The Phasmatodea (also known as Phasmida, Phasmatoptera or Spectra) are an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...

s whose members are variously known as stick insects, stick-bugs, walking sticks, stick animals, or bug sticks. They are also occasionally referred to as Devil's darning needles, although this name is shared by both

dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threa ...

and crane flies. They can be generally referred to as phasmatodeans, phasmids, or ghost insects, with phasmids in the family Phylliidae called leaf insects, leaf-bugs, walking leaves, or bug leaves. The group's name is derived from the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...

', meaning an apparition or

phantom Phantom may refer to: * Spirit (animating force), the vital principle or animating force within all living things ** Ghost, the soul or spirit of a dead person or animal that can appear to the living Aircraft * Boeing Phantom Ray, a stealthy unm ...

, referring to their resemblance to vegetation while in fact being animals. Their natural

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

makes them difficult for predators to detect; still, many species have one of several secondary lines of defense in the form of startle displays, spines or toxic secretions. Stick insects from the genera '' Phryganistria'', '' Ctenomorpha'', and '' Phobaeticus'' include the world's longest insects. Members of the order are found on all continents except

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

, but they are most abundant in the

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...

and

subtropics The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° nort ...

. They are herbivorous, with many species living unobtrusively in the tree canopy. They have an

incomplete metamorphosis Hemimetabolism or hemimetaboly, also called incomplete metamorphosis and paurometabolism,McGavin, George C. ''Essential Entomology: An Order-by-Order Introduction''. Oxford: Oxford University Press, 2001. pp. 20. is the mode of development of certa ...

life cycle with three stages: egg,

nymph A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ...

and adult. Many phasmids are

parthenogenic Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

, and do not require fertilized eggs for female offspring to be produced. In hotter climates, they may breed all year round; in more temperate regions, the females lay eggs in the autumn before dying, and the new generation hatches in the spring. Some species have wings and can disperse by flying, while others are more restricted.

Description

Phasmids can be relatively large, ranging from to over in length. Females of the genus '' Phryganistria'' are the world's longest insects, measuring up to in total length in the case of an undescribed species, including the outstretched legs. The heaviest species of phasmid is likely to be '' Heteropteryx dilatata'', the females of which may weigh as much as . Some phasmids have cylindrical stick-like shapes, while others have flattened, leaflike shapes. Many species are wingless, or have reduced wings. The

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the c ...

is long in the winged species, since it houses the flight muscles, and is typically much shorter in the wingless forms. Where present, the first pair of wings is narrow and cornified (hardened), while the hind wings are broad, with straight veins along their length and multiple cross-veins. Their wing venation is unique among insects. The body is often further modified to resemble vegetation, with ridges resembling leaf veins, bark-like

tubercles In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection, ...

, and other forms of

. A few species, such as ''

Carausius morosus ''Carausius morosus'' (the 'common', 'Indian' or 'laboratory' stick insect) is a species of Phasmatodea (phasmid) often kept as pets by schools and individuals. Culture stocks originate from a collection from Tamil Nadu, India. Like the majorit ...

'', are even able to change their pigmentation to match their surroundings. The

mouthparts Mouthparts may refer to: * The parts of a mouth ** Arthropod mouthparts The mouthparts of arthropods have evolved into a number of forms, each adapted to a different style or mode of feeding. Most mouthparts represent modified, paired append ...

project out from the head. Chewing mandibles are uniform across species. The legs are typically long and slender, and some species are capable of limb

autotomy Autotomy (from the Greek ''auto-'', "self-" and ''tome'', "severing", αὐτοτομία) or self-amputation, is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude ...

(appendage shedding). Phasmids have long, slender antennae, as long as or longer than the rest of the body in some species. Australian Leaf Insect, portrait

All phasmids possess

compound eye A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which disti ...

s, but

ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

(light-sensitive organs) are only known from the five groups Lanceocercata, Necrosciinae, Pseudophasmatidae, Palophidae and Phylliidae. Of these only the first three groups have females with ocelli, which like the wings seems to have re-evolved from ancestors that had lost them. Phasmids have an impressive visual system that allows them to perceive significant detail even in dim conditions, which suits their typically

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

lifestyle. They are born equipped with tiny compound eyes with a limited number of facets. As phasmids grow through successive molts, the number of facets in each eye is increased along with the number of

photoreceptor cell A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiat ...

s. The sensitivity of the adult eye is at least tenfold that of the nymph in its first

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

(developmental stage). As the eye grows more complex, the mechanisms to adapt to dark/light changes are also enhanced: eyes in dark conditions evidence fewer screening pigments, which would block light, than during the daytime, and changes in the width of the retinal layer to adapt to changes in available light are significantly more pronounced in adults. The larger size of the adult insects' eyes makes them more prone to radiation damage. This explains why fully grown individuals are mostly nocturnal. Lessened sensitivity to light in the newly emerged insects helps them to escape from the

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constituent ...

wherein they are hatched and move upward into the more brightly illuminated foliage. Young stick insects are diurnal (daytime) feeders and move around freely, expanding their

foraging Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavi ...

range. Stick insects have two types of pads on their legs: sticky "toe pads" and non-stick "heel pads" a little further up their legs. The heel pads are covered in microscopic hairs which create strong friction at low pressure, enabling them to grip without having to be peeled energetically from the surface at each step. The sticky toe pads are used to provide additional grip when climbing but are not used on a level surface.

Distribution

Phasmatodea can be found all over the world except for the Antarctic and Patagonia. They are most numerous in the

and

. The greatest diversity is found in

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

, followed by

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

, Central America, and the southern United States. Over 300 species are known from the island of

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and e ...

, making it the richest place in the world for Phasmatodea.

Antipredator adaptations

Phasmatodea species exhibit mechanisms for defense from predators that prevent an attack from happening in the first place (primary defense), and defenses that are deployed after an attack has been initiated (secondary defense). The defense mechanism most readily identifiable with Phasmatodea is

, in the form of a plant

mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry f ...

. Most phasmids are known for effectively replicating the forms of sticks and leaves, and the bodies of some species (such as '' Pseudodiacantha macklotti'' and ''

Bactrododema centaurum ''Bactrododema'' is a genus of the stick insect family Diapheromeridae. Species of this genus have a relictual distribution and are endemic to southern Africa Southern Africa is the southernmost subregion of the African continent, south ...

'') are covered in mossy or

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.Bostra scabrinota'', '' Timema californica''). In a further behavioral adaptation to supplement

crypsis In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean lifestyle an ...

, a number of species perform a rocking motion where the body is swayed from side to side; this is thought to mimic the movement of leaves or twigs swaying in the breeze. Another method by which stick insects avoid predation and resemble twigs is by entering a cataleptic state, where the insect adopts a rigid, motionless posture that can be maintained for a long period. The nocturnal feeding habits of adults also help Phasmatodea to remain concealed from predators. Flügel Peruphasma schultei

Haaniella dehaanii-subadult threaten female

In a seemingly different method of defense, many species of Phasmatodea seek to startle the encroaching predator by flashing bright colors that are normally hidden, and making a loud noise. When disturbed on a branch or foliage, some species, while dropping to the undergrowth to escape, will open their wings momentarily during free fall to display bright colors that disappear when the insect lands. Others will maintain their display for up to 20 minutes, hoping to frighten the predator and convey the appearance of a larger size. Some, such as '' Pterinoxylus spinulosus'', accompany the visual display with the noise made by rubbing together parts of the wings. Some species, such as the young nymphs of ''

Extatosoma tiaratum ''Extatosoma tiaratum'', commonly known as the spiny leaf insect, the giant prickly stick insect, Macleay's spectre, or the Australian walking stick, is a large species of Australian stick insect endemic to Australia. The species has the Phasmi ...

'', have been observed to curl the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...

upwards over the body and head to resemble ants or scorpions in an act of

, another defense mechanism by which the insects avoid becoming prey. The eggs of some species such as '' Diapheromera femorata'' have fleshy projections resembling elaiosomes (fleshy structures sometimes attached to seeds) that attract ants. When the egg has been carried to the colony, the adult ant feeds the elaiosome to a larva while the phasmid egg is left to develop in the recesses of the nest in a protected environment. When threatened, some phasmids that are equipped with femoral spines on the metathoracic legs ('' Oncotophasma martini'', ''

Eurycantha calcarata ''Eurycantha calcarata'' (common names thorny devil stick insect and giant spiny stick insect ) is a species of phasmid endemic to Australasia. Range and Habitat ''Eurycantha calcarata'' is native to New Guinea, New Caledonia, and the Solomon I ...

'', ''

Eurycantha horrida Eurycantha horrida, the thorny devil walking stick, is a species belonging to the stick insects ( order Phasmatodea) and to the family Phasmatidae. Description ''Eurycantha horrida'' can reach a length of about in males, of about in females. ...

'', '' Diapheromera veliei'', '' Diapheromera covilleae,'' '' Heteropteryx dilatata'') respond by curling the abdomen upward and repeatedly swinging the legs together, grasping at the threat. If the menace is caught, the spines can, in humans, draw blood and inflict considerable pain. Some species are equipped with a pair of glands at the

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...

(front) edge of the

prothorax The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum ( ventral), and the propleuron ( lateral) o ...

that enables the insect to release defensive secretions, including chemical compounds of varying effect: some produce distinct odors, and others can cause a stinging, burning sensation in the eyes and mouth of a predator. The spray often contains pungent-smelling volatile

metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, ...

s, previously thought to be concentrated in the insect from its plant food sources. However, it now seems more likely that the insect manufactures its own defensive chemicals. Additionally, the chemistry of the defense spray from at least one species, '' Anisomorpha buprestoides'', has been shown to vary based on the insect's life stage or the particular population it is part of. This chemical spray variation also corresponds with regionally specific color forms in populations in Florida, with the different variants having distinct behaviors. The spray from one species, '' Megacrania nigrosulfurea'', is used as a treatment for skin infections by a tribe in

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

because of its

antibacterial An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...

constituents. Some species employ a shorter-range defensive secretion, where individuals bleed reflexively through the joints of their legs and the seams of the

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton ( endoskeleton) in for example, a human. In usage, some of the ...

when bothered, allowing the blood (

hemolymph Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...

), which contains distasteful compounds, to discourage predators. Another ploy is to regurgitate their stomach contents when harassed, repelling potential predators.

Life cycle

The life cycle of the stick insect begins when the female deposits her eggs through one of these methods of

oviposition The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...

: she will either flick her egg to the ground by a movement of the ovipositor or her entire abdomen, carefully place the eggs in the axils of the host plant, bury them in small pits in the soil, or stick the eggs to a substrate, usually a stem or leaf of the food plant. A single female lays from 100 to 1,200 eggs after mating, depending on the species. Many species of phasmids are

, meaning the females lay eggs without needing to mate with males to produce offspring. Eggs from virgin mothers are entirely female and hatch into nymphs that are exact copies of their mothers. Stick insect species that are the product of hybridisation are usually

obligate {{wiktionary, obligate As an adjective, obligate means "by necessity" (antonym ''facultative'') and is used mainly in biology in phrases such as: * Obligate aerobe, an organism that cannot survive without oxygen * Obligate anaerobe, an organism tha ...

parthenogens, but non-hybrids are facultative parthenogens, meaning they retain the ability to mate and their sexual behavior depends on the presence and abundance of males. Phasmatodea eggs resemble seeds in shape and size and have hard shells. They have a lid-like structure called an operculum at the anterior pole, from which the nymph emerges during hatching. The eggs vary in the length of time before they hatch which varies from 13 to more than 70 days, with the average around 20 to 30 days. Some species, particularly those from

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...

regions, undergo

diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press I ...

, where development is delayed during the winter months. Diapause is initiated by the effect of short day lengths on the egg-laying adults or can be genetically determined. Diapause is broken by exposure to the cold of winter, causing the eggs to hatch during the following spring. Among species of economic importance such as '' Diapheromera femorata'', diapause results in the development of two-year cycles of outbreaks. 21 Phasmid Eggs

Many species' eggs bear a fatty, knoblike capitulum that caps the operculum. This structure attracts ants because of its resemblance to the elaiosome of some plant seeds that are sought-after food sources for ant larvae, and usually contribute to ensuring seed dispersal by ants, a form of ant-plant mutualism called

myrmecochory Myrmecochory ( (sometimes myrmechory); from grc, μύρμηξ, mýrmēks ("ant") and ''khoreíā'' ("circular dance") is seed dispersal by ants, an ecologically significant ant–plant interaction with worldwide distribution. Most myrmec ...

. The ants take the egg into their nest underground and can remove the capitulum to feed to their larvae without harming the phasmid embryo. There, the egg hatches and the young nymph, which initially resembles an ant (another instance of mimicry among Phasmatodea), eventually emerges from the nest and climbs the nearest tree to safety in the foliage. The eggs of stick insects have a coating of calcium oxalate which makes them survive unscathed in the digestive tract of birds. It has been suggested that birds may have a role in the dispersal of parthenogenetic stick insect species, especially to islands. The Phasmatodea life cycle is hemimetabolous, proceeding through a series of several nymphal

s. Once emerged, a nymph will eat its cast skin. Adulthood is reached for most species after several months and many molts. The lifespan of Phasmatodea varies by species, but ranges from a few months to up to three years.

Ecology

Phasmids are herbivorous, feeding mostly on the leaves of trees and shrubs, and a conspicuous component of many

neotropical The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In bioge ...

(South American) systems. Phasmatodea has been postulated as dominant

light-gap In ecology, a light gap is a break in Canopy (biology), forest canopy or similar barrier that allows young plants to grow where they would be otherwise inhibited by the lack of light reaching the seedbed. Light gaps form predominantly when a tre ...

herbivores there. Their role in the forest ecosystem is considered important by many scientists, who stress the significance of light gaps in maintaining

succession Succession is the act or process of following in order or sequence. Governance and politics *Order of succession, in politics, the ascension to power by one ruler, official, or monarch after the death, resignation, or removal from office of ...

and resilience in climax forests. The presence of phasmids lowers the net production of early successional plants by consuming them and then enriches the soil by

defecation Defecation (or defaecation) follows digestion, and is a necessary process by which organisms eliminate a solid, semisolid, or liquid waste material known as feces from the digestive tract via the anus. The act has a variety of names ranging f ...

. This enables the late succession plants to become established and encourages the recycling of the tropical forest. Phasmatodea are recognized as injurious to forest and shade trees by defoliation. ''

Didymuria violescens ''Didymuria violescens'', the spur legged phasmid, also known as the violet-winged stick insect, or violet-winged phasma, is a common phasmid native to Australia. Males have distinct spurs and thicker hind legs (the hind have the spurs) which ...

'', '' Podacanthus wilkinsoni'' and '' Ctenomorphodes tessulatus'' in Australia, '' Diapheromera femorata'' in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

and '' Graeffea crouani'' in coconut plantations in the

South Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

all occur in outbreaks of economic importance. Indeed, in the

American South The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, or simply the South) is a geographic and cultural region of the United States of America. It is between the Atlantic Ocean ...

, as well as in

Michigan Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and t ...

and

Wisconsin Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake M ...

, the walking stick is a significant problem in parks and recreation sites, where it consumes the foliage of oaks and other

hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...

s. Severe outbreaks of the walking stick, ''Diapheromera femorata'', have occurred in the

Ouachita Mountains The Ouachita Mountains (), simply referred to as the Ouachitas, are a mountain range in western Arkansas and southeastern Oklahoma. They are formed by a thick succession of highly deformed Paleozoic strata constituting the Ouachita Fold and Thru ...

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the O ...

and

Oklahoma Oklahoma (; Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a state in the South Central region of the United States, bordered by Texas on the south and west, Kansas on the north, Missouri on the northeast, Arkansas on the east, New ...

. The insects eat the entire leaf blade. In the event of heavy outbreaks, entire stands of trees can be completely denuded. Continuous defoliation over several years often results in the death of the tree. Because these species cannot fly, infestations are typically contained to a radius of a few hundred yards. Nevertheless, the damage incurred to parks in the region is often costly. Control efforts in the case of infestations have typically involved chemical

pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and ...

s; ground fires are effective at killing eggs but have obvious disadvantages. In New South Wales, research has investigated the feasibility of controlling stick insects using natural enemies such as parasitic wasps (''Myrmecomimesis'' spp.).

Taxonomy

The classification of the Phasmatodea is complex and the relationships between its members are poorly understood. Furthermore, there is much confusion over the ordinal name. Phasmida is preferred by many authors, though it is incorrectly formed; Phasmatodea is correctly formed, and is widely accepted. However, Brock and Marshall argue: The order Phasmatodea is sometimes considered to be related to other orders, including the

Blattodea Blattodea is an order of insects that contains cockroaches and termites. Formerly, termites were considered a separate order, Isoptera, but genetic and molecular evidence suggests they evolved from within the cockroach lineage, cladistically mak ...

Mantodea Mantises are an order (Mantodea) of insects that contains over 2,400 species in about 460 genera in 33 families. The largest family is the Mantidae ("mantids"). Mantises are distributed worldwide in temperate and tropical habitats. They ha ...

Notoptera The wingless insect order Notoptera, a group first proposed in 1915, had been largely unrecognized since its original conception, until resurrected in 2004. As now defined, the order comprises five families, three of them known only from fossils ...

and

Dermaptera Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forcep-like pincers on their abdomen, and membranous wings folded ...

, but the affiliations are uncertain and the grouping (sometimes referred to as "Orthopteroidea") may be

paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...

(not have a common ancestor) and hence invalid in the traditional circumscription (set of attributes that all members have). Phasmatodea, once considered a suborder of

Orthoptera Orthoptera () is an order of insects that comprises the grasshoppers, locusts, and crickets, including closely related insects, such as the bush crickets or katydids and wētā. The order is subdivided into two suborders: Caelifera – grassh ...

, is now treated as an order of its own. Anatomical features separate them as a

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

(descended from a common ancestor) group from the Orthoptera. One is the instance among all species of Phasmatodea of a pair of

exocrine gland Exocrine glands are glands that secrete substances on to an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous. Exocrine glands are one ...

s inside the prothorax used for defense. Another is the presence of a specially formed

sclerite A sclerite (Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...

(hardened plate), called a vomer, which allows the male to clasp the female during mating. The order is divided into two, or sometimes three, suborders. The most common division is into the suborder groups Anareolatae and Areolatae, which are distinguished according to whether the insect has sunken areola, or circular areas, on the underside of the apices of the middle and hind tibiae (Areolate) or not (Anareolate). However the

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

(evolutionary) relationships between the different groups is poorly resolved. The

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic ...

of Anareolatae has been questioned and the morphology of the eggs may be a better basis for classification. An alternative is to divide the Phasmatodea into three suborders Agathemerodea (1 genus and 8 species), Timematodea (1 genus and 21 species) and

Euphasmatodea The Euphasmatodea, also known by its junior synonym Verophasmatodea is a suborder of the Phasmatodea, which contains the vast majority of the extant species of stick and leaf insects, excluding the Timematodea. The oldest record of Euphasmatodea ...

. for the remaining

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

. This division is, however, not fully supported by the molecular studies, which recover Agathemerodea as nested within Verophasmatodea rather than being the sister group of the latter group. Over 3,000 species have been described, with many more yet to be described both in museum collections and in the wild. While suggestions of have been made that various insects extending back to the

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...

epoch represent stem-group phasmatodeans, the earliest unambigious members of the group are the Susumanioidea, which first appeared during the Middle

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

, and usually have two large pairs of wings. Modern phasmatodeans first appeared during the Early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

, with the cuirrently oldest known being '' Araripephasma'' from the Early Cretaceous (

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

)

Crato Formation The Crato Formation is a geologic formation of Early Cretaceous (Aptian) age in northeastern Brazil's Araripe Basin. It is an important Lagerstätte (undisturbed fossil accumulation) for palaeontologists. The strata were laid down mostly during ...

of Brazil, around 113 million years old, which can be confidently assigned to the Euphasmatodea. The earliest leaf insect (Phylliinae) fossil is ''Eophyllium messelensis'' from the 47-million-year-old

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...

of Messel, Germany. In size and cryptic (leaflike) body form, it closely resembles extant species, suggesting that the behavior of the group has changed little since that time. The Agathemerodea, previously placed at suborder level, is now considered ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

''.

Select species

One Australian species, the Lord Howe Island stick insect, is now listed as critically endangered. It was believed extinct until its rediscovery on the rock known as

Ball's Pyramid Ball's Pyramid is an erosional remnant of a shield volcano and caldera lying southeast of Lord Howe Island in the Pacific Ocean. It is high, while measuring in length and only across, making it the tallest volcanic stack in the world. B ...

. An effort is underway in Australia to rear this species in

captivity Captivity, or being held captive, is a state wherein humans or other animals are confined to a particular space and prevented from leaving or moving freely. An example in humans is imprisonment. Prisoners of war are usually held in captivity by a ...

. The best known of the stick insects is the Indian or laboratory stick insect (''

''). This insect grows to roughly 10 cm (4 in) and reproduces parthenogenically, and although males have been recorded, they are rare. Fossils of the extinct genus and species '' Eoprephasma hichensi'' have been recovered from

Ypresian In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian ...

age sediments in the U.S. state of

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

and

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, for ...

, Canada. The species is one of the youngest members of the stem phasmatodean group Susumanioidea.

Phasmids in Europe

In Europe there are 17 species of stick insects described, belonging to the genera ''

Bacillus ''Bacillus'' (Latin "stick") is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum '' Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural ''Bacill ...

'' ''

Clonopsis ''Clonopsis''Pantel L (1915) ''Bull. Soc. entomol. Fr.'' 1915: 96. is a stick insect genus in the family Bacillidae BacillidaeBrunner von Wattenwyl C (1893) ''Annali del Museo Civico di Storia Naturale Giacomo Doria, Genova'' (2)13(33): 101. i ...

'', '' Leptynia'' and '' Pijnackeria''. There are also a few other species that live in Europe but are introduced, as for example with a couple of species of '' Acanthoxyla'', which are native to New Zealand but are present in southern England. In the Iberian Peninsula there are currently described 13 species and several subspecies. Their life cycle is annual, living only during the hottest months (especially genera ''Leptynia'' and ''Pijnackeria''), which usually means late spring to early autumn. File:LeafInsect.jpg,

Phyllium ''Phyllium''Illiger (1798) ''Verzeichnis der Käfer Preussens'' 499. is the largest and most widespread genus of leaf insects in the family Phylliidae (Phasmatodea). They can be found in Sundaland, Philippine Islands, Wallacea, and Australasi ...

sp., from the Western Ghats. File:Clonopsis gallica01.jpg, ''

Clonopsis gallica ''Clonopsis gallica'', the French stick insect, is a stick insect species in the genus ''Clonopsis ''Clonopsis''Pantel L (1915) ''Bull. Soc. entomol. Fr.'' 1915: 96. is a stick insect genus in the family Bacillidae BacillidaeBrunner von Wat ...

''. File:Ctenomorpha chronus02.jpg, Ctenomorpha marginipennis. File:Leptynia hispanica.png, Leptynia hispanica.

Behavior

Stick insects, like

praying mantis Mantises are an order (Mantodea) of insects that contains over 2,400 species in about 460 genera in 33 families. The largest family is the Mantidae ("mantids"). Mantises are distributed worldwide in temperate and tropical habitats. They ha ...

es, show rocking behavior in which the insect makes rhythmic, repetitive, side-to-side movements. The common interpretation of this behavior's function is it enhances

by mimicking vegetation moving in the wind. These movements may also be important in allowing the insects to discriminate objects from the background by relative motion. Rocking movements by these generally sedentary insects may replace flying or running as a source of relative motion to help them discern objects in the foreground. Mating behavior in Phasmatodea is impressive because of the extraordinarily long duration of some pairings. A record among insects, the stick insect '' Necroscia sparaxes'', found in India, is sometimes coupled for 79 days at a time. It is not uncommon for this species to assume the mating posture for days or weeks on end, and among some species ('' Diapheromera veliei'' and '' D. covilleae''), pairing can last three to 136 hours in captivity. Overt displays of aggression between males over mates suggests that extended pairing may have

evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variati ...

to guard females from sperm competition. Fighting between competing males has been observed in the species ''D. veiliei'' and ''D. covilleae''. During these encounters, the approach of a challenger causes the existing mate to manipulate the female's abdomen, which he has clasped by means of the clasping organ, or vomer, down upon itself to block the site of attachment. Occasionally, the consort will strike out at the competitor with the mid femora, which are equipped with an enlarged and hooked spine in both sexes that can draw the blood of the opponent when they are flexed against the body to puncture the integument. Usually, a strong hold on the female's abdomen and blows to the intruder are enough to deter the unwanted competition, but occasionally the competitor has been observed to employ a sneaky tactic to

inseminate Insemination is the introduction of sperm into a female’s reproductive system for the purpose of impregnating, also called fertilizing, the female for sexual reproduction. The sperm is introduced into the uterus of a mammal or the oviduct of a ...

the female. While the first mate is engaged in feeding and is forced to vacate the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

position, the intruder can clasp the female's abdomen and insert his

genitalia A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...

. If he is discovered, the males will enter into combat wherein they lean backward, both clasped to the female's abdomen, and freely suspended, engage in rapid, sweeping blows with their forelegs in a manner similar to

boxing Boxing (also known as "Western boxing" or "pugilism") is a combat sport in which two people, usually wearing protective gloves and other protective equipment such as hand wraps and mouthguards, throw punches at each other for a predetermined ...

. Usually, when the intruder gains attachment to the female's abdomen, these conflicts result in the displacement of the original mate. Carausius morosus

Lengthy pairings have also been described in terms of a defensive alliance. When cleaved together, the pair is more unwieldy for predators to handle. Also, the chemical defenses (secretions, reflex bleeding, regurgitation) of the individual stick insect are enhanced when two are paired. Females survive attacks by predators significantly better when pairing, largely because the dorsal position of the male functions well as a shield. This could indicate that manipulation by females is taking place: if females accept

ejaculate Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential componen ...

at a slow rate, for instance, the males are forced to remain ''in copulo'' for longer and the female's chances of survival are enhanced. Also, evolution could have simply favored males that remained attached to their females longer, since females are often less abundant than males and represent a valuable prize, so for the lucky male, even the sacrifice of his own life to preserve his

offspring In biology, offspring are the young creation of living organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a brood or progeny in a more general way. This ca ...

with the female may be worthwhile.

Sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...

in the species, where females are usually significantly larger than the males, may have evolved due to the fitness advantage accrued to males that can remain attached to the female, thereby blocking competitors, without severely impeding her movement. Certain Phasmatodea, such as ''Anisomorpha buprestoides'', sometimes form aggregations. These insects have been observed to congregate during the day in a concealed location, going their separate ways at nightfall to forage, and returning to their refuge before dawn. Such behavior has been little studied, and how the insects find their way back is unknown.

In human culture

Leaf Insects and Stick Insects Marianne North

Stick insects are often kept in captivity: almost 300 species have been reared in laboratories or as pets. The most commonly kept is the Indian (or laboratory) stick insect, ''

'', which eats vegetables such as lettuce. Droppings of the stick insect ''Eurycnema versirubra'' (Serville, 1838) ''Eurycnema versifasciata''fed with specific plants are made into a medicinal tea by Malaysian Chinese to treat ailments. The

botanical illustrator Botanical illustration is the art of depicting the form, color, and details of plant species, frequently in watercolor paintings. They must be scientifically accurate but often also have an artistic component and may be printed with a botanical ...

Marianne North Marianne North (24 October 1830 – 30 August 1890) was a prolific English Victorian biologist and botanical artist, notable for her plant and landscape paintings, her extensive foreign travels, her writings, her plant discoveries and the ...

(1830–1890) painted leaf and stick insects that she saw on her travels in the 1870s. Tribesmen in

Sarawak Sarawak (; ) is a state of Malaysia. The largest among the 13 states, with an area almost equal to that of Peninsular Malaysia, Sarawak is located in northwest Borneo Island, and is bordered by the Malaysian state of Sabah to the northeast, ...

eat phasmids and their eggs. Some indigenous people of the

D'Entrecasteaux Islands D'Entrecasteaux Islands () are situated near the eastern tip of New Guinea in the Solomon Sea in Milne Bay Province of Papua New Guinea. The group spans a distance of , has a total land area of approximately and is separated from the Papua New G ...

have traditionally made fishhooks from the legs of certain phasmids. Research has been conducted to analyze the stick insect method of walking and apply this to the engineering of six-legged

walking robot Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults ov ...

s. Instead of one centralized

control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial ...

, it seems each leg of a phasmid operates independently. In

and

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

many kinds of stick insects are kept as

exotic pet An exotic pet is a pet which is relatively rare or unusual to keep, or is generally thought of as a wild species rather than as a domesticated pet. The definition varies by culture, location, and over time—as animals become firmly enough est ...

s including the strong,

goliath Goliath ( ) ''Goləyāṯ''; ar, جُليات ''Ǧulyāt'' (Christian term) or (Quranic term). is a character in the Book of Samuel, described as a Philistine giant defeated by the young David in single combat. The story signified King Sau ...

, spiny and

children's A child ( : children) is a human being between the stages of birth and puberty, or between the developmental period of infancy and puberty. The legal definition of ''child'' generally refers to a minor, otherwise known as a person young ...

. The custom of keeping stick insects as pets was probably brought to Australia by either Chinese, Japanese or Vietnamese immigrants during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

, the

Korean War {{Infobox military conflict , conflict = Korean War , partof = the Cold War and the Korean conflict , image = Korean War Montage 2.png , image_size = 300px , caption = Clockwise from top:{ ...

or the

Vietnam War The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...

. Stick insects have been kept as pets since the time of the

Han dynasty The Han dynasty (, ; ) was an Dynasties in Chinese history, imperial dynasty of China (202 BC – 9 AD, 25–220 AD), established by Emperor Gaozu of Han, Liu Bang (Emperor Gao) and ruled by the House of Liu. The dynasty was preceded by th ...

. They were kept inside

birdcage A birdcage (or bird cage) is a cage designed to house birds as pets. Antique (or antique-style) birdcages are often popular as collectors' items or as household decor but most are not suitable for housing live birds, being too small, improper ...

s and people in the Far East believe they bring good luck and

fortune Fortune may refer to: General * Fortuna or Fortune, the Roman goddess of luck * Luck * Wealth * Fortune, a prediction made in fortune-telling * Fortune, in a fortune cookie Arts and entertainment Film and television * ''The Fortune'' (1931 film) ...

, just like

crickets Crickets are orthopteran insects which are related to bush crickets, and, more distantly, to grasshoppers. In older literature, such as Imms,Imms AD, rev. Richards OW & Davies RG (1970) ''A General Textbook of Entomology'' 9th Ed. Methuen 8 ...

References

External links

The Phasmid Study Group

Phasmatodea.com

Phasmida Species File

New Zealand Stick Insect Web Site

ASPER: Lesser Antilles and French stick insects
{{DEFAULTSORT:Phasmatodea Insect orders Articles containing video clips Cenomanian first appearances Extant Late Cretaceous first appearances Orthopterida