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Tarantulas

Theraphosidae. Spanish: Tarántulas, arañas peludas (General), matacaballos (Mexico, Central America). Portuguese: Tarántulas, caranguejeiras (Brazil). Jupi-Guarani: Nhanduguagá. Mygalomorphs, bird spiders.

This family is renowned for the enormous size of many of its members. The largest are males of Theraphosa labloncLi (fig. 4.2a), which have a leg span as great as 25 centimeters. Specimens are known also with body lengths of 12 centimeters and with anterior femoral diameters up to 8 millimeters (Gerschman de Pikelin and Schiapelli 1966). The bulkier females are less expansive but may weigh 3 ounces (Gertsch 1979). Most species are smaller but are still large by spider standards (leg span 7.5 to 9.5 cm); others are small (less than 3 cm leg span).

Tarantulas are distinguished from other large hairy spiders by their large vertical fangs and legs that have only two claws, instead of the usual three. The equally sized, small eyes are closely grouped on a small tubercle. There are two pairs of large spinnerets.

Because of their formidable size and hairiness, tarantulas are widely regarded with great fear and are believed to be deadly. In spite of these attitudes, these spiders, especially the Mexican red-legged tarantula (Brachypelma smithi) from northwestern Mexico, are imported in large numbers to the United States to please pet fanciers (Hemley 1986). Acanthoscurria, and others, are legitimately feared by Matto Grosso Indians because of their powerful bite (Bücherl 1971: 229), and Hapalopus are known to carry potent venoms (Espinoza 1966). As toxicity to humans of some tarantulas has been documented, all should be given latitude when encountered (Bettini and Brignoli 1978).

While usually shy and retiring, they may become aggressive if threatened. Stories of their jumping abilities may be exaggerated, but some arboreal species are quite capable of leaps of a meter or more over level ground (orig. obs.).

Against humans and enemies, tarantulas use their bite only in defense. They also discourage attack by flicking the hairs of the dorsum of the abdomen with a hind leg. These are urticating and may lodge in the eyes or sensitive nasal membranes of potential predators (Cooke et al. 1973).

Some Neotropical tarantulas produce a snakelike hissing sound by rubbing the surfaces of basal segments of the pedipalps against opposite surfaces of the first legs. Adults of both sexes use this form of stridulation apparently as a protective mechanism; it can be heard up to 6 meters away (Thorns 1983).

These spiders, particularly the females, are long lived. In nature, most probably mature in 5 to 10 years and may live several years thereafter.

The venom is normally used to subdue prey. Their food consists mostly of other ground-dwelling arthropods, although the largest species certainly catch and devour small vertebrates such as frogs, toads, lizards, and nestling or small birds. A famous illustration of a specimen in the act of feeding on a small bird, which appeared in Madame Merian's Metamorphoses Insectorum Surinamensium (1705), is probably responsible for the reputation of these spiders as ornithophages.

There are both terrestrial and arboreal tarantulas (pi. la). The former spend the day in burrows of their own construction or natural retreats in the soil, emerging at night to hunt or seek mates. Tree-dwelling forms hide among epiphytes or in crevices or under the loose bark of dead trees. Others form silken nests in rolled up leaves of terrestrial bromeliads, bananas or Heli-conia, in palm spathes, or in the bristly bases of these leaves.

A bit of folklore prevailing in Mexico and Central America is the legend of the

Figure 4.2 SPIDERS, (a) Tarantula (Theraphosa lablondi, Theraphosidae). (b) Jumping spider (unidentified, Salticidae). (c) Ant-mimicking jumping spider (Aphantochilus sp., Salticidae). (d) Ant model of ant-mimicking jumping spider (Cephalotes sp., Formicidae). (e) Wolf spider (Lycosa raptoria, Lycosidae). (f) Banana spider (Phoneutria fera, Ctenidae).

Figure 4.2 SPIDERS, (a) Tarantula (Theraphosa lablondi, Theraphosidae). (b) Jumping spider (unidentified, Salticidae). (c) Ant-mimicking jumping spider (Aphantochilus sp., Salticidae). (d) Ant model of ant-mimicking jumping spider (Cephalotes sp., Formicidae). (e) Wolf spider (Lycosa raptoria, Lycosidae). (f) Banana spider (Phoneutria fera, Ctenidae).

matacaballo. At one time, many people thought that hoof-and-mouth disease of cattle was caused by tarantulas. The spiders were presumed to hunt sleeping animals and take a narrow strip of hair from above the hoof for its nest building, using an acid secretion to make the hair slough off (a symptom of the disease). The site of the injury suffers infection, and the hoof may be lost. The disease is actually caused by a bacillus; tarantulas line their nests with their own silk (Gertsch 1979: f f7).

The taxonomy of these spiders remains in an unsettled state. Although their higher classification has been organized (Raven 1985), only a few of the major theraphosid groups have received attention internally by modern workers (Schiapelli and Gersch-man de Pikelin 1967, 1979; Gerschman de Pikelin and Schiapelli 1973). Approximately four hundred Latin American species are described, ranging through all climes from deserts to rain forest. They are much fewer and less common at the higher elevations.

References

Bettini, S., and P. M. Brignoli. 1978. Review of the spider families, with notes on the lesser-known poisonous forms. In S. Bettini, ed., Arthropod venoms. Springer, Berlin. Pp. 101-120.

Bucherl, W. 1971. Spiders. In W. Biicherl and E. E. Buckley, eds., Venomous animals and their venoms. 3. Venomous invertebrates. Academic, New York. Pp. 197-277.

Cooke, J. A. L., F. H. Miller, R. W. Grover, and J. L. Duffy. 1973. Urticaria caused by tarantula hairs. Amer. J. Trop. Med. Hyg. 22: 130-133.

Espinoza, N. C. 1966. Acción de veneno de Hapalopus limensis. Inst. Butantan Mem. 33: 799-808.

Gerschman de Pikelin, B. S., and R. D. Schiapelli. 1966. Contribución al conocimiento de Theraphosa lablondi (Latreille), 1801 (Aranea: Theraphosidae). Inst. Butantan Mem. 33: 667-674.

Gerschman de Pikelin, B. S., and R. D. Schiapelli. 1973. La subfamilia Ischnocolinae (Araneae: Theraphosidae). Mus. Argentino Cien. Nat. Bernardino Rivadavia, Insto. Nac. Invest. Cien. Nat. Entomol. Rev. 14: 43-77.

Gertsch, W. J. 1979. American spiders. 2d ed. Van Nostrand Reinhold, New York.

Hemley, G. 1986. Spotlight on the red-kneed tarantula trade. Traffic (U.S.A.) 6(4): 16-17.

Raven, R.J. 1985. The spiderinfraorderMygalo-morphae (Araneae): Cladistics and system-atics. Amer. Mus. Nat. Hist. Bull. 182: 1-180.

Schiapelli, R. D., and B. S. Gerschman de Pikelin. 1967. Estudio sistemático comparativo de los géneros "Theraphosa" Walck., 1805, "Lasiodora" C. L. Koch, 1851 y "Serkopelma Äusserer, 1975 (Aranae, Theraphosidae). Atas Simp. Biota Amazónica 5: 481-494.

Schiapelli, R. D., and B. S. Gerschman de Pikelin. 1979. Las arañas de la subfamilia Theraphosinae (Araneae, Theraphosidae). Mus. Argentino Cien. Nat. Bernardino Riva-divia, Insto. Nac. Invest. Cien. Nat. Entomol. Rev. 5: 287-300.

Thoms, E. 1983. Sound production by a South

American theraphosid. Paper delivered at the annual meeting of the Entomological Society of America, Detroit.

jumping Spiders

Salticidae. Spanish: Papamoscas (Peru).

In spiders of this family, the anterior, median eyes are paired and enormously enlarged and face forward on the steeply elevated anterior portion of the céphalothorax. They afford the animal excellent binocular vision, enabling it to judge distance very well. Two pairs of additional smaller eyes are located behind the principal eyes.

Good eyesight is correlated with oversized forelegs, and short, strong hind legs, all modifications for prey capture by ambush (Forster 1982). Prey is stalked by characteristic jerking, orienting visual movements of the whole body, to within 7 to 15 centimeters distance; then a thread is attached to the substrate and the final distance jumped. The spider may then drop off the substrate on the thread line to isolate the quarry. Extensive webbing is spun only for refuge and protection of the eggs. A wide variety of insects and other arachnids are taken; some salticids attack and subdue victims considerably larger than themselves (Robinson and Valerio 1977). They even pounce on orb spiders situated in the center of their webs.

The males often have extra long chelic-erae and are brightly colored, frequently in polychrome. The patterns of many are complex and resplendent in detail, including iridescent blue and green spots and scale patches. The entire dorsum of the abdomen is often solid, vivid red or orange. Salticids are well known for their eyecatching courtship displays, during which the often elaborately decorated males vigorously posture and dance in front of observant females (fig. 4.2b) (Crane 1949; see Richman 1981 for a bibliography).

Many salticids are ant mimics (Galiano

1967, Reiskind 1977). In addition to having an antlike body, they move their slender forelegs in front of the head like the probing antennae of their models and often have enlarged pedipalps that resemble ant mandibles. In Peru, ants of the genus Cephalotes (fig. 4.2d) are naturally well protected by their heavy armor and spined bodies. They are closely mimicked by spiders of the genus Aphantochilus (fig. 4.2c) which have a narrowed, formicoid waist, black color, and even a spine on the anterior part of the cephalothorax like the ant. The anterior part of the body has a form that looks much the same as the ant's head (Preston-Mafham and Preston-Mafham 1984). There is one apparent case of an ant mimic in symbiosis with the leaf-nesting ant Tapinoma melanocephalum, the spider using the ant's nest for support and perhaps protecting the latter from invading predatory insects (Shepard and Gibson 1972).

Salticidae is a large family with many small genera. The majority of the Neotropical species are probably still unknown.

References

Crane, J. 1949. Comparative biology of salticid spiders at Rancho Grande, Venezuela. Pt. IV. An analysis of display. Zoologica 34: 159-215. Forster, L. 1982. Vision and prey-catching strategies in jumping spiders. Amer. Sei. 70: 165-175.

Galiano, M. EL. 1967. Salticidae (Araneae) formiciformes. VIII. Nuevas descripciones. Physis 27: 27-39. Preston-Mafham, R., and K. Preston-Maf-ham. 1984. Spiders of the world. Facts on File, New York. Reiskind, J. 1977. Ant-mimicry in Panamanian clubionid and salticid spiders (Araneae: Clubionidae, Salticidae). Biotropica 9: 1-8. Richman, D. B. 1981. A bibliography of courtship and agonistic display in salticid spiders. Peckhamia 2: 16-23. Robinson, M. H., and C. E. Valerio. 1977. Attacks on large or heavily defended prey by tropical salticid spiders. Psyche 84: 1 — 10. Shepard, M., and F. Gibson. 1972. Spider ant symbiosis: Continusa spp. (Araneida: Salti-

cidae) and Tapinoma melanocephalum (Hy-menoptera: Formicidae). Can. Entomol. 104: 1951-1954.

Wolf Spiders

Lycosidae. Spanish: Arañas lobos (General), paccha arañas (Peru). Portuguese: Aranhas lobos.

Wolf spiders (Stratton 1985) are varied in size (BL 10-20 mm), hairy, usually dark brown, and fast moving. They attract attention and are much feared, although most are harmless. Large species in the genus Lycosa, however, may bite humans with serious consequences. The venom is cytotoxic and produces great local pain as well as lingering necrotic effects. The spiders are recognized by their moderate hairiness and the three pairs of long, heavy, black spines arming the anterior tibia. The back of the light brown ceplialothorax is often marked with contrasting broad, longitudinal bars or lines.

Lycosids are otherwise of much importance ecologically as controllers of insect populations, especially on the ground, which is their usual haunt. They are vagrant hunters with good vision used in prey capture. Very few build webs; they sit and wait for other spiders and insects that they ambush, usually nocturnally. They can be located at night by the bright reflectance of their eyes in a flashlight beam. A widespread species is Lycosa raptoria (fig. 4.2e).

Many have pronounced aggressive and fighting behaviors as well as highly developed maternal instincts. Females carry egg sacs and spiderlings for some time. Spiny, knobbed hairs on the back of the abdomen apparently provide the stimulus and means of attachment for this form of brood care (Rovner et al. 1973).

References

Rovner, J. S., G. A. Higashi, and R. F. Foelix. 1973. Maternal behavior in wolf spiders:

The role of abdominal hairs. Science 182: 1153-1155.

Stratton, G. E. 1985. Behavioral studies of wolf spiders: A review of recent research. Rev. Arachnol. 6: 57-70.

Banana Spiders

Ctenidae, Cteninae, Phoneutria. Portuguese: Aranhas armadeiras (Brazil). Wandering spiders.

Spiders in the genus Phoeneutria are fairly large (10-12 cm leg span, adult females BL 35-50 mm) and powerfully built. The eight eyes are in three rows (2-4-2), the last two the largest and the two laterals of the second row the smallest. They have a short coat of grayish to pale brown pelage, with larger black spines and chelicerae that are conspicuously clothed with long red hairs. The inner surfaces of the three apical segments of the palpi are heavily fringed with hairs.

These are essentially nocturnal, vagrant spiders, wandering on the ground from evening to dawn in search of prey. They do not construct webs to entrap food. They are also very aggressive and pugnacious, rearing on the hind legs with the two pairs of forelegs raised threateningly and fangs bared (fig. 4.2f). This exposes their undersides, which are strongly darkened on either side of a contrasting pale joint membrane between the basal joint of the first two pairs of legs.

Banana spiders retreat into dark places during the day and frequently enter dwellings where they may hide themselves in clothes or shoes. They are often found among bunches of bananas, which has earned them their vernacular name.

The venom of banana spiders is considered highly toxic, and a few cases of human deaths from their bite are well documented (e.g., Trejos et al. 1971), although this has occurred only in persons who are weak or small children. Bites occur frequently among workers who handle clusters of bananas. Some characteristic symp toms are local intense pain, tachycardia, salivation, disturbed vision, sweating, priapism, and prostration (Schenberg and Pereira Lima 1978).

Two well-known species are P. nigri-venter, from southern Brazil, and P. fera (fig. 4.2f), which inhabits Amazonas.

Equally large but less dangerous spiders in the genus Ctenus are easily confused with banana spiders but differ in the lack of dense hair brush on the inner palpal surfaces (Biicherl et al. 1964).

References

Bucherl, W., S. Lucas, and V. Dessimoni. 1964. Aranhas da familia Ctenidae, Sub-familia Cteninae. I. Redescrifao dos generos Ctenus Walckenaer 1805 e Phoneutria Perty 1833. Inst. Butantan Mem. 31: 95-102. Schenberg, S., and F. A. Perf.ira Lima. 1978. Venoms of Ctenidae. In S. Bettini, ed., Arthropod venoms. Springer, Berlin. Pp. 217-245. Trejos, A., R. Trejos, and R. Zeled6n. 1971. Aracnidismo por Phoneutria en Costa Rica (Araneae: Ctenidae). Rev. Biol. Trop. 19: 241-249.

Typical Orb Web Spiders

Araneidae (= Argiopidae).

This is the most characteristic of the several families that spin orb-shaped webs (like a wagonwheel with a hub, radiating struts and concentric circular ties). Most of the spiders in the family Araneidae are fairly large, often with grossly enlarged and frequently brightly colored abdomens. The lateral eyes are at a distance from the medial, the latter forming a square. They have poor vision and locate prey caught in their webs by feeling the tension and vibration of the threads (Craig 1989). They wrap captives in sheets of silk drawn from the spinnerets by the hind legs. Several members of the family are favorite subjects of behavioral (Robinson and Olazarri 1971, Robinson and Robinson 1980) and ecological study, especially species in the genera Araneus and Argiope (Robinson and Robinson 1978), although there are rela tively few Neotropical species in these primarily Holarctic genera. A widespread, common Latin American araneid is Eustala anistera (fig. 4.3a).

Araneus is the larger and more widespread genus. The female's abdomen is often immense and nearly spherical and many times is marked with complex spotted or variegate patterns. Many species of the genus are nocturnal and thus are seldom seen and appreciated. There are fewer kinds of Argiope, but they are more conspicuous because of large size, bright colors, and diurnal habits (Levi 1968). The females sit head downward with legs oriented like an "X"; they remain in the center of their webs during the day, often flanked above and below by zigzagging sheet silk structures (stabilimenta) in the web (at the tips of the legs in the silver orb weaver). Several species are spread over many parts of the globe, such as the golden orb weaver (A. aurantia), which occurs only in the New World, from Mexico to Guatemala, with an ovoid black abdomen marked by irregular sublateral orange-yellow streaks; the banded orb weaver (A. trifasciata), whose similarly shaped abdomen is white with narrow black rings; and the silver orb weaver (A. argentata) (fig. 4.3c), with a compressed, marginally lobed abdomen that is red, black, and silver spotted posteriorly and solid silver basally like that of the adjoining thorax. The embryology of the last species has been studied by Tse and Tse (1980).

Natural selection has produced many variations on the orb web theme for prey capture. Bolas spiders (Mastophora) (fig. 4.3d), for example, diverge radically from the typical orb weavers in their hunting method, as they do not rely passively on a web to catch prey. Instead, at night, they spin a hanging line with a sticky round globule at the tip. When prey approaches, the spider swings this "bola" and catches it on the globule (Eberhard 1980). The podadora (Mastophora gasteracanthoides) or

Argiopidae Per
Figure 4.3 ORB WEB SPIDERS (ARGIOPIDAE). (a) Common orb weaver (Eustala anistera), female. (b) Golden silk spider (Nephila clavipes), female, (c) Silver orb weaver (Argiope argentata), female, (d) Bolas spider (Mastophora dizzydeani), female, (e) Spiny orb weaver (Gasteracantha cancriformis).

"true bolas spider," a moderate-sized (BL 11 mm), dark brown, slow-moving species with large horns on the abdomen, is known to workers in vineyards in South America who believe it bites with serious effects. It is probable, however, that only its fearsome appearance incriminates it, and some other agent is actually responsible for the lesions suffered by some individuals who encounter it. The bolas structure has been found to contain a volatile substance similar to the sex pheromone of a favored prey, owlet moths of the genus Spodoptem. The male moths are attracted to the vicinity of the spider whose chances of securing a meal are thus greatly enhanced (Eberhard 1977).

References

Craig, C. L. 1989. Alternative foraging modes of orb web weaving spiders. Biotropica 21: 257-264.

Eberhard, W. G. 1977. Aggressive chemical mimicry by a bolas spider. Science 198: 1173-1175.

Eberhard, W. G. 1980. The natural history and behavior of the bolas spider Mastophora dizzydeani sp. n. (Araneidae). Psyche 87: 143-169.

Levi, H. W. 1968. The spider genera Gea and Argiope in America (Araneae: Araneidae). Mus. Comp. Zool. (Harvard Univ.) Bull. 136: 319-352.

Robinson, M. H., and J. Olazarri. 1971. Units of behavior and complex sequences in the predatory behavior of Argiope argentata (Fab-ricius): (Araneae: Araneidae). Smithsonian Contrib. Zool. 65: 1-36. Robinson, M. H., and B. C. Robinson. 1978. Thermoregulation in orb-web spiders: New descriptions of thermoregulatory postures and experiments on the effects of posture and coloration. Zool. J. Linnean Soc. 64: 87-102. Robinson, M. H., and B. C. Robinson. 1980. Comparative studies of the courtship and mating behavior of tropical araneid spiders. Pacific Ins. Monogr. 36: 1-218. Tse, M. do C. P., and H. D. Tse. 1980. Notas sobre o desenvolvimento da aranha Labidog-natha Argiope argentata (Fabricius, 1775) (Araneae, Araneidae). Rev. Brasil. Biol. 40: 249-255.

Golden Silk Spider

Araneidae, Nephilinae, Nephila clavipes. Spanish: Araña de oro (Costa Rica). Golden-web spider, giant orb weaver.

Female Nephila clavipes are very large orb web spiders. It is not unusual to find specimens with a body length of 3 to 4 centimeters and a leg span of 5 centimeters resting head downward in the middle of their gigantic orb-shaped webs (fig. 4.3b). The web may be almost a meter square. Young individuals make a complete web; adults build only the bottom portion. The males are much smaller (BL 1 cm) and remain secreted in foliage at the edge of the web.

The web strands are exceedingly heavy and strong and are shiny gold in color. A perpendicular ladderlike structure (stabili-mentum) of dense, multistranded zigzags is often constructed by a young female above and below her resting place at the hub. The function of this device is not known (Robinson and Robinson 1973). The webs are commonly occupied by other spiders (e.g., Conopistha, Argyrodes) that are not detected or tolerated by the web makers. They are considered kleptoparasites, stealing prey caught in the host's web. Their presence may be responsible for frequent relocation of the host to new web sites (Rypstra 1981). Robinson and Robinson (1977) observed milichiid flies of the genus Phyllomyza living on the céphalothorax of this Nephila in Panama. The flies helped themselves to the juices of the spider's prey after it was wrapped and partially digested.

This is the only Latin American species of its genus, one comprised of several widely distributed species in the Old World tropical lowlands (Lubin 1983, Robinson and Robinson 1980: 34f.). The body is elongate, the abdomen long ovoid and steeply inclined toward the front. The latter is colored olive brown with a double series of lighter, cream-colored spots along the dorsum. The legs are very long and have characteristic thick tufts of black hairs below the joints of the basal segments. The third pair of legs are shorter than the others and lack tufts. Males are similar but much smaller, with a body length of only about 4 to 8 millimeters, and their legs are untufted.

The species prefers sparse to moderate forest vegetation in which it builds its large webs in gaps and corridors where its prey is likely to pass (Moore 1977). If prey is sufficiently abundant, different females Hay build webs contiguous to each other in large aggregations. Prey usually consists of flies, bees, wasps, and small moths and butterflies (Robinson and Mirick 1971).

Females locate their round egg sacs on leaves at the ends of twigs at least 1 meter aboveground (Christenson and Wenzel 1980). Seasonal variation in egg production has been studied by Christenson, Wenzel, and Legum (1979). Spiderlings are communal and feed only on immobile prey, small insects and their own kind (Hill and Christenson 1981).

Recent experiments show that the species discriminates unpalatable butterflies and releases them unharmed from its web. Release is not accidental but results from a behavioral sequence specifically programmed to that end (Vasconcellos-Neto and Lewinsohn 1984).

References

Christenson, T. E., and P. A. Wenzel. 1980. Egg-laying of the golden silk spider, Nephila clavipes L. (Araneae, Araneidae): Functional analysis of the egg sac. J. Anim. Behav. 28: 1110-1118.

Christenson, T. E., P. A. Wenzel, and P. Legum. 1979. Seasonal variation in egg hatching and certain egg parameters of the golden silk spider Nephila clavipes (Araneidae). Psyche 86: 137-147.

Hill, E. M., and T. E. Christenson. 1981. Effects of prey characteristics and web structure on feeding and predatory responses of Nephila clavipes spiderlings. Behav. Ecol. So-ciobiol. 8: 1-5. Lubin, Y. D. 1983. Nephila clavipes (Arana de oro, Golden Orb-spider). In D. H. Janzen, ed., Costa Rican Natural History. Univ. Chicago Press, Chicago. Pp. 745—747. Moore, C. W. 1977. The life cycle, habitat and variation in selected web parameters in the spider, Nephila clavipes Koch (Araneidae). Amer. Midi. Nat. 98: 95-108. Robinson, M. H., and H. Mirick. 1971. The predatory behavior of the golden-web spider Nephila clavipes (Araneae: Araneidae). Psyche 78: 123-139. Robinson, M. H., and B. C. Robinson. 1973. The stabilimenta of Nephila clavipes and the origins of stabilimentum-building in araneids. Psyche 80: 277-288. Robinson, M. H., and B. C. Robinson. 1977.

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