The Caelifera includes some 2,400 valid genera and about 11,000 known species. This information is not available from fossil specimens, and the palaentological taxonomy is founded principally on the venation of the hindwings. Morphological classification is difficult because many taxa have converged towards a common habitat type recent taxonomists have concentrated on the internal genitalia, especially those of the male. The first modern families such as the Eumastacidae, Tetrigidae and Tridactylidae appeared in the Cretaceous, though some insects that might belong to the last two of these groups are found in the early Jurassic. The group diversified during the Triassic and have remained important plant-eaters from that time to now. In evolutionary terms, the split between the Caelifera and the Ensifera is no more recent than the Permo-Triassic boundary the earliest insects that are certainly Caeliferans are in the extinct families Locustopseidae and Locustavidae from the early Triassic, roughly 250 million years ago. Orthopteraįossil grasshoppers at the Royal Ontario Museum The Ensifera (crickets, etc.), Caelifera and all the superfamilies of grasshoppers except Pamphagoidea appear to be monophyletic. The phylogeny of the Caelifera, based on mitochondrial ribosomal RNA of thirty-two taxa in six out of seven superfamilies, is shown as a cladogram. They may be placed in the infraorder Acrididea and have been referred-to as "short-horned grasshoppers" in older texts to distinguish them from the also-obsolete term "long-horned grasshoppers" (now bush-crickets or katydids) with their much longer antennae. Although "grasshopper" is sometimes used as a common name for the suborder in general, some sources restrict it to the more "advanced" groups. Grasshoppers belong to the suborder Caelifera.
The study of grasshopper species is called acridology. They feature in art, symbolism and literature. They are used as food in countries such as Mexico and Indonesia.
Even in smaller numbers, the insects can be serious pests. Swarms of locusts can have devastating effects and cause famine, having done so since Biblical times. Grasshoppers have had a long relationship with humans. The eggs are subject to attack by parasitoids and predators. Grasshoppers are affected by parasites and various diseases, and many predatory creatures feed on both nymphs and adults. Other species such as the rainbow grasshopper have warning coloration which deters predators. They protect themselves from predators by camouflage when detected, many species attempt to startle the predator with a brilliantly-coloured wing-flash while jumping and (if adult) launching themselves into the air, usually flying for only a short distance. Grasshoppers are plant-eaters, with a few species at times becoming serious pests of cereals, vegetables and pasture, especially when they swarm in the millions as locusts and destroy crops over wide areas. Under these circumstances, they are known as locusts.
At high population densities and under certain environmental conditions, some grasshopper species can change color and behavior and form swarms. The grasshopper hears through the tympanal organ which can be found in the first segment of the abdomen attached to the thorax while its sense of vision is in the compound eyes, the change in light intensity is perceived in the simple eyes (ocelli). As hemimetabolous insects, they do not undergo complete metamorphosis they hatch from an egg into a nymph or "hopper" which undergoes five moults, becoming more similar to the adult insect at each developmental stage. Grasshoppers are typically ground-dwelling insects with powerful hind legs which allow them to escape from threats by leaping vigorously. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshoppers are a group of insects belonging to the suborder Caelifera. American grasshopper ( Schistocerca americana)
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