blue-green when exposed to certain wavelengths ranges of ultraviolet light such as that produced by a black light, due to fluorescent chemicals such as beta-carboline in the cuticle. Accordingly, a hand-held ultraviolet lamp has long been a standard tool for nocturnal field surveys of these animals. Fluorescence occurs as a result of sclerotization and increases in intensity with each successive instar. This fluorescence may have an active role in the scorpion's ability to detect light. Relationship with humans Stings Scorpion venom serves to kill or paralyze prey rapidly. The stings of many species are uncomfortable, but only 25 species have venom that is deadly to humans. Those species belong to the family Buthidae, including Leiurus quinquestriatus, Hottentotta spp., Centruroides spp., and Androctonus spp. People with allergies are especially at risk; otherwise, first aid is symptomatic, with analgesia. Cases of very high blood pressure are treated with medications that relieve anxiety and relax the blood vessels. Scorpion envenomation with high morbidity and mortality is usually due to either excessive autonomic activity and cardiovascular toxic effects, or neuromuscular toxic effects. Antivenom is the specific treatment for scorpion envenomation combined with supportive measures including vasodilators in patients with cardiovascular toxic effects, and benzodiazepines when there is neuromuscular involvement. Although rare, severe hypersensitivity reactions including anaphylaxis to scorpion antivenin are possible. Scorpion stings are a public health problem, particularly in the tropical and subtropical regions of the Americas, North Africa, the Middle East and India. Around 1.5 million scorpion envenomations occur each year with around 2,600 deaths. Mexico is one of the most affected countries, with the highest biodiversity of scorpions in the world, some 200,000 envenomations per year and at least 300 deaths. Efforts are made to prevent envenomation and to control scorpion populations. Prevention encompasses personal activities such as checking shoes and clothes before putting them on, not walking in bare feet or sandals, and filling in holes and cracks where scorpions might nest. Street lighting reduces scorpion activity. Control may involve the use of insecticides such as pyrethroids, or gathering scorpions manually with the help of ultraviolet lights. Domestic predators of scorpions, such as chickens and turkeys, can help to reduce the risk to a household. Potential medicinal use Scorpion venom is a mixture of neurotoxins; most of these are peptides, chains of amino acids. Many of them interfere with membrane channels that transport sodium, potassium, calcium, or chloride ions. These