Stick insects are insects well known for their camouflage.
Stick insects are also knwn as stick-bugs, walking sticks, bug sticks, phasmids, ghost insects and leaf insects.
They belong to the order Phasmatodea – The order’s name is derived from the Ancient Greek φάσμα phasma, meaning an apparition or phantom
There are about 3,000 species of stick insects.
Stick insects are found in all continents except Antarctica. They are most numerous in the tropics and subtropics.
Over 300 species are known from the island of Borneo, making it the richest place in the world for stick insects.
Their natural range is very broad; they occur at high and low altitudes, in temperate and tropical temperatures and in dry or wet conditions. Stick insects generally live in trees and bushes, but some species live entirely on grassland.
Like any insect, stick insects have a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae.
Some species have wings and can disperse by flying, while others are more restricted.
Stick insects very in size from 1.5 centimeters (0.6 in) to about 60 centimeters (24 in) in length; males are typically much smaller than females.
In 2014 a new species of stick insect in southern China has been declared the world’s longest insect. The 62.4-centimeter (24.6-inch) long creature beats the previous record holder, another stick insect discovered in 2008 (and named Phobaeticus chani or Chan’s megastick) by nearly 6 centimeters (2.4 inches).
Some species have cylindrical stick-like bodies, while others have flattened, leaflike shapes.
Stick insects generally mimic their surroundings in color, normally green or brown, although some may be black, gray, or even blue.
A few species, such as Carausius morosus, are even able to change their pigmentation to match their surroundings – like a chameleon.
Many species have a rocking motion, where the body sways from side to side, like leaves or twigs swaying in the breeze.
When camouflage is not enough, some stick insects use active forms of defense to handle predators. For example, the species Eurycantha calcarata can release an awful-smelling substance as a deterrent. Other species have brightly colored wings that are invisible when folded against their body; when they feel threatened, they flash open their wings, then immediately drop to the ground and again hide their wings.
Stick insects are mainly nocturnal creatures, spending much of their day motionless, hidden under plants, helping them avoid many predators.
Stick insects are herbivores meaning that the diet of the stick insect is purely a vegetarian one. Stick insects mainly feed on leaves and other green plants. Some are very specialized, feeding only upon a favored plant species. Others are generalists.
Their droppings contain broken-down plant material that becomes food for other insects.
One of the most interesting facts about stick insects is their ability to reproduce parthenogenetically. This is a form of asexual reproduction where the unfertilized females produce eggs that hatch into females. If a male fertilizes the egg, it has a fifty-fifty chance of turning out male. If no males are around, the line continues with females only.
A single female lays from 100 to 1,200 eggs, depending on the species. Eggs resemble seeds in shape and size, and have hard shells. Incubation lasts from 3 to 18 months.
Stick insect hatchlings, called nymphs, hatch from the egg as miniature versions of adults. They then go through successive molts to eventually reach adult size. This process is called incomplete metamorphosis: egg, nymph, and adult. Molting happens when the old exoskeleton is shed, and the larger body that had grown inside it expands and hardens into a new one. Most walkingsticks eat skin they have shed after a molt to recycle proteins and to keep their location a secret from predators. [Photo below: stick insect nymph]
Adulthood is reached for most species after several months and many molts.
The lifespan of stick insects varies by species, but ranges from a few months to up to three years.
Stick insects, unfortunately for them, can provide a lot of nourishment to a handful of different predator types. Common predators for these insects include primates, spiders, rodents, reptiles and birds. Bats are also a prominent and serious predation threat for these insects.
Many stick insects are easy to care for, and make good pets. Almost 300 species have been reared in captivity. The most commonly kept is the Indian (or laboratory) stick insect, Carausius morosus, which eats vegetables such as lettuce.
Research has been conducted to analyze the stick insect method of walking and apply this to the engineering of six-legged walking robots. Instead of one centralized control system, it seems each leg of a phasmid operates independently.