Details Discus About Locusts And Grasshoppers

Locusts are huge herbivore insects which can pose serious threats of crops because of their capacity to form dense, highly mobile groups of insects. They are a species of grasshoppers with short-horns. They create large numbers in large groups that migrate, with individuals that differ in many traits from individuals living in separate groups.

Then, in Australia There are 3 major insects that cause problems to locust

• The Australian pest is a locust ( Chortoicetes terminifera)
• The spur-throated locust ( Austracris guttulosa)
• The migration-related the locust ( Locusta migratoria)

The three species are all from Australia. They are all part of the same insect family like katydids, grasshoppers, and crickets which is the Orthoptera.

The difference between Locusts and grasshoppers

The two species are identical in appearance, however locusts are able to exist in two distinct behavioural states (solitary and social) however, most grasshoppers don’t. If the density of population is low, the locusts act as individuals, similar to grasshoppers. However, when the locust populations are high, the animals undergo physiological and behavioral changes, referred to as polyphenism of the phase, and they form large, sloppy-behaving groups of nymphs, or swarms of adults.

In addition to the changes in behavior, changes in phase can occur in conjunction with changes to body shape and colour as well as changes in fertility, physiology and longevity. These changes are so significant in some species that forms that swarm and those that do not initially thought to be separate species. The size of the population growth and the frequency of migrations are also a way to distinguish species that are known as locusts from grasshoppers.

The distinction between grasshoppers and locusts is not always clear in the sense that the degree to which species display the gregarious characteristics of their phase is classified. The migratory species has all the characteristics related to phase changes that are characterized by differences in the body’s shape and colour as well as fertility and gregarious behavior in both the nymphal and adult life stages, and forming large swarms and bands. It is also known as the Australian plague locust can also form large nymph bands as well as adult swarms, but it does not show changes in body color. The spur-throated locusts do not make bands, and adult females do not lay eggs in large numbers, however, they do form large crowds.

Clacification Of Locusts

The Locusts are part of the same group as grasshoppers and crickets, which is crickets – Orthoptera (derived by the Greek words orthos which means straight or rigid , and Ptera meaning wings).

Within Australia there are more than 2800 varieties of Orthoptera and more than 700 species of grasshoppers and locusts. Many species are still to be described scientifically.

The table below outlines the three major insect species that are a pest within Australia can be classified currently.

Identification of Male and Female Locusts

Female and male species of locusts can be identified by the form of the apex of the abdomen:

Male The tip of the abdomen smooth and smooth and

Female The abdomen’s tip is sharp

The abdominal area at the end of male locusts is rounded because of the sub-genital plate which hides all reproductive organs.

The abdomen’s end in the female locust is pointed because of the jaws of the lower and upper jaws of the ovipositor.

On average, male locusts are smaller than females from the same species. But, size isn’t an adequate way to determine the gender of a locust because it is dependent on the quality and quantity of food consumed during the stage of nymphs.

Lifecycle Of All Locusts

The Locust undergoes a direct or incomplete metamorphosis. As opposed to insects, such as moths or butterflies they do not have a pupal stage. The juveniles appear similar to adults.

There are three primary phases of development namely egg, nymph and mature. The nymph stage, also known as the stage known as the hopper is separated into stages of growth referred to as instars, and moulting in between each. The following diagram illustrates the development for the Australian plague locust with five stages of instar. The dates for development are estimates for optimal conditions in the summer months.

The eggs of the locust are laid in the soil. Females drill through the soil by using the ovipositor located at the top of the abdomen and then lay eggs in a “pod” that are sealed with the froth. The froth is used to shield eggs from desiccation diseases and predation.

Following the completion of each instar, this nymph leaves or moults, its skin to continue growing. At the time of hatching, the nymph is not wingless, but with each moult, the developing wing buds expand in size. They are used to figure out the stage of growth of Nymphs.

The final stage of moulting into an adult state is referred to as fledging. It is in which the locust has fully-formed flying wings. It can take a few weeks prior to the time when the adults in the young stages of the majority of species begin to lay eggs.

Green vegetation is essential to ensure the survival of nymphs and adults in adult migration, egg development.

How long it takes a locust species to reach maturity is dependent on the species conditions, habitat and the temperature. Nymphs and adults can manage their bodies temperature through basking under the sunlight or moving into shade.

Enemies Of Locusts

Egg parasites

A variety of tiny wasps (3-5 millimeters long) that belong to the Genus Scelio parasitize eggs of locusts as well as grasshoppers. Scelio fullgidus is among the most widespread species found in the inland regions and is the main eggs parasite for the Australian plague locust. Populations of S. Fulgidus rise during outbreaks of locust and can result in very high mortality of eggs.

The female burrows down into the froth plug at the top of the locust egg and then uses a retractable needle-shaped ovipositor to put eggs inside every locust egg. After hatching the wasp larva consumes eggs and destroys embryo of the locust. If the conditions are dry S. fulgidus can lie dormant inside the locust egg for up to a month before emerging following rain.

Adult female Scelio fulgidus

Flies (Diptera)

Different species of fly have been found to be parasites for locusts. They typically occur in areas with higher rainfall and may kill or diminish the fertileness of locusts.

Blaesoxipha spp. (sarcophid blowflies) are a frequent parasite that has an extremely rapid development of 4 to 6 days during the summer. Female fly larvae deposit tiny maggot-like larvae directly on locust, which penetrates the cuticle. The fully developed larva emerges from the wall of the locust’s body then pupates within the soil. The parasite can live for several generations per year. It is not usually fatal to the adult, however females that are parasitized lay smaller eggs. Nymphs typically die shortly after the appearance from the parasite.

Ceracia Fergusoni (tachinid flying insect) is parasite that has a resemblance to Blaesoxipha. Female fly glues eggs directly to their body. This is a characteristic of the locust. When the eggs hatch, a tiny larva burrows its way through the bottom of the egg before entering the host. After being fully fed (10-14 days after the hatching) the larva is released from its locust by pushing its way through the body’s segments. The pupation process takes place within the soil with the adult fly emerges within 12-15 days.

Trichopsidea Oestracea (bee-fly) Females drop thousands of eggs on the ground , or on dead dead wood like tree stumps or fence posts. The larvae that hatch in a free manner and then enter a locust or grasshopper’s Spiracle (breathing gap). The majority of larvae develop inside each host , and after being released from the host, it digs a hole in soil to develop into pupa. The pupae that pupate in the autumn develop into adults in spring, during the nymphal stage of development for locusts. There is a lesser second generation that develops in summer. The highest levels of parasitism have been reported in dry weather. The parasitized locusts don’t mature eggs and typically die before the larva of the fly emerges.

Mites

The Tarsonemid Mites (tracheal mites) are often neglected because they are found within the locust’s the tracheae (breathing organs). Their eggs are visible on the dorsal face of the locust, when its wings expand.

Leptus Sp. (body mites) is an adult red mite that can be found on the bodies and wings, particularly of the old locusts. The host is not usually affected.

Nematodes

Nematodes (round worms) are important parasites of locusts as well as grasshoppers in areas of high rainfall However, they are not often encountered in areas with lower rainfall.

Amphimermis Sp. is a significant parasite of grasshoppers with no wings ( Phaulacridium vittatum). Eggs are laid on soil, and the hatching process is triggered by rain. After hatching, the worm larvae move to the surface of the soil which they then track and penetrate grasshoppers or locusts. They stay within the host for a few weeks, causing developmental delays and preventing sexual maturation. The host dies as the nematode appears to go back into the earth.

Nematode worm that is grasshoppers with no wings.
(Photo from M.Hill (Photo by M.Hill Baker in 1991. NSW Agriculture)

Mermis spp. Nematodes lay eggs on the vegetation that may be eaten by locusts. The eggs hatch inside the gut , and the larva of the nematode enters the wall of the gut and feeds inside the body cavity and eventually kills the locust after their emergence.

Protozoans

It isn’t known much about the protozoan parasites found in locusts and are often neglected. Protozoans form cysts and attach to the middle-gut lining of locusts. In the guts of parasitised host appears yellow. many parasites can affect digestion, lower female fecundity , or even eliminate the locust.

Bacteria, fungi and viruses

The spores that cause a fungus infection are not often found in the wild, and this could be because of the general aridity of the area in which outbreaks can occur. But, a particular strain that is part of this mold Metarhizium acridum initially found in spur-throated locusts was created as biopesticide by CSIRO and has been utilized to control the APLC since 2001. the APLC since 2001.

Bacteria and viruses that infect Australian locusts are not well-known and are not well understood, however the high rate of mortality in NSW in spring 2010 was due to a bacterial illness in the dense, moist vegetation during a time of intense rainfall.

Predators

Many mammals, birds and insects feed on locusts however generally, they are not specific feeders and haven’t been proven to have an effect on the numbers of locusts in an outbreak. Vertebrate predators are, unlike other parasites, can’t grow rapidly to benefit from an outbreak of locusts and their appetites are quickly satisfied. Some nomadic and migratory birds gather to eat high-density locusts.