Grasshoppers are insects that belong to the suborder Caelifera of the order Orthoptera. There are around 18,000 different species of grasshoppers, but they can be divided into 2 main groups, according to the length of their antennae: long-horned and short-horned grasshoppers. The short-horned ones usually (though not always) refer to locusts. Grasshoppers are typically ground-dwelling insects with powerful hind legs which enable them to escape from threats by leaping vigorously. When the population of grasshoppers is very high and the environmental conditions are of appropriate nature, some species of grasshoppers can change colour and behaviour and form swarms; when this happens, they are more commonly referred to as locusts.
No matter their form, grasshoppers are voracious eaters, that devour cereals, vegetables and pasture, especially when they swarm together. This makes them a very dangerous pest, capable to destroy crops over large areas.
In some countries, such as Mexico, China, Indonesia, and various areas of the Arab world, grasshoppers are used as food, being said to provide an important source of protein.
Description and distribution
As is the case with most insects, a grasshopper’s body can be divided into 3 segments: head, thorax, and abdomen.
Starting with the head, grasshoppers present a pair of large compound eyes, which provide a broad field of vision and information regarding colour, shape, distance, and movement, as well as 3 simple eyes (ocelli) on the forehead, which detect light intensity. A pair of thin antennae are responsible for the sense of touch and smell, seeing as they contain olfactory and touch receptors, but they are short and do not reach very far. The mouthparts are downward-directed, specially adapted for chewing, and contain gustatory receptors. Two sensory palps lie in front of the jaws.
The thorax and abdomen are both segmented. The thorax is made out of 3 segments, which bear 3 pairs of legs and 2 pairs of wings. The legs all end in claws that are adapted for gripping, with the hind legs being particularly powerful, specially adapted for leaping. In the cuticle of the legs, there are special receptors that are responsible with sensing pressure. The forewings are narrow and leathery, while the hind wings are large, membranous, and much more powerful. The muscles that control these limbs lie in the interior of the thorax.
The abdomen is made out of 11 segments. The first segment is fused to the thorax and contains the auditory organ and the tympanum, which are membranes that vibrate in response to sound waves, allowing the grasshopper to distinguish sounds. Segments 2 through 8 are ring-shaped and joined by flexible membranes, while segments 9 through 11 are reduced. Segment 9 presents a pair of cerci. Segments 10 and 11 house the reproductive organs.
Numerous fine hairs covering all 3 sections of the grasshoppers’ bodies act as mechanoreceptors (touch and wind sensors), being most dense on the antennae, the palps, and the cerci. Overall, an adult grasshopper’s body measures between 1-7cm, depending on the species. Female grasshoppers are usually larger than the males, and present short ovipositors (sharp points at the end of the abdomen) that are used to lay eggs. Males, on the other hand, may sometimes have special structures on the wings; they rub these together or they use them to rub their hind legs with, creating sounds that attract females.
Perhaps the most defining characteristic of a grasshopper is its powerful jump. A large, adult grasshopper can jump as much as a meter (a total of 20 body lengths) without using its wings. They do so by extending their large, powerful back legs and pushing against a substrate (be it the ground, a twig, a blade of grass, etc.), which results in them being catapulted into the air. These jumps are used for a variety of reasons, ranging from escaping a predator to simply moving from place to place. Although they do it rarely, grasshoppers are also able to fly, reaching a speed of up to 12km/h.
In terms of predators, grasshoppers have a variety of them at each stage of their life. Bee-flies, ground beetles, and blister beetles eat grasshopper eggs. Insects such as ants, robber flies, and sphecid wasps, spiders, many birds, and even small mammals eat the nymphs and adults. Grasshoppers are also affected by a variety of parasites and diseases. Some examples include blowflies, fleshflies, tachinid flies, and mites. Spinochordodes tellinii and Paragordius tricuspidatus are parasitic worms that, interestingly enough, alter the behavior of grasshoppers, persuading them to leap into a nearby body of water, causing them to drown, but allowing the parasite in question to advance to the next stage of its life cycle, which occurs in the water. Diseases can be caused by bacteria, numerous viruses, fungi, and protozoa.
To protect themselves from as many of these predators as possible, grasshoppers put to use a variety of methods that enable them to avoid detection, to escape if detected, or to avoid being eaten if unable to escape. In the first instance, they often use camouflage, being aided by a coloration that allows them to blend into the background. Some species can even change this colouring according to their surroundings, becoming green if they are close to leafy vegetation, sandy in open areas, or grey if they are surrounded by rocks. Some grasshoppers use their colouring in a different manner, startling predators with brilliantly-coloured wing-flashes; these, coupled with energetic jumps, give them time to escape. Other species, such as the rainbow grasshopper (Dactylotum bicolor), are aposematic; this means that they have a special “warning coloration” that signal genuine toxicity to the predators. This toxicity may come from the toxic plants that some species knowingly eat, and the toxins that are subsequently kept in their bodies, and it usually manifests through a brown liquid that grasshoppers “spit” onto their predators. Adult grasshoppers are also able to launch themselves in the air and fly, escaping the immediate danger.
The Caelifera have a predominantly tropical distribution with fewer species known from temperate zones, but most of the superfamilies have representatives worldwide. They are almost exclusively herbivorous and are probably the oldest living group of chewing herbivorous insects.
Breeding and dietary information
Grasshoppers are hemimetabolous insects, which means that they do not undergo complete metamorphosis. A typical grasshopper’s life is comprised out of 3 stages: egg, nymph, and adult. After mating, female grasshoppers a hole with their ovipositor and lay eggs in pods in the ground that are close to food sources, covering the hole immediately with soil and litter. This generally happens during the summer. What exactly happens next depends on the species. In some (most) species, eggs enter diapause after a couple of weeks of development, passing the winter in this stage, while in others, they hatch in the same summer that they are laid. In species where the eggs enter diapause, development is resumed as soon as the ground warms above a certain threshold temperature. When the time comes, all the eggs in a pod usually hatch out at once, within a few minutes of each other. Soon, the grasshoppers shed their membranes and their exoskeletons harden. Although a nymph usually undergoes about 5 moults before becoming an adult, it is able to jump away from predators from the very first instar.
Grasshoppers most often inhabit grassy fields, meadows, and forest areas, and are most active during the day, but can also feed at night. They have no nests and no demarcated territories, with some species willing to migrate long distances in search of a new supply of food. Most species are solitary, coming together only to mate, although migratory species sometimes do gather in groups of as many as billions of individuals.
Most of them are herbivorous, eating vegetation from a variety of sources (including cereals, vegetables, pastures, etc.), but some are omnivorous, completing their diets with animal tissue and faeces. An adult grasshopper can eat up to 16 times its own weight.
Grasshoppers as pests
Because of their diet, grasshoppers can become serious pests, eating large quantities of foliage and affecting everything from pasture to vegetables. They also thrive in the sun, so a drought can stimulate their development and cause an increase in a population. When they form swarms and become locusts, they can completely decimate wide areas of crops, consuming not only the foliage of plants, but also the stems, flowers, fruits, seeds, and even bark. As a result, such swarms can have devastating effects on human populations, causing famines and upheavals. In 1954, for example, in Kenya, a desert locust swarm reportedly consumed over 200 square km of both wild and cultivated plants.
The best way of preventing grasshoppers from becoming pests is by manipulating the environment. Shade will discourage them from developing, but their movement could also be hindered by removing coarse vegetation and field margins. By doing this and discouraging luxurious vegetation growth, grasshoppers will be prevented from easily moving onto developed crops. An infestation with grasshoppers can be prevented with the use of repellents, both natural and chemical ones, and you can get rid of an infestation can be achieved by using natural predators of grasshoppers, organic insecticides, or chemical ones.