Walkingstick insects are any of the three thousand spices of highly camouflaged insects. This insect moves at snail speed, but their resemblance to twigs or sticks helps them avoid predators. They move in such a fashion it looks like a twig stirring in the air. Apparently, the insects appear to be a stick, as the name suggests.
The average length of a walkingstick can be from one to twelve inches (2.5 to 30 centimetres), depending on the genus. Some species have unique defence systems like a pointed spine, pungent smell, the spray of a repulsive chemical through exoskeleton joints. Female walk sticks are larger than male ones; one species can grow up to twenty inches (51 centimetres), with legs extended. The eggs of these insects look like seeds. Stick insects mostly survive in tropical and temperate areas. Tropical and rainforest are their preferred habitat as they can easily camouflage among twigs and leaves.
In the world of insects, Walkingstick has a special niche for its regenerative traits; rejuvenating legs and tentacles. Some species have short and fibrous front wings, coupled with colourful large rear wings. The largest walking stick insect falls under Phryganistria Chinensis, measuring up to two feet (62.4 centimetres). Other large species, Phobaeticus kirbyi and Phobaeticus chain can develop up to twelve inches (30 centimetres) habitat in Borneo. Many birds and animals eat stick insects, but bats are the most effective predator. As bats use echolocation to detect the location of prey, the cover-up technique of a walking stick insect becomes fruitless.
Types of Walking Stick Insect
Earlier, a walking stick insect was considered to be in the same class as Orthoptera (crickets and grasshoppers). Later these insects are nomenclature as Phasmatodea. The average lifespan of stick animal and leaf insects is one year in natural habitat; in confinement, they live longer. There are over three thousand species of stick animal.
1. Leaf Insects
Leaf insects, also known as walking leaves, are mostly found in South Asia, Southeast Asia, islands in the Indian Ocean, and Australia. Leaf insects can measure from twenty-eight to a hundred millimetres (1.1 to 3.9 inches); females tend to be larger than males. Female insects are characterized by large front wings attached close to the abdomen. Due to the absence of hind wings, they cannot fly. On the contrary, a male has small forewings supplemented with transparent operational hind wings.
The walking stick bug is one of the many species that can reproduce parthenogenetically. Females hatch unfertilized eggs, and new female insects emerge from them. The eggs look like seeds and are hidden in places where they cannot be easily detected. The hatched insects are devoid of wings, red or brown in colour. After nourishing from leaves, the body colour changes to green.
The defence mechanism of leaf mimicry adopted by a walking stick bug is detailed. The structure of wings, legs, and vein structure of female insects closely look like a leaf from every aspect. Their movement is similar to leaves moving in the wind. Some species even develop a pattern that resembles damaged foliage with crack.
Orthopterans are related to a stick insect order Phasmatodea; cockroaches order Blattodea, and mantids order Mantodea. Orthopteran means straight wing referring to narrow rubbery forewings. These forewings are mainly used for protection, not to fly. All insects under this nomenclature are saltatorial, signifying their wings are adopted mainly for jumping. Long hind legs are the distinctive feature of this species.
Amongst the Orthoptera, cockroaches and mantids are classified under Dictyoptera, despite sometimes categorized under Blattodea and Mantodea correspondingly. Blattodea and Mantodea are suborders of Dictyoptera.
Tropical regions all over the world are breeding grounds of Orthopterans. In the summer months tropical areas are perfect for their thriving; it becomes evident from their large numbers and chirping sound. Zoologists have been fascinated by cockroaches, one of the giant walking stick bugs. Cockroaches are one of the oldest and dreaded Dictyoptera species. A good number of the 24,000 species of orthopterans are plant eaters with large chewing mouthparts jutting out from underneath the head. Locusts are infamous for their destruction of crops.
Orthopterans are visually weird, with long ovipositor used for laying eggs, two pairs of wings closely attached to the body, and hind legs evolved for jumping. Body size ranges from a few centimetres to thirty centimetres. A giant walking stick bug resembles tree twigs; smaller one look like leaves. Orthopterans are Hemimetabolous; that is, there are three life cyclers; egg, multiple nymphs, and adults. The young ones are a miniature version of the adults, except the head looks bigger as the wings are underdeveloped, which look like wing buds.
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A cockroach is a typical example of varied size among orthopterans. For example, attaphila ( tiny wingless cockroach) lives in ant nests that are only two millimetres long. In contrast, Megaloblatta, a South American variant, can grow to ten centimetres, with a wingspan of nineteen centimetres, one of the giant walking stick bugs.
Till now, 24,000 species of orthopterans have been discovered. In the US, one can find 1,300 species of orthopterans, in Europe six hundred species, only thirty-five species habitat in Great Britain. Though orthopterans live worldwide, most thrive in tropical regions, few are found in cold temperate areas. There are twenty mantis species and twenty-seven walking stick bugs in the southern part of the US, but Central and South America are infested with six hundred stick animals and four hundred mantis species. This figure showcases their preferred habitat.
Orthopterans are Hemimetabolous; a gradual metamorphosis occurs in the life span. There are three life stages in Hemimetabolous; egg, nymph, and adult. Usually, the eggs are laid outside the body in-ground or foliage; however, in few cases, like viviparous cockroaches, the eggs are nurtured within the female body. Nymphs born out of the eggs appear similar to adults except for the smaller body, reproductive, and wing size. In most orthopterans species, the hatched insect is more of a developed embryo devoid of fully formed legs enclosed in a thin film.
This stage is called vermiform larva; then, the thin membrane melts out at intermediate moult. The juvenile grasshoppers shed the transparent, formless skin and wriggle out from eggshells; mantids do the same. This phenomenon is known as exuviae. The development stage from intermediate moult to adulthood varies from four to thirteen; cockroaches 5-13; mantids 4-9; grylloblattidae 8; grasshoppers 4-9; and walking sticks 4-6.
Every species of orthopterans have a unique egg-laying process. Among cockroaches, only one species is viviparous; the other four families lay well-casted eggs. Few species carry the ootheca jutting out from the body till the hatching time; others lay the egg within a few days of formation. The ootheca usually contain a few to more than thirty eggs arranged in two chains. There is a ridge-like formation on one edge of the ootheca; the structure varies in species that carry it outwardly. A minuscule pore from the surface to the core of the ootheca acts as an aeration system; this phenomenon occurs in some species. It is interesting to know about stick insect ventilation. The keel remains in the uppermost position during incubation but reversed while depositing.
Mantis lay eggs in bunches ranging from ten to more than three hundred. The clusters of eggs are covered with a viscous liquid acting as a protective cover. The egg assortments have distinctive shapes and sizes. Most mantis lay an egg on vegetation, but some lay it on rocks or in sand holes as per the prevailing environment. Grylloblattidae lay eggs in damp foliage, rotting logs, or in a fissure of rocks or soil. The eggs are usually black in colour and three millimetres long.
Insects play a pivotal role in nature; they act as a catalyst in the decomposition of fungi, bacteria, and other microorganisms, which in turn fertilize the soil. The maggots of flesh flies and blowflies accelerate the decomposition of carrion. Insects dispense and consume bacteria for optimal ecological balance. Insects and flowers have evolved hand in hand; insects facilitate the pollination of flowers.
Certain insects provide products that have commercial value, like silk, dye, honey, and silk. On the other hand, insects cause immense agricultural damage as they feed on many types of organic substances. Insects destroy crops both infield and storage and spread infectious microorganisms to humans, crops, and farm animals. Entomologists study the relationship between insects to humans, the environment, and other organisms. They hugely contribute to forest, agricultural, veterinary and medical entomology.
Damages Commercial Products
When insects cause structural damage to timber, building, foliage, they become pests. Insects like tineid moths and dermestid beetles can consume keratin in hair and feathers, thus destroying skin, fur, wool garments, and carpets. Insect pests of relatively large size like cockroaches, wasps, and flies are noticeable. Micro pests cause enormous damage to the food industry from field to transportation, processing, storage, distribution, and homes. Entomologists are concerned about stick insect pests as they destroy around 20% of world crop production annually. This food damage by pests is more prominent in developing countries due to poor food storage and distribution systems.
Insects are found in every ecology system ranging from arid regions to tropical ones. Insects are found in high-altitude glaciers, streams, low land ponds, and other stagnant water bodies. Their adaptive nature is remarkable; they can survive in 1/10th salinity of seawater, few species survive on the surface of the sea, and some fly larvae can thrive in a container of crude petroleum. Five hundred kinds of insects can be found in one square yard of damp rich soil surface; the number can extend to two thousand in the North Temperate Zone. In one acre of irrigated land, there can be four million insects.