Harvestmen

Opiliones (= Phalangida). Spanish:

Macacos (Mexico).

There is an inordinate diversity of Opiliones in the Neotropical Region (Kaestner 1937), where the majority of the world's approximately 5,000 species are found (Roewer 1923).

There are two dominant groups, the Cyphopalpitores and Laniatores (Martens 1986). The former, typified by the Gag-rellidae, mostly exhibit a small (BL 4—6 mm), simple, oval body suspended in the center of the immensely long, slender (almost filamentous) legs, the second pair of which are usually the longest (fig. 4.4d). The pedipalps are slender with weak claws apically, and the coxae of the legs are separated ventrally by a breast plate. The Laniatores, best known in the Neotropics by the family Gonyleptidae, have relatively shorter legs of varied length and stoutness, the hind pair often longest and heaviest, with very large coxal segments and elaborate spines or other excrescences (fig. 4.4e). The pedipalps are stout, with grasping claws at the tip. The hard body is also often spined, and the coxae of the legs touch along the midline ventrally. Both groups typically possess eight legs and a prosoma divided dor-sally into three parts by two transverse grooves. The abdomen is distinctly segmented and continuous with the prosoma. The three-segmented chelicerae have long blades, and the pedipalps are leglike but always much shorter than the legs.

Most species in this order live in humid retreats, beneath rocks, in tree bark crevices, and in niches on the forest floor. Others roam freely on the ground or on tree trunks or other vegetation. All prefer shade and moist conditions. Their food consists of other small invertebrates (mites, springtails, even snails). Some may take only plant detritus.

Harvestmen protect themselves in a variety of ways (Cokendolpher 1987). They are secretive, often nocturnal, cryptically colored and formed, and practice appen-dotomy (voluntary dropping of legs). When disturbed, they can eject defensive qui-nones and phenols (Roach et al. 1980) from paired repugnatorial glands on the anterior edge of the prosoma. Vonones sayi from Panama initially discharges a clear fluid containing quinones from its glands and the mouth and then dips the tips of its forelegs into the mixture and brushes them against the offending agent (Eisner et al. 1971).

Generally, the sexes meet fortuitously, eggs are laid on moist substrata, and no parental care is exhibited. But the males of at least one species, Zygopachylus albomargi-nis construct and guard a nest of bark detritus on fallen trees which females visit to copulate and lay their eggs (Rodriguez and Guerrero 1976).

The order is little studied in Latin America. Soares and Soares (1948, 1949, 1955) provide a catalog of most of the genera. Ringuelet's (1959) extensive review of the

Argentinian fauna is of general utility. Many taxa are easily recognized by their beautiful coloration and strange body forms.

References

Cokendolpher, J. C. 1987. Observations on the defensive behaviors of a Neotropical Gonylep-tidae (Arachnida, Opiliones). Rev. Arachnol. 7: 59-63.

Eisner, T., A. F. Kluge, J. E. Carrel, and J. Meinwald. 1971. Defense of phalangid: Liquid repellent administered by leg dabbing. Science 173: 650-652. Kaestner, A. 1937. Ordnung der Arachnida: Opiliones Sunderval = Weberknechte. In W. Kühkenthal and T. Krumbach, ed., Handbuch der Zoologie. W. Gruyter & Co., Berlin. Band 3, Hälfte 2, Lief. 9, (2) Teil. Pp. 385-496. Martens, J. 1986. Die Grossgliederung der Opiliones und die Evolution der Ordnung (Arachnida). Actas 10th Cong. Int. Arach. (Jaca, Spain) 1:289-310. Ringuelet, R. A. 1959. Los arácnidos Argentinos del orden Opiliones. Mus. Arg. Cien. Nat. "Bernardino Rivadavia," Inst. Nac. Cien. Nat. Zool. Rev. 5: 127-439, pl. 1-20. Roach, B., T. Eisner, and J. Meinwald. 1980. Defensive substances of opilionids. J. Chem. Ecol. 6: 511-516. Rodríguez T., C. A., and S. Guerrero B., S. 1976. La historia natural y el comportamiento de Zygopachylus albomarginis (Chamberlain) (Arachnida, Opiliones: Gonylep-tidae). Biotropica 8: 242-247. Roewer, C. F. 1923. Die Weberknechte der Erde, systematische Bearbeitung der bisher bekannten opiliones. G. Fischer, Jena. Soares, B. A. M., and H. E. M. Soares. 1948. Monografía dos géneros de Opiliöes Neo-trópicos. Arq. Zool. Säo Paulo 5: 553-635. Soares, B. A. M., and H. E. M. Soares. 1949. Familia Gonyleptidae, continuado. Arq. Zool. Säo Paulo 7: 151-239. Soares, B. A. M., and H. E. M. Soares. 1955. Monografía dos géneros de Opiliöes Neo-trópicos. Arq. Zool. Säo Paulo 8: 225-302.

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