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Scorpion, spiders, ticks and mites are all arthropods. They belong to the Chelicerata, which refers to the structure of the front appendages. Various authors have proposed different classification schemes. These are based inter alia on the form of the sternum, the presence of protuberances on the legs, the morphology of the telson and the number of lateral eyes. The number of trichobothria (small hair-like sensory organs) on the femur of the pedipalps is also used. Thus the Buthidae have a triangular central sternal plate. The other families have a pentagonal sternum. In general it can be said that scorpions with massive claws (Scorpionidae, Chactidae, Diplocentridae, Bothriuridae) are relatively harmless, while the more dangerous species (Buthidae, Vaejovidae) have finer claws. An often heard explanation is that species with massive claws have no difficulty killing their prey, and so do not need powerful venom. Species with thin delicate pedipalps would need extra assistance from powerful venom. It sounds logical, but it is not known if this correct. The colour of the animal is not significant with regard to toxicity. The identification of a scorpion at the species level is a job for specialists. The use of taxonomic keys presumes a good knowledge of the nomenclature, the jargon, the morphology and anatomy of the animals. Drawings are generally diagrams which require some interpretation, for which prior knowledge is necessary. Several species are indistinguishable from one another on morphological grounds. These cryptic species can only be distinguished with chemical or genetic methods.
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