Scorpions

Scorpionida. Spanish: Escorpiones (General), alacranes. Portuguese: Escorpióes, lacraus (Brazil). Nahuatl: Colomeh, sing, cótotl (Mexico).

Scorpions (Polis 1990, Williams 1987) are characterized by their eight legs, a pair of large pinchers or pedipalps (like lobster claws) at the front, and a much smaller but heavy pair of jaws (chelicerae) around the mouth. On the underside, a pair of comblike "pectines" are conspicuous structures. The main body is divided into a large front trunk segment, comprising the head, which is fused with the thorax, and basal abdominal segments. The latter is followed by a long six-segmented tail, the last article of which (the telson) is bulbous and sharp tipped, constituting the sting. The latter contains paired poison glands with ducts opening in a slit a short distance from the tip.

Scorpion sexual behavior is peculiar. The male first faces the female and grasps her pedipalps or chelicerae with his own like appendages. The partners advance and retreat in a kind of dance ("promenade a deux") for a time until a suitable place is found for mating. The male expels a sperm packet to the ground which is picked up by the female's genitalia after more "dancing." Then the female frees herself from the male and goes to a burrow or other shelter; the male goes away. It is not true that the female kills the male. The latter may even live to ultimately mate with several other females.

Females give birth to active larval scorpions. These migrate to their mother's back where they remain until their first molt, when they leave and begin independent lives. In most species, after one to three years and several more molts, they attain adulthood. A rare few of these arachnids lead a semisocial existence (Polis and Lourengo 1986).

Scorpions feed entirely on other arthropods (including other scorpions), mainly spiders and insects that they encounter and overcome during their nightly ram-blings. Certain desert species may go without water for several months but will drink it readily if available; yet scorpions from humid forest environments may die in a few days if forced to go without water.

Scorpion venom produces neurotoxic circulatory and muscular effects in humans. Several species are of major medical importance (Keegan 1980); those in Latin America belong to the genera Tityus and Centruroides, both in the family Buthidae. Tityus (Diniz 1978, Bucherl 1978) are found in varied habitats. Many are humid forest inhabitants, living under the bark of dead trees and among ground litter. They are an entirely Neotropical genus of wide distribution continentally and are present on several of the Antilles. The genus is also the region's largest, with over 130 species (Lourenfo 1978). The deadliest species is T. serrulatus (fig. 4.8a), which causes the demise of many people, especially very young children, in southeastern Brazil. Its venom has been characterized chemically and pharmacologically (Possani et al. 1977).

In the drier parts of Mexico and Central America, species of "bark scorpions" (Centruroides) are the most dangerous (Bucherl 1971, Stahnke 1978); the genus is also found in the West Indies and in parts of South America (Sissom and Louren^o 1987). Among the over fifty species (Santiago-Blay pers. comm., Stanhke and Calos 1977) is the well-known Durango scor

Rflure 4.8 SCORPIONS AND SUN SPIDER, (a) Forest scorpion (Tityus serrulatus, Buthidae). (b) Durango scorpion (Centruroides suffusus, Buthidae). (c) Sun spider (Eremobates sp., Erematobatidae).

pion, C. suffusus (fig. 4.8b) (Atunez 1950), which was responsible for 1,608 deaths between 1890 and 1926 in the city of Du-rango, which had a population of about 40,000 in this period. Actually, the death rate from scorpions is higher in other areas in Mexico, over 110 per hundred thousand in some years in southern states such as Colima (Mazzotti and Bravo-Becherelle 1963).

C. limpidus is an even more potent species and is considered the most dangerous scorpion in Mexico, responsible for more than 50 percent of the 100,000 stings per year in the country (according to Possani et al. [1980], who have also described the qualities of its venom).

From a public health standpoint, scorpions are the most important venomous animals of Mexico. During the period 1940-1949 and 1957-1958, a total of 20,352 persons were killed by scorpion stings (Mazzotti and Bravo-Becherelle 1963).

Small arboreal scorpions are also known in South America. Others, so-called field scorpions, prefer the soil of damp places and are found under stones, especially along rivers. Desert or semidesert types, like Centruroides, are often burrowers in places protected from the heat. Many live in old buildings, under houses, and in garages and often enter occupied premises where they come into contact with humans. True cave-dwelling scorpions are comparatively rare (Francke 1981, Lou-ren?o & Francke 1985, Mitchell 1968). Most scorpions are continental, although a few exist on oceanic or offshore continental islands, such as Coco, the Antilles, and in the Gulf of California.

Overall, in Latin America, there are some 48 genera and more than 400 species allocated to 7 families (Lourengo pers. comm.). The largest genera are Tityus, dominant in South America (Lourengo 1978), and Centruroides, which occurs mostly in Central America and Mexico (Stahnke and Calos 1977). No general taxonomic treatment exists for the entire area, although attempts have been made to review the South American fauna and general distributional patterns (Armas 1982, Lourenço 1986, Mello-Leitäo 1945). A key to the genera of Buthidae is available (Vachon 1977).

References

Atûnez, F. 1950. Los alacranes en el folklore de Durango. Priv. publ., Aguascalientes, Mexico. Bücherl, W. 1971. Classification, biology and venom extraction of scorpions. In W. Bücherl and E. E. Buckley, eds., Venomous animals and their venoms. III. Venomous invertebrates. Academic, New York. Pp. 317-347. Bücherl, W. 1978. Venoms of Tityinae. A. Systematics, distribution, biology, venomous apparatus, etc., of Tityinae; venom collection, toxicity, human accidents and treatment of stings. In S. Bettini, ed., Arthropod venoms. Springer, Berlin. Pp. 371—379. de Armas, L. F. 1982. Algunos aspectos zoogeo-grâficos de la escorpionfauna antillana. Poe-yana 238: 1-17. de Mello-Leitäo, C. 1945. Escorpiöes Sul-Americanos. Mus. Nac. (Rio de Janeiro) Arq. 40: 7-468.

Diniz, C. R. 1978. Venoms of Tityinae. B. Chemical and pharmacologic aspects of Tityine venoms. In S. Bettini, ed., Arthropod venoms. Springer, Berlin. Pp. 379—394. Francke, O. F. 1981. A new genus of troglobitic scorpion from Mexico (Chactidae, Mega-corminae). Amer. Mus. Nat. Hist. Bull. 170: 23-28.

Keegan, H. L. 1980. Scorpions of medical importance. Univ. Mississippi, Jackson. Lourenço, W. R. 1978. Sur les difficultés rencontrées dans la révision du genre Tilyus (Scorpiones, Buthidae). Zool. Soc. London Symp. 42: 502. Lourenço, W. R. 1986. Les modèles de distribution géographique de quelques groupes de scorpions néotropicaux. Soc. Biogeogr. Comp. Rend. 62: 61-83. Lourenço, W. R., and O. F. Francke. 1985. Révision des connaissances sur les scorpions cavernicoles (troglobies) (Arachnida, Scorpions). Mem. Biospél. 12: 3-7. Mazzotti, L., and M. A. Bravo-Becherelle. 1963. Scorpionism in the Mexican republic. In H. L. Keegan and W. V. Macfarlane, eds., Venomous and poisonous animals and noxious plants of the Pacific Region. Macmillan, New York. Pp. 119-131.

Mitchell, W. R. 1968. Typhlochactas, a new genus of eyeless cave scorpions from Mexico (Scorpionidae, Chactidae). Ann. Speleol. 23: 753-777.

Polis, G. A. 1990. The biology of scorpions.

Stanford Univ. Press, Stanford. Polis, G. A., and W. R. Lourenço. 1986. Sociality among scorpions. 10th Cong. Int. Arachnol. (Jaca, Spain) Actas 1: 111-115. Possani, L. D., A. C. Alagôn, P. L. Fletcher, Jr, and B. W. Erickson. 1977. Purification and properties of mammalian toxins from the venom of the Brazilian scorpion Tityvs serrulatus Lutz and Mello. Arch. Biochem. Biophys. 180: 394-403. Possani, L. D., P. L. Fletcher Jr, A. B. C. Alagôn, A. C. Alagôn, andJ. Z.Juliâ. 1980. Purification and characterization of a mammalian toxin from venom of the Mexican scorpion, Centruroides limpidus tecomanus Hoffmann. Toxicon 18: 175-183. Sissom, W. D„ and W. R. Lourenço. 1987. The genus Centruroides in South America (Scorpi-ones, Buthidae). J. Arachnol. 15: 11-28. Stahnke, H. L. 1978. The genus Centruroides (Buthidae) and its venom. In B. Bettini, ed., Arthropod venoms. Springer, Berlin. Pp. 277-307.

Stahnke, H. L., and M. Calos. 1977. A key to the species of the genus Centruroides Marx (Scorpionida: Buthidae). Entomol. News 88: 111-120.

Vachon, M. 1977. Contribution à l'étude des scorpions Buthidae du nouveau monde. I. Complément à la connaissance de Microtityus rickyi Kj.-W. 1956 de l'île de la Trinité. II. Description d'une nouvelle espèce et d'un nouveau genre Mexicains: Darchenia bernadet-tae. III. Clé de determination des genres de Buthidae du nouveau monde. Acta Biol. Venezuelica 9: 283-302. Williams, S. C. 1980. Scorpions of Baja California, Mexico and adjacent islands. Calif. Acad. Sri. Occ. Pap. 135: 1-12. Williams, S. C. 1987. Scorpion bionomics. Ann. Rev. Entomol. 32: 275-295.

sun spiders

Solpugida (= Solifuga). Wind scorpions.

Members of this order are distinguished from other arachnid groups by their huge, forward-projecting, scissorlike chelicerae. The prosoma behind the chelicerae is con stricted, forming a headlike anterior portion. The pedipalps are similar to the walking legs but are elevated when in use and provided with adhesive organs at the tip. Typically, their soft bodies are covered with short, silky pelage. Most are medium-sized (BL 2-4 cm).

Sun spiders prefer warm, arid habitats and are most abundant in the Chilean, Peruvian, and Mexican deserts. Some occur at high elevations in the Andes. At night, they run rapidly over the substratum and occasionally are seen near houses, where they come to catch insects attracted to lights. They spend the daylight hours and winter months in ground burrows of their own making; some burrow in pithy or rotten wood. Although large specimens are aggressive and formidable in appearance, they are without venom-delivering capabilities and are innocuous to humans. They feed on the other ground-dwelling arthropods that they encounter on their nightly wanderings.

Latin American species are almost all found in the two families Ammotrechidae (widespread; 61 species in several genera) and Eremobatidae (far northern Mexico and Baja California; 21 species in two genera) (Muma 1970, 1976). Eremobates (fig. 4.8c) is a major genus. Two species, Amacata penai (Muma 1971) and Syndaesia rnastix (Maury 1980), from the Atacama Desert and western Argentina, respectively, represent the family Daesiidae ( = Amacataidae).

References

Maury, E. A. 1980. Presencia de la family Daesiidae en América del Sur con la descripción de un nuevo género (Solifugae). J. Arachnol. 8: 59-67. Muma, M. H. 1970. A synoptic review of North American, Central American, and West Indian Solpugida (Arthropoda: Arachnida). Arths. Fla. Neighborhood Land Areas 5: 1 — 62.

Muma, M. H. 1971. The solpugids (Arachnida, Solpugida) of Chile, with descriptions of a new family, new genera, and new species. Amer. Mus. Nov. 2476: 1-23. Muma, M. H. 1976. A review of solpugid families with an annotated list of Western Hemisphere solpugids. West. New Mex. Univ., Off. Res. Pub. 2(1): 1-33.

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