Can grasshopper moult

Can grasshopper moult

All grasshoppers begin their lives as eggs. Yet eggs represent the least known stage of the grasshopper life cycle. They are laid in the soil of the habitat and develop hidden from the view of humans. Eggs of a few species, however, have been studied in both field and laboratory (Fig. 9).

Figure 9. One intact and one broken egg pod, exposing the eggs of the migratory grasshopper, Melanoplus sanguinipes (Fabricius).

Incubation of eggs begins immediately after females deposit them in the soil. The embryo, at first a tiny disc of cells laying on the ventral side of the yolk surface and at the posterior end of the eggs (Fig. 10), grows rapidly, receiving nourishment from the nutrient stores in the yolk.

From left to right: Stage 1 (5%) Stage 3 (10%) Stage 7 (20%) Stage 10 (30%) Stage 12 (40%) Stage 19 (50%)

Figure 10. Selected stages in the development of a grasshopper embryo (Melaoplus sanguinipes) held at a constant temperature of 30 C. Left two figures show whole egg; other figures show embryos removed from egg. (Illustrations adapted from Riegert, 1961; stages idetified and designated for embryos of Aulocara elliotti by Saralee Visscher, 1966).

In seven days the embryo of the migratory grasshopper, Melanoplus sanguinipes , held at an incubation temperature of 30½C, reaches Stage 19. In this stage the embryos of many rangeland species such as Aulocara elliotti and Camnula pellucida cease growth and begin a diapause . The embryo of the migratory grasshopper, however, continues to develop and at Stage 20 actively moves from the ventral to the dorsal surface and revolves 180½ on its long axis (see Figure 10, Stage 20). After 15 days the embryo has grown to Stage 24, having achieved 80 percent of its development. It then ceases growth and enters diapause. The embryo of the twostriped grasshopper, and probably others also, enter diapause at this stage. Exposed to favorable incubation temperatures, the eggs of a few rangeland species, such as Arphia conspersa and Xanthippus corallipes , develop completely and hatch during the same summer they are laid. The immediate cause of cessation of embryonic growth (diapause) in eggs of the majority of rangeland grasshoppers appears to be the shutdown of growth hormones. The embryos remain physiologically active as transfer of nutrient materials from the yolk into the embryonic fat body and other tissues continues. Cold temperatures of winter, however, slow or end this process and embryos enter a dormant period.

For eggs laid in temperate regions to reach their maximum development before diapause, they must receive sufficient heat, usually measured as day-degrees of heat accumulated in the soil at egg depth. Eggs deposited late in the season or during a cold summer may not receive this amount of heat, especially in northern areas such as the Canadian provinces of Alberta, Manitoba, and Saskatchewan. Eggs that do not reach their potential stage of development have reduced hatchability the following spring and thus do not contribute as much to the maintenance of a population.

During winter, low ground temperatures eventually break egg diapause. As soon as the ground warms above threshold soil temperatures of 50 to 55½F in spring, the embryos are ready to continue their development. Research has shown that for the few species studied, eggs need 400 day-degrees by fall to attain maximum embryonic growth and another 150 day-degrees in spring to initiate hatching. For completion of embryonic growth from start to finish, eggs require totals of 500 to 600 day-degrees.

In spring the emergence of hatching grasshoppers may be readily observed. All embryos of a single pod usually wriggle out one after another within several minutes. Once out, they immediately shed an embryonic membrane called the serosa. An individual hatchling, lying on its side or back and squirming, takes only a few minutes to free itself (Fig. 11). During this time the hatchlings are susceptible to predation by ants. After the shedding of the membrane the young grasshoppers stand upright and are able to jump away and escape attacking predators. In spring, young grasshoppers have available green and nutritious host plants. The majority of individuals in grasslands are grass feeders, but individuals of some species are mixed feeders, eating both grasses and forbs. Others are strictly forb feeders.

Figure 11. The lifecycle of the bigheaded grasshopper, Alucara ellliotti (Thomas). During summer in bare spots of grassland the female deposits at intervals batches of eggs. As soon as the eggs are laid, they begin embryonic development and reach an advanced stage in which they enter diapause and pass the winter. In spring the eggs complete embryonic devlopment and hatch. The young grasshopper sheds a serosal skin, the exoskeleton hardens, and the nymph begins to feed and grow. After molting five times and developing through five instars in 30-40 days, it becomes an adult grasshopper with functional wings. The adult female matures groups of six to eight eggs at a time and deposits them in the soil at intervwls of three to four days for the duration of her short life.

As insects grow and develop, they molt at intervals, changing structures and their form. This process is called metamorphosis . A number of insects undergo gradual (simple) metamorphosis, such as grasshoppers. With this type of metamorphosis the insect that hatches looks like the adult except for its smaller size, lack of wings, fewer antennal segments, and rudimentary genitalia (Fig. 11). Other insects with gradual metamorphosis include the true bugs, aphids, leafhoppers, crickets, and cockroaches. The majority of insects undergo complete (complex) metamorphosis, as the eggs hatch into wormlike larvae adapted for feeding and have a vastly different appearance from that of the adult insect. Before full-grown larvae can become adult insects they must enter into the pupal stage. In this stage they develop and grow the adult structures. Common examples of insects that undergo complete metamorphosis are beetles, butterflies, bees, wasps, and flies.

For young grasshoppers to continue their growth and development and reach the adult stage, they must periodically molt or shed their outer skin (Fig. 11). Depending on species and sex, they molt four to six times during their nymphal or immature life. The insect between molts is referred to as an instar; a species with five molts thus has five instars. After shedding the serosal skin, the newly hatched nymph is the first instar. After each molt the instar increases by one so that the nymph consecutively becomes a second, third, fourth, and fifth instar. When the fifth instar molts, the grasshopper becomes an adult or an imago.

The new adult has fully functional wings but is not yet ready to reproduce. The female has a preoviposition period of one to two weeks during which she increases in weight and matures the first batch of eggs. Having mated with a male of her species, the female digs a small hole in the soil with her ovipositor and deposits the first group of eggs. Once egg laying begins, the female continues to deposit eggs regularly for the rest of her short life. Depending on the species, production may range from three pods per week to one pod every one to two weeks. The species that lay fewer eggs per pod oviposit more often than those that lay more eggs per pod.

The egg pods of grasshoppers vary not only in the number of eggs they contain but also in their size, shape, and structure. Based on structure, four types have been recognized. In type I a stout pod forms from frothy glue and soil surrounding the eggs; froth is lacking between the eggs. In type II a weaker pod is formed from frothy glue between and surrounding the eggs. In type III frothy glue is present between the eggs but does not completely surround them. In type IV only a small amount of froth is secreted on the last eggs of a clutch, and most of the eggs lie loosely in the soil. Grasshopper eggs themselves vary in size, color, and shell sculpturing. Depending on the species eggs range from 4 to 9 mm long and may be white, yellow, olive, tan, brownish red, or dark brown. Eggs of certain species are two-toned brown and tan.

Events in the life cycle of an individual species of grasshopper — hatching, nymphal development, and adulthood — occur over extended periods. The eggs may hatch over a period of three to four weeks. Nymphs may be present in the habitat eight to ten weeks and adults nine to 11 weeks. Because of the overlapping of stages and instars, raw field data obtained by sampling populations do not answer several important questions. For example, how many eggs hatched? How many individuals molted successfully to the next instar? What was the average duration of each instar? How many became adults? What was the average length of life and the average fecundity of adult females? To obtain answers to these questions, detailed sampling data must be treated mathematically.

Laboratory data may also be used in studying grasshopper life histories. Table 4 provides information on the life history of the migratory grasshopper, Melanoplus sanguinipes , reared at a constant temperature of 86½F and 30-35% relative humidity and fed a nutritious diet of dry feed, green wheat, and dandelion leaves. The entire nymphal period averages 25 days for males and 30 days for females. Each instar takes four to five days to complete development except for the last instar, which takes seven days. Adult longevity of males averages 51 days and females, 52 days. Longevity of adults in the field is no doubt briefer because of the natural predators and parasites cutting short the lives of their prey.

TABLE 4. Life history of the migratory grasshopper, Melanoplus sanguinipes, reared in the laboratory at a constant temperature of 86.5 F.

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A Grasshopper’s Life Cycle

The grasshopper is a flying animal belonging to order Orthoptera and class Insecta. About 11,000 species exist. They are herbivorous and commonly seen in autumn; a few appear in summer and spring. During mating the male grasshopper deposits sperm into the female’s vagina, which finds its way to the eggs through canals known as micropyles. An adult grasshopper goes through the stages egg, nymph and adult, and has a lifespan of approximately one year.

This is the initial stage of a grasshopper’s life cycle. The mother grasshopper lays fertilized eggs in midsummer, and they remain 1 or 2 inches under the sand or in leaf litter. She sprinkles them with a sticky semisolid substance that sets to form an egg pod. Each egg pod contains 15 to 150 eggs, depending on the species. Normally a female grasshopper can lay up to 25 pods. The eggs remain underneath for about 10 months in autumn and winter before hatching into nymphs during spring or in the initial days of summer.

This is the second stage of the grasshopper’s life cycle and the initial stage during which a young grasshopper sees the outside world. Nymphs look like adult grasshoppers, called molts, apart from the fact that they are wingless and lack reproductive organs. They undergo five substages known as instars before fully developing into adult grasshoppers; each instar is characterized by shedding of the cuticle skin and gradual growth of wings. In order to survive, nymphs start to feed on succulent and soft plant foliage barely one day after hatching from the egg. This stage lasts for about five to six weeks before the young nymphs mature to adult grasshoppers.

Molting takes place during the nymph stage. The locust sheds its exoskeleton before maturing into an adult. While the exoskeleton covers the nymph’s body, providing it with protection against external injuries, it inhibits its growth because of its rigidity and inability to give room for expansion. The nymph has to shed it in order to achieve growth. It undergoes five to six molts in which it changes its structure and form before reaching adulthood.

This is a fully grown grasshopper. It takes about one month before the wings are fully developed. The mature grasshopper is more mobile than the nymph, a characteristic that helps them to hunt and flee from predators. The reproductive organs are fully grown, so the females can lay eggs and the males can fertilize. However, female grasshoppers do not lay eggs until they are 1 or 2 weeks old, to allow them to gain enough weight before they start laying eggs. Once she starts laying eggs, the female continues to lay eggs at intervals of three to four days until she dies. Adult grasshoppers live for about two months, depending on the weather.

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Naturalist’s Corner

Ask the question “Do you look like your parents?”, to insects. The young ones of grasshoppers, bugs and cockroaches will answer “yes”, while butterflies and beetles will say “no”.

All these insects start life as an egg. The young ones of butterflies and beetles look very unlike their parents when they are born. They go through an intermediate dormant stage (pupa) before they eventually transform into adults. Grasshoppers, bugs and cockroaches look like miniatures of their parents when they are born, and have to moult many times as they grow into adults.

Moulting is a process where the insect changes into new “clothes” by shedding their old skin that has grown tight. Most insects need to change their “clothes” at some point of time in their life as they grow, just like we need to buy a new wardrobe as we grow bigger.

Insects have an exoskeleton (i.e. they have their skeleton on the outside). This can become a problem to a growing insect, unless the exoskeleton is discarded periodically making room for growth. Insects achieve this by moulting from time to time. They shed their old, small exoskeleton so that they can grow a new one that is bigger. The exoskeleton can also expand when it is new and still soft. It gradually hardens and no growth is possible until it moults again.

The process of moulting is complicated and can take several hours. During this time, the insect is very vulnerable as it cannot escape from predators and therefore, it tries to hide during the moulting process.

During the time spent out in the wilderness, I have had several opportunities to see the moult (shed skin) of insects like grasshoppers and praying mantids clinging on to plants like ghosts of their owners. But, only on this occasion was I lucky to witness a grasshopper in the process of shedding its skin, and was even luckier to have a camera on me to document the event!

Karthikeyan S

Karthikeyan S. is the Chief Naturalist at Jungle Lodges & Resorts Ltd

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Can grasshopper moult

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Dungeness crab shells washed up on a beach in Washington State.

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The Magic of Molting

Some animals shed their exoskeletons, skins, and more as they grow

Back in April, the Washington State Department of Fish and Wildlife began receiving numerous phone calls and emails from concerned residents. Many had spotted an alarming sight along Cherry Point beach a few miles south of the Canadian border: thousands of crabs washed up on the sand. The department sent officials out to investigate. Upon closer inspection, they discovered that what covered the beach wasn’t dead crabs, but their empty shells—the result of a natural process called molting.

Many animals undergo molting as a means of shedding their outer layer—feathers, hair, skin, or exoskeleton—so they can grow bigger or prepare for their next life stage. “It’s a critical event in the life cycle of an organism,” says Donald Mykles, a biologist at Colorado State University.В

Back in April, the Washington State Department of Fish and Wildlife received a lot of phone calls and emails from worried people. They had spotted an alarming sight on a beach a few miles south of the Canadian border. It looked like thousands of crabs had washed up on the sand. The department sent officials out to investigate. After getting a closer look, they discovered that dead crabs weren’t covering the beach. It was just their empty shells. This was the result of a natural process called molting.

Many animals undergo molting in order to shed their outer layer. This lets them grow bigger or prepare for their next life stage. Animals might shed feathers, hair, skin, or an exoskeleton. An exoskeleton is a hard outer skeleton that protects an animal’s body. “It’s a critical event in the life cycle of an organism,” says Donald Mykles, a biologist at Colorado State University.В

Humans have skin and bones that stretch and grow with us over time, but animals like the Dungeness crab in Washington have rigid outer bodies that can’t expand to accommodate their growth. Instead, these animals undergo multiple molts as they mature into adults.

All arthropods—including crustaceans, spiders, and insects—must regularly go through the molting process. But animals like snakes, birds, and dogs molt too.

“There are lots of different organisms that molt,” says Mykles, “but the process is very, very different for each one.” Read on to learn more about how and why different species molt.

Humans have skin and bones that stretch and grow with us over time. But animals like the Dungeness crab in Washington have rigid outer bodies. Their bodies can’t expand with them as they grow. Instead, these animals undergo multiple molts as they mature into adults.

All arthropods, including crustaceans, spiders, and insects, must regularly go through the molting process. But animals like snakes, birds, and dogs molt too.

“There are lots of different organisms that molt,” says Mykles. “The process is very, very different for each one.” Read on to learn more about how and why different species molt.

Molting not only lets crabs grow larger, but it also allows them to get rid of parasites and barnacles that might be living on their old shells. They can also regenerate lost legs! A typical crab molts between 30 and 40 times in its lifetime.

When a crab is ready to molt, it starts forming a soft paper-thin shell under its existing one. It also absorbs extra nutrients it will use later to harden its new shell.

The crab sucks in water to expand its body and split the old shell open. Then it starts wiggling out of the shell—a process that can take up to three hours.

The crab fully exits its old shell. But it leaves behind its esophagus, stomach lining, and part of its intestine in the old shell. It must regrow these parts.

The crab pumps more water into its body to increase its size. With a vulnerable soft shell, it will go into hiding until the shell hardens.

Molting not only lets crabs grow larger, but it also allows them to get rid of parasites and barnacles that might be living on their old shells. They can also regenerate lost legs! A typical crab molts between 30 and 40 times in its lifetime.

When a crab is ready to molt, it starts forming a soft paper-thin shell under its existing one. It also absorbs extra nutrients it will use later to harden its new shell.

The crab sucks in water to expand its body and split the old shell open. Then it starts wiggling out of the shell—a process that can take up to three hours.

The crab fully exits its old shell. But it leaves behind its esophagus, stomach lining, and part of its intestine in the old shell. It must regrow these parts.

The crab pumps more water into its body to increase its size. With a vulnerable soft shell, it will go into hiding until the shell hardens.

During its year-long life, a grasshopper develops from an egg to a nymph to an adult. Molting occurs five to six times, but only during the nymph stage. That’s when it resembles a small adult without wings. Unlike other arthropods, which molt throughout their entire lives, most insects—including grasshoppers—stop molting once they become adults.

When it’s time to molt, a grasshopper’s body produces hormones that signal it can no longer support its increasing mass. The insect then begins to grow a new exoskeleton inside its old one. “It’s like growing a sleeping bag inside a sleeping bag,” says John Ewer, an entomologist at the University of Valparaíso in Chile.

Once the new shell is ready, the insect gulps in as much air as possible and breaks out of its old shell. Then it quickly attaches its muscles and nerves to the new shell. In this state they are easy prey for predators, “so they molt as quickly as possible, often in a few minutes,” says Ewer.

Grasshoppers live only for a year. In that time, it develops from an egg to a nymph to an adult. It molts five to six times, but only during the nymph stage. That’s when it resembles a small adult without wings. Most arthropods molt throughout their entire lives. But most insects, including grasshoppers, stop molting once they become adults.

A grasshopper knows it’s time to molt because its body produces a special hormone. This chemical signal tells the grasshopper’s body that’s it’s time to molt. The insect then begins to grow a new exoskeleton inside its old one. “It’s like growing a sleeping bag inside a sleeping bag,” says John Ewer. He studies insects at the University of ValparaГ­so in Chile.

Once the new shell is ready, the insect gulps in as much air as possible and breaks out of its old shell. Then it quickly attaches its muscles and nerves to the new shell. In this state the insects are easy prey for predators. “They molt as quickly as possible, often in a few minutes,” says Ewer.

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Moulting of a grasshopper

Amy Tsang came across a grasshopper that she managed to photograph while accompanying KC to Pasir Ris Park on a spider mission.

Wrote Amy: “I was very thrilled when I realised I had spotted a grasshopper which was newly moulted. I had not seen one before in this state. The new wings were light yellow in colour and looked soft and fresh. It looked like a ‘skirt’ when viewed at certain angles (above, below).

“The grasshopper was pretty still when it first moulted. In one of my pixs, its eyes look like they were closed to me, and I wondered if the moulting process took its toil on the grasshopper and now it was actually very tired and catnapping!” added Amy.

“Looking closer at this grasshopper, whose identity I have yet to know, it seemed to have the strangest looking eyes! There were bands of dashes across its eyeball. I wondered why, as most insects don’t seem to spot such ‘banded’ eyes,” continued Amy.

The image above shows it at rest. That below shows it’s wings folded up in the ‘normal’ position assumed by grasshoppers.

Zoologist and avid naturalist Dr Leong Tzi Ming identified the grasshopper as Xenocatantops humilis, a rather common species of grassland and forest edge. “However, although it may be a common and widespread species, certain momentary aspects of its life, such as moulting and mating are seldom documented. So this is a refreshing contribution,” added Tzi Ming.

A newly hatched grasshopper, known as a nymph, has no wings and thus cannot fly. It needs to go through about five stages before becoming a fully mature adult with wings and all. Each stage, known as a moult, involves shedding its exoskeleton and replacing it with a new one. This is necessary as the exoskeleton cannot expand as the body increases in size with each stage of growth. The above encounter most probably shows the final stage of moulting as the grasshopper emerges as a fully adult individual.

Amy Tsang (text and images) & Dr Leong Tzi Ming (grasshopper ID)
Singapore
November 2014

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