Invertebrates are still more popular pets. The group includes 97% of all animal species ? all animals except those in the Chordate subphylum Vertebrata (fish, reptiles, amphibians, birds and mammals). 3 most popular invertebrates pets are:
Beetles are a group of insects which have the largest number of species. They are placed in the order Coleoptera, which means "sheathed wing" and contains more described species than in any other order in the animal kingdom, constituting about twenty-five percent of all known life-forms. Forty percent of all described insect species are beetles (about 350,000 species), and new species are frequently discovered. Estimates put the total number of species, described and undescribed, at between 5 and 8 million.
Beetles can be found in almost all habitats, but are not known to occur in the sea or in the polar regions. They interact with their ecosystems in several ways. They often feed on plants and fungi, break down animal and plant debris, and eat other invertebrates. Some species are prey of various animals including birds and mammals. Certain species are agricultural pests, such as the Colorado potato beetle Leptinotarsa decemlineata, the boll weevil Anthonomus grandis, the red flour beetle Tribolium castaneum, and the mungbean or cowpea beetle Callosobruchus maculatus, while other species of beetles are important controls of agricultural pests. For example, coccinellidae ("ladybirds" or "ladybugs") consume aphids, scale insects, thrips, and other plant-sucking insects that damage crops.
Tarantula is the common name for a group of "hairy" and often very large spiders belonging to the family Theraphosidae, of which approximately 900 species have been identified. Tarantulas hunt prey in both trees and on the ground. All tarantulas can emit silk, whether they be arboreal or terrestrial species. Arboreal species will typically reside in a silken "tube web", and terrestrial species will line their burrows or lairs with web to catch wandering prey. They mainly eat insects and other arthropods, using ambush as their primary method. The biggest tarantulas can kill animals as large as lizards, mice, or birds. Most tarantulas are harmless to humans, and some species are popular in the exotic pet trade while others are eaten as food. These spiders are found in tropical and desert regions around the world.
The name tarantula comes from the town of Taranto in Italy and was originally used for an unrelated species of European spider. (See Wolf spider for more information about this spider). In Africa, Theraphosids are frequently referred to as "baboon spiders". Asian forms are known as "earth tigers" or "bird spiders". Australians refer to their species as "barking spiders", "whistling spiders," or "bird spiders". People in other parts of the world also apply the general name "mygales" to Theraphosid spiders.
There are other species also referred to as tarantulas outside this family; the evolution of the name Tarantula is discussed below. This article primarily concerns the Theraphosids.
Scorpions are eight-legged arthropods. A member of the Arachnida class and belonging to the order Scorpiones, there are about 2000 species of scorpions. They are found widely distributed south of 49° N, except New Zealand and Antarctica. The northern-most part of the world where scorpions live in the wild is Sheerness on the Isle of Sheppey in the UK, where a small colony of Euscorpius flavicaudis has been resident since the 1860s.
The cuticle makes a tough armor around the body. In some places it is covered with hairs that act like balance organs. An outer layer that makes them fluorescent green under ultraviolet light is called the hyaline layer. Newly molted scorpions do not glow until after their cuticle has hardened. The fluoresent hyaline layer can be intact in fossil rocks that are hundreds of millions of years old.
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