mm) long. Females are green or brown, and the much thinner males are brown.

distribution

Widespread throughout the warmer parts of Europe and the Mediterranean countries.

habitat

Found where bushes grow that support their food plants but prefers coastal areas.

behavior

Nymphs and adults sometimes sway in the breeze to imitate moving twigs.

feeding ecology and diet

Widespread on bramble Rubus fruticosus and many species in the rose family (Rosaceae).

reproductive biology

Adults are most common around August and September, although they can be seen all year in some areas. Each female lays about 1,000 eggs, which are dropped to the ground. The resulting nymphs hatch in three to eight months (some over winter), and nymphs mature in two to four months. Adults live several months.

conservation status

Not threatened.

significance to humans

None known.

Jungle nymph

Heteropteryx dilatata

family

Bacillidae

taxonomy

Phasma dilatatum Parkinson, 1798, Asia.

other common names

None known.

physical characteristics

Apple green females with large green forewings; hind wings are hidden beneath the forewings. Males are mottled brown with large wings. Males are 3.1–3.5 in (80–90 mm) long, and females are 5.4–6.3 in (140–160 mm) long. Females are very broadened and heavy, up to 2.3 oz (65 g). Both sexes with spiny legs.

distribution

Java, Malaysia, Sarawak, Singapore, Sumatra, Thailand.

habitat

Lives in rainforest.

behavior

Females are camouflaged with a darker green underside. If disturbed, both sexes react, such as by arching the body forward and striking out with the spiny hind legs. A hissing sound is produced by rubbing the forewings and hind wings together. Biting is a last resort. Gynandromorphs (part male, part female) occasionally are reared or found in the wild.

feeding ecology and diet

Eats leaves of several bushes and trees, including Eugenia, Grewia, Psidium, Rubus, and Uncaria. Also feeds widely in captivity.

reproductive biology

The life cycle is long. Females bury eggs in soil, and they take eight to 18 months to hatch.

conservation status

Not threatened at present but heavily collected for use in the framing industry or for the pet trade.

significance to humans

Droppings of these phasmids, dried and mixed with herbs, are said to cure numerous ailments, such as asthma. Chinese families therefore often rear them on guava leaves, from which the medicinal properties are thought to derive. This is a popular species for live displays in zoos and butterfly houses worldwide.

Thunberg's stick insect

Macynia labiata

family

Bacillidae

taxonomy

Mantis labiata Thunberg, 1784. Type locality not recorded but probably Cape Town, South Africa.

other common names

English: Green stick insect

physical characteristics

The female is small and plump. The male is typically sticklike, with long cerci (claspers). Both sexes have short antennae. Male grow to 1.6–2 in (42–52 mm) and females to 2.1–2.2 in (54–56 mm). Head and pronotum are yellowish with green bands. Females usually are green and sometimes pink.

distribution

Cape Province, particularly around Cape Town, South Africa

habitat

Lives on natural fynbos vegetation.

behavior

A master of camouflage. If disturbed, males sometimes walk away quickly.

feeding ecology and diet

Heathers and several plants associated with fynbos.

reproductive biology

Females mate frequently, with different males. Adults are most common between September and January, although they can be found throughout the year. Adults live a few months, with females laying eggs that hatch after several months.

conservation status

Not threatened.

significance to humans

None known.

Indian stick insect

Carausius morosus

family

Diapheromeridae

taxonomy

Dixippus morosus Sinéty, 1901, Palni Hills, Tamil Nadu, southern India.

other common names

English: Laboratory stick insect.

physical characteristics

Plain, wingless species with medium-size antennae. Males grow to 1.9–2.4 in (48–61 mm) and females to 2.8–3.3 in (70–84 mm). Females are various shades of dull green or brown, with some small tubercles (knobs); they are brightened up by a vivid red inner base of the foreleg. The much thinner males are brown.

distribution

Shembagonor and Trichinopoly in Madura Province, southern India. An established alien in Madagascar; the Cape Town suburbs, South Africa; and California, United States, they also are seen occasionally in Europe, including the United Kingdom, usually as a result of discarded cultures. In temperate climates they generally die out within a few years.

habitat

Lives on unnamed bushes and trees in India. Elsewhere found in gardens and natural vegetation on ivy and many other plants.

behavior

A classic "stick" insect, which plays dead and can remain motionless for hours. Mainly parthenogenetic, males rarely are seen in captivity. When they do occur, they are believed to be genetic females with male characteristics and are sterile. Gynandromorphs (with part male and part female characteristics) also are reared occasionally. Males were present in the original culture but soon died out.

feeding ecology and diet

In captivity it accepts a vast range of plants but often is kept on privet Ligustrum species, often used as garden hedges in northern Europe.

reproductive biology

Females drop several hundred eggs to the ground. The life cycle usually is completed in 12–16 months.

conservation status

Not threatened.

significance to humans

The most written-about phasmid, frequently used in experiments as well as one of the most widely cultured insects. This hardy, prolific species is a wonderful introduction to the insect world for schoolchildren.

Common American walkingstick

Diapheromera femorata

family

Diapheromeridae

taxonomy

Spectrum femoratum Say, 1824, Niagara Falls, United States.

other common names

English: Walkingstick.

physical characteristics

Long and slender, with long antennae. Males reach 2.2–3.3 in (55–84 mm) in length and females 2.8–4.0 in (70–101 mm). The hind femur has an apical spine. Midlegs of the male are banded, and the cerci are large and curved inward. Adult females are green, gray, or brown, and males are brownish with stripes. Both sexes are glossy.

distribution

Canada (Manitoba to Quebec) and distributed widely in the United States, south to Arizona and Florida.

habitat

Forests.

behavior

Relies on its camouflage among vegetation.

feeding ecology and diet

Prefers oaks (Quercus species), though nymphs may feed on the lower vegetation of various plants.

reproductive biology

Adults are most common in August and September, dropping 100–150 eggs to the ground. These overwinter and hatch in June or July of the next year.

conservation status

Not threatened.

significance to humans

Sometimes regarded as a pest, this species can cause severe defoliation of host trees.

Darwin stick insect

Eurycnema osiris

family

Phasmatidae

taxonomy

Phasma (Diura) osiris Gray, 1834, Melville Island, Australia.

other common names

None known.

physical characteristics

Large, spectacular, green-winged species. Males reach 4.5–5.3 in (115–134 mm), and females grow to 6.9–8.7 in (170–221 mm). The female's thorax has a bold pink central stripe. Legs are spiny.

distribution

Found in northern Australia (Northern Territory, Queensland, and Western Australia).

habitat

Lives in suitable bush, often high up in trees.

behavior

Typically well camouflaged in vegetation, but if disturbed they resort to a startle display, showing the bright red underside of the wings. The spiny hind legs are spread and strike out.

feeding ecology and diet

Prefers Acacia and Eucalyptus species.

reproductive biology

Adults are most common May to August but have been reported throughout the year. They live for several months, laying a few hundred eggs, which take several months to hatch.

conservation status

Not threatened.

significance to humans

None known.

Macleay's spectre

Extatosoma tiaratum tiaratum

family

Phasmatidae

taxonomy

Phasma tiaratum tiaratum Macleay, 1826, probably Parramatta, New South Wales, Australia.

other common names

English: Giant prickly stick insect.

physical characteristics

Large and spectacular winged species, though wings are rudimentary in the plump, heavy females (0.7–1.1 oz, or 20–30 g). Males reach 3.2–4.5 in (81–115 mm); females reach 3.9–6.3 in (100–160 mm). A leaf mimic. Legs and bodies of both sexes have leaflike expansions. Females are very spiny and brown or sometimes green. The subspecies Extatosoma tiaratum bufonium is a lichen mimic.

distribution

Parts of New South Wales and southeast and north Queens-land, Australia.

habitat

Found in suitable bush or gardens. Extatosoma tiaratum bufonium usually is found at higher altitudes.

behavior

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, resembling scorpions. Defense glands release a chemical.

feeding ecology and diet

Eucalyptus species are included among their natural food plants.

reproductive biology

It is possible that females attract males by flashes of ultraviolet light. Usually reproducing bisexually, females sometimes can reproduce parthenogenetically. 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, and nymphs mature in three to six months.

conservation status

Not threatened.

significance to humans

Popular in zoos worldwide. In parts of Papua New Guinea, its relative Extatosoma popa popa sometimes is cooked and eaten by natives.

Coconut stick insect

Graeffea crouanii

family

Phasmatidae

taxonomy

Bacillus crouanii Le Guillou, 1841, Samoa Island.

other common names

None known.

physical characteristics

Broad green or pinkish-brown species, with bold pink, shortened wings. Males grow to 2.6–2.8 in (65–70 mm) and females to 4.1–4.6 in (105–116 mm).

distribution

South Pacific Islands.

habitat

Found wherever coconut palms grow.

behavior

Well camouflaged on or near coconut palms, where they typically lay flat underneath leaflets. When disturbed, they may display their bright pink wings.

feeding ecology and diet

Feeds mainly on coconut palms (Cocos nucifera), devouring the green tissue of leaflets and sometimes the youngest fronds.

reproductive biology

Females lay a few hundred eggs, which hatch in about three to four months.

conservation status

Not threatened.

significance to humans

When population explosions of this species occur, they can result in defoliation of coconut palms, leading to serious losses to planters and village communities.

Javan leaf insect

Phyllium (Pulchriphyllium) bioculatum

family

Phylliidae

taxonomy

Phyllium bioculatum Gray, 1832. Type locality not recorded but probably Southeast Asia or the Seychelles.

other common names

English: Gray's leaf insect.

physical characteristics

Rather flattened, with a broad body and legs. Color varies but often is green with or without mottling. Some variability in body shape, causing confusion among taxonomists. Females have very short antennae; those of the male are longer. Males grow to 1.8–12.7 in (46–68 mm) and females to 2.6–3.7 in (67–94 mm).

distribution

Widespread in Southeast Asia, in Borneo, China, India, Java, Malaysia, Singapore, and Sumatra. Also found in Madagascar, Mauritius, and the Seychelles.

habitat

Lives in rainforest.

behavior

Relies on its excellent camouflage.

feeding ecology and diet

Food plants include Nephelium lappaceum and Psidium guajava. In captivity some accept Quercus and Rubus species.

reproductive biology

The strangely shaped, large, seedlike eggs are dropped to the ground. Nymphs take several months to mature. Males can fly well and often are short-lived.

conservation status

Not threatened.

significance to humans

None known.

Resources

Books

Bragg, Philip E. Phasmids of Borneo. Kota Kinabalu, Borneo: Natural History Publications, 2001.

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

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

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

Grösser, Detlef. Wandelnde Blätter. (Book on Leaf Insects). Frankfurt, Germany: Edition Chimaira, 2001.

Otte, Daniel, and Paul Brock. Phasmida Species File: A Catalog of the Stick and Leaf Insects of the World. Philadelphia: Orthopterists' Society, 2003.

Periodicals

Bedford, Geoffrey O. "Biology and Ecology of the Phasmatodea." Annual Review of Entomology 23 (1978): 125–149.

Bradley, James Chester, and Bella S. Galil. "The Taxonomic Arrangement of the Phasmatodea with Keys to the Subfamilies and Tribes." Proceedings of the Entomological Society of Washington 79, no. 2 (1977): 176–208.

Brock, Paul D. "Studies on the Stick-Insect Genus Eurycnema Audinet-Serville (Phasmida: Phasmatidae) with Particular Reference to Australian Species." Journal of Orthoptera Research 7 (December 1998): 61–70.

——. "Studies of the Australian Stick-Insect Genus Extatosoma (Phasmida: Phasmatidae: Tropoderinae: Extatosomatini)." Journal of Orthoptera Research 10, part 2 (2002): 303–313.

Clark, J. T. "A Key to the Eggs of Stick and Leaf Insects (Phasmida)." Systematic Entomology 4, no. 4 (1979): 325–331.

Zompro, O. "A Generic Revision of the Insect Order Phasmatodea: The New World Genera of the Stick-Insect Family Diapheromeridae. Diapheromeridae = Heteronemiidae: Hemeronemiinae sensu Bradley & Galil (1977)." Review Suisse de Zoologie 108, no. 1 (2001): 189–255.

Organizations

The Phasmid Study Group. 40 Thorndike Road, Slough, Berkshire SL2 1SR United Kingdom. Phone: 01753 579447.

Paul D. Brock