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Associations between flies and spiders; bibio-commensalism and dipsoparasitism. Psyche 84: 150-157. Robinson, M. H., and B. C. Robinson. 1980. Thermoregulation in orb-web spiders: New descriptions of thermoregulatory postures and experiments on the effects of posture and coloration. Zool. J. Linnaean Soc. 64: 87-102. Rypstra, A. L. 1981. The effect of klepto-parasitism on prey consumption and web relocation in a Peruvian population of the spider Nephila clavipes. Oikos 37: 179-182. Vasconcellos-Neto, J., and T. M. Lewinsohn. 1984. Discrimination and release of unpalatable butterflies by Nephila clavipes, a Neotropical orb-weaving spider. F.col. Entomol. 9: 337-344.

Spiny Orb Weavers

Araneidae, Gasteracanthinae.

The females of this category of orb weavers (Robinson and Robinson 1980) are hard bodied, and the abdomen bears conspicuous, sharp-tipped spines, either radiating from its periphery (Gasteracanlha) or diverging from the posterior (Micrathena), the latter giving the spider an arrowhead shape. Their abdomens are also colored lavishly in red, yellow, or white. Small dark depressions or pits dot the dorsum as well. The much smaller males have a cylindrical abdomen, lacking conspicuous spines (Chicker-ing 1961). The abdomen of males in the genus Gasteracantha is squarish and much wider than long; in Micrathena, it is longer than wide. The latter is represented by about forty varied species throughout Latin America.

The usual Gasteracantha in the New World is the common cosmopolitan G. cancriformis (fig. 4.3e; Muma 1971), the genus being primarily Oriental. The species is distributed from Mexico to northern Argentina and is recognized by the presence of six spines on the abdomen. A second, poorly known species, G. tetracan-tha, has only four abdominal spines and is restricted to Puerto Rico, the Virgin Islands, and the Bahamas (Levi 1978).

The webs of Gasteracantha are conspicu ous orbs found between the branches of shrubs and even on buildings. They are made in the morning and are usually inclined at an angle. The outer threads are decorated with flocculent tufts of silk.

References

Chickering, A. J. 1961. The genus Micrathena (Araneae, Argiopidae) in Central America. Mus. Comp. Zool. (Harvard Univ.) Bull. 125: 392-470.

Levi, H. W. 1978. The American orb-weaver genera Colphepeira, Micrathena and Gasteracantha north of Mexico (Araneae, Araneidae). Mus. Comp. Zool. (Harvard Univ.) Bull. 148: 417-442.

Muma, M. 1971. Biological and behavioral notes on Gasteracantha caucriformis (Arach-nida, Araneidae). Fia. Entorno!. 54: 345-351. Robinson, M. H., and B. Robinson. 1980. Comparative studies of the courtship and mating behavior of tropical araneid spiders. Pacific Ins. Monogr. 36: 1-218.

Giant Crab Spiders

Heteropodidae (= Sparassidae) and Selenopidae.

Members of these two families are commonly noticed on walls inside and outside of buildings where their large size (leg span 7—12 cm, BL 2—3 cm) and swift, sideways movements attract attention. Members of both families are known for their ability to hide in narrow cracks and crevices by day, emerging at night to catch insects. They may be especially common around exterior house lights to which moths and beetles are attracted (Muma 1953).

Typically, these spiders are very flat, with a compressed carapace and abdomen, the former almost circular or slightly wider than long. They hold their spiny legs out flat to the sides like a crab. Heteropodids have four of the total of eight eyes, selenopids six, arranged in a row along the anterior margin of the carapace.

The huntsman spider (sometimes also called the banana spider, but see Phoneutria above), Heteropoda venatoria, is the best-known species (fig. 4.4a). It is cosmopoli

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