Stick insect

The stick insect is an amazing creature of interest to naturalists. About 2500 species of these insects make up the ghost order. Due to their appearance, they are known as masters of camouflage (mimicry). Stick insects skillfully imitate different parts of vegetation: green stems, bizarre foliage, dried branches. This phenomenon is commonly called phytomimicry, which in Greek means phyton — plant, and mimikos — imitation. Females of some species reproduce by parthenogenesis, which means that the young come from completely unfertilized eggs.

Origin of the species and description

Photo : Stick insect

Photo: Stick insect

The classification of ghosts (Phasmatodea) is complex, and the relationships between its members are poorly understood. In addition, there are many misunderstandings about the ordinal name of the members of this group. Therefore, the taxonomy of stick insects is subject to frequent changes and is sometimes very controversial. This is partly due to the fact that new species are constantly being discovered. On average, since the end of the 20th century, several dozen new taxa appear annually. The results are often reviewed.

Interesting fact: In a paper published in 2004 by Oliver Zompro, Timematodea was removed from the order of stick insects and placed with stoneflies (Plecoptera) and embioptera (Embioptera). Only in 2008, two other major works were carried out, which, in addition to creating new taxa down to the subfamily level, also led to the redistribution of many taxa to the family level.

The oldest fossil stick insects were discovered in the Triassic in Australia. Early members of the family are also found in Baltic, Dominican, and Mexican amber (Eocene to Miocene). In most cases, these are larvae. From the fossil family Archipseudophasma tidae, for example, the species Archipseudophasma phoenix, Sucinophasma blattodeophila and Pseudoperla gracilipes from Baltic amber are described.

At present, depending on the source, many species are considered to be of the same type as the aforementioned species or, like Balticophasma lineata, are placed in their own genus. In addition to this, the fossil record also suggests that the ghosts once had a much wider range. Thus, in the Messel quarry (Germany), a 47-million-year-old leafworm print named Eophyllium messelensis was found.

Appearance and features

Photo: What a stick insect looks like

Photo: What a stick insect looks like

The length of the stick insect ranges from 1.5 cm to over 30 cm in length. The heaviest species is Heteropteryx dilatata, the females of which can weigh up to 65 g. Many species are wingless or have reduced wings. The thorax of winged species is much shorter than that of wingless forms. In winged forms, the first pair of wings is narrow and keratinized, while the hind wings are wide, with straight veins along the length and many transverse veins.

Video: Stick insect

The chewing jaws are the same in different species of stick insects. The legs are long and slender. Some of them are capable of limb autotomy (regeneration). Some have long, thin antennae. In addition, insects have a complex eye structure, but only a few winged males have photosensitive organs. They have an impressive visual system that allows them to perceive the details of their surroundings even in dark conditions, which is consistent with their nocturnal lifestyle.

Fun fact: Stick insects are born with tiny compound eyes with a limited number of facets. As they grow through successive molts, the number of facets in each eye increases along with the number of photoreceptor cells. The sensitivity of an adult eye is ten times greater than that of a newborn.

As the eye becomes more complex, the mechanisms for adapting to dark/light changes also improve. The larger size of adult insect eyes makes them more susceptible to radiation damage. This explains why adults are nocturnal. The reduced sensitivity to light in newly hatched insects helps them escape from the fallen leaves in which they hatch and move up into brighter foliage.

An insect in a defensive posture is in a state of catalepsy, which is characterized by waxy flexibility of the body. If the stick insect is given some pose at this time, he will remain in it for a long time. Even the removal of one of the parts of the body will not affect its condition. The sticky pads on the feet are designed to provide extra grip when climbing, but are not used on level ground

Where does the stick insect live?

Photo: Stick insect

Photo: Stick insect

The stick insect can be found in ecosystems all over the world, with the exception of Antarctica and Patagonia. They are most numerous in the tropics and subtropics. Species biodiversity is highest in Southeast Asia and South America, followed by Australia, Central America and the southern United States. Over 300 species inhabit the island of Borneo, making it the richest place in the world for horror stories (Phasmatodea).

There are approximately 1500 known species in the eastern region, while 1000 species are found in the neotropical areas and more than 440 species in Australia. In the rest of the range, the number of species in Madagascar and throughout Africa, as well as from the Near East to the Palearctic, decreases. There are only a few native species in the Mediterranean and the Far East.

Fun fact: One of the species of stick insects living in Southeast Asia, the largest insect in the world. Females of the genus Phobaeticus — the world's longest insects, reaching a total length of 56.7 cm in the case of Phobaeticus chani, including extended legs.

Habitats with lush vegetation have the highest density of species. Chief among these are forests, and especially various types of tropical forests. In drier areas, the number of species decreases, as well as in higher altitude, and therefore colder regions. Representatives of the genus Monticomorpha have the largest range and they are still located at an altitude of 5000 meters near the snow line on the Ecuadorian volcano Cotopaxi.

Now you know where the stick insect lives. Let's see what it eats.

What does the stick insect eat?

Photo: Stick insect in nature

Photo: Stick insect in nature

All ghosts are phytophages, that is, herbivores. Some of them are mono-phages specialized for certain types of plants or groups of plants, for example, Oreophoetes Peruana that eats ferns exclusively. Other species are very general eaters and are considered omnivorous herbivores. For eating, they usually only lazily walk through food crops. During the day, they stay in one place and hide on food plants or on the ground in the leaf layer, and with the onset of darkness they begin to show activity.

Stick insects eat the leaves of trees and shrubs, nibbling them with stable jaws. They feed at night to avoid the main enemies. But even complete darkness does not guarantee complete safety for insects, so the ghosts behave extremely carefully, trying to create less noise. Most species feed alone, but some species of Australian stick insects move in large flocks and can destroy all the leaves in their path.

Since members of the order are phytophages, individual species may also appear as pests on crops. Thus, in the botanical gardens of Central Europe, insects are occasionally found that managed to escape and escape as pests. Stick insects from India (Carausius morosus), from Vietnam (Artemis), as well as the insect Sipyloidea Sipylus were found, which caused significant damage, for example. B. in the Botanical Garden of Munich. The danger of animals escaping, especially in tropical regions, is quite high, the relationship of some species or entire groups of insects requires research.

Character and Lifestyle Features

Photo: Stick insect from the Red Book

Photo: Stick insect from the Red Book books

Stick insects, like praying mantises, exhibit certain swaying movements in which the insect makes rhythmic, repetitive movements from side to side. A common interpretation of this behavioral function is that it enhances crypsis by mimicking vegetation moving in the wind. However, these movements may be the most important, as they allow insects to distinguish objects from the background using relative movement.

The swinging motions of these normally sessile insects can replace flying or running as a source of relative motion to help them distinguish objects in the foreground. Some stick insects, such as Anisomorpha buprestoides, sometimes form large groups. These insects have been observed to congregate during the day in a hidden place, wandering around at night to forage and returning to their roost before dawn. This behavior has been little studied, and how the insects find their way back is unknown.

An interesting fact: The time of development of embryos in an egg is, depending on the species, approximately from three to twelve months, in exceptional cases — up to three years. The offspring turn into adult insects after three — twelve months . Particularly in brightly colored species, it often differs in color from its parents. Species with no or less aggressive coloration show the bright colors of their parents later, such as Paramenexenus laetus or Mearnsiana bullosa.

Among ghosts, adult females live on average much longer than males, namely from three months to a year, and males usually only three to five months. Some of the stick insects only live for about a month. The largest recorded age, over five years, was reached by a wild-caught female Haaniella scabra from Sabah. In general, many members of the Hetropterygigae family are extremely long-lived.

Social Structure and Reproduction

Photo: Giant stick insect

Photo: Giant stick insect

Stick insect mating in some pairs is impressive in its duration. The record among insects shows the Necroscia species, found in India, whose mating games last for 79 days. It is not uncommon for this species to assume a mating posture for days or weeks on end. And in species such as Diapheromera veliei and D. covilleae, mating can last from three to 136 hours. Fighting between competing males is observed in D. veiliei and D. covilleae. During these encounters, the rival's approach forces the male to manipulate the female's abdomen to block the attachment site.

From time to time the female strikes at the competitor. Usually a strong grip on the female's belly and blows to the intruder is enough to keep unwanted competition at bay, but occasionally a competitor uses sly tactics to inseminate the female. While the female's mate is feeding and is forced to vacate the dorsal space, the intruder may grasp the female's abdomen and insert their genitals. Usually, when the intruder gains access to the female's abdomen, this results in the replacement of the former partner.

Interesting fact: Most of the stick insects, in addition to the usual method of reproduction, can produce offspring without a partner, laying unfertilized eggs. Thus, they are not necessarily dependent on males, as fertilization is not required. In the case of automatic parthenogenesis, a set of haploid chromosomes of the egg, cubs are born exact copies of the mother.

For the further development and existence of the species, the participation of males is necessary to fertilize part of the eggs. It is easy for stick insects living in packs to find partners — it is more difficult for species accustomed to being alone. Females of these species secrete special pheromones that allow them to attract males. 2 weeks after fertilization, the female lays voluminous, seed-like eggs (somewhere up to 300). The offspring that emerge from the egg after metamorphosis is completed tend to get to the food source faster.

Natural enemies of stick insects

Photo: Stick insect

Photo: Stick Insect

The main enemies of the ghosts are birds that look for food in the grass, as well as among the leaves and branches. The main defense strategy of most stick insects — in camouflage, more precisely imitation of dead or living parts of plants.

Usually, stick insects resort to such methods of camouflage protection:

  • remain still even when touched and do not try to escape or resist;
  • sway, imitating the swaying parts of plants in the wind;
  • change their daytime light color to darker at night due to the release of hormones. The influence of hormones can cause orange-red grains to accumulate or expand in colored skin cells, resulting in a discoloration;
  • simply sink to the ground where they are difficult to see between other parts of the plant;
  • quickly fall to the ground, and then, seizing a minute, quickly run away;

  • some species frighten attackers by stretching their wings to appear larger;
  • others make noises with wings or tentacles;
  • to avoid predators, many species may shed individual limbs at marked fracture points between the femur and femur ring and replace them almost entirely during the next skinning (regeneration).

Ghosts also have the so-called military glands. Such species exhale their watery secretions through openings in their chests that are located above their front legs. The secretions can either smell strongly and are usually unappetizing, or even contain very harsh chemicals. Especially members of the Pseudophasmatidae family have aggressive secretions that are often corrosive and in particular affect the mucous membranes.

Another common strategy of larger species such as Eurycanthini, Extatosomatinae and Heteropteryginae is to kick enemies. Such animals extend their hind legs, turned in the air, and remain in this position until the enemy approaches. Then they strike with their legs joined together at the opponent. This process is repeated at irregular intervals until the opponent gives up or is trapped, which can be quite painful due to the spikes on the hind legs.

Population and Species Status

Photo: What a stick insect looks like

Photo: What a stick insect looks like

Four species are listed in the Red Book as endangered species, two species are on the verge of extinction, one species is listed as endangered, and another species is extinct.

These species include:

  • Carausius scotti is critically endangered, endemic to the small island of Silhouette, which is part of the Seychelles archipelago;
  • Dryococelus australis is on the verge of extinction. It was practically destroyed on Lord Howe Island (Pacific Ocean), brought there by rats. Later, thanks to the newly found specimens, a program was launched to breed them in captivity;
  • Graeffea seychellensis is an almost extinct species that is endemic to the Seychelles;
  • Pseudobactricia ridleyi is a completely extinct species. It is now known from a single specimen discovered 100 years ago in the tropics on the Malay Peninsula in Singapore.

Serious damage to forestry can occur, especially in monocultures. From Australia to South America, introduced species Echetlus evoneobertii in Brazilian eucalyptus — whose plantations were in grave danger. In Australia itself, Didymuria violescens tends to cause serious damage to the upland forests of New South Wales and Victoria every two years. Thus, in 1963, hundreds of square kilometers of eucalyptus forest were completely neutralized.

Stick insect protection

Photo: Stick insect from the Red Book

Photo: Stick insect from the Red Book

Little is known about the threat to ghostfish populations due to their secretive lifestyle. However, habitat destruction and the introduction of predators often have a huge impact on species living in very small areas such as islands or natural habitats. The appearance of the brown rat on Lord Howe Island in 1918 led to the fact that the entire population of Dryococelus australis was already considered extinct in 1930. Only the discovery of a population of less than 30 animals 23 km from the neighboring island of Ball's pyramid proved its survival. Due to the small size of the population and because the habitat of the animals found there was limited to only 6 m × 30 m, it was decided to carry out a breeding program.

Repeated visits to certain habitats show that this is not an isolated case. For example, Parapachymorpha spinosa was discovered in the late 1980s near Pak Chong station in Thailand. Especially for species with a small distribution area, protective measures are initiated by specialists and enthusiasts. Discovered in 2004 by a stick insect in northern Peru, the velvet beetle (Peruphasma schultei) is found in just five hectares.

Because there are other endemic species in the area, it has been protected by the Peruvian government. The NGO INIBICO (a Peruvian environmental organization) was part of the charity. A project for residents of the Cordillera del Condor National Park has also started a breeding program for the velvet freak. The project, which was scheduled to start before the end of 2007, was aimed at saving or selling half of the offspring. Thanks to phasmid lovers, this species has been preserved in its inventory and at present the stick insect is one of the most common phasmids in the terrarium.

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