Mites And Ticks

Acari (= Acarina, Acarida).

The mites are the most diverse and species-rich group of arachnids and also the most difficult to characterize (Krantz 1978, Hughes 1959, Flechtmann 1975). Most are very small, some minute (BL 1 to 2 mm). The body is fused into one piece, with no separation between the prosoma and unseg-mented opisthosoma (abdomen), and usually has an ovoid shape, somewhat flattened in most ticks, elongate or quadrate in some mites. The mouthparts extend from a partial, headlike structure anteriorly, formed from fusion of basal pedipalpal and mouth-part segments. The first active stage of development is a "larva" that has six legs.

Once considered a natural group, the mites and ticks are now thought to have multiple origins, and at least three (possibly unrelated) major groups are presently recognized by specialists: Opilioacari-formes (Notostigmata), Parasitiformes, and Acariformes. The first is a primitive assemblage, composed of comparatively large (1 mm or more), elongate, long-legged, leathery mites, somewhat resembling harvestmen (Hoffmann and Vázquez 1986). The second are medium-sized to large, well sclerotized, and with a tracheal system, opening through paired ventrolateral spiracles (stigmata). Many of these are parasitic, including the atypical ticks. The Acariformes are mostly small and have a poorly formed tracheal system, and the body is often divided into two regions by a transverse furrow. Within each category, major subgroupings are recognized according to the presence or absence and position of the stigmata: hidden (Cryptostigmata), anterior (Prostig-mata), between the second and fourth coxae (Mesostigmata), near the posterior coxae (Metastigmata), dorsally (Notostigmata), or absent (Astigmata).

All these groups are well represented in Latin America (Schuster 1969). The fauna is immense, and though many thousands of species are now known, these are surely only a fraction of those that must exist. Anything approaching even a general review is well beyond the scope of this book.

Only a very few of the better-known types of special importance ecologically or economically in the American tropics can be treated here.

All biotic types are represented among mites. There are free-living and parasitic forms on animals and plants. Many parasitic forms are vectors of diseases (Oldfield 1970). Free-living forms dwell in the soil and on vegetation where they feed on sap and tissue fluids, sometimes causing considerable damage to crops (Jeppson et al. 1975). Some cause galls (Eriophyidae), and a few infest flour and other stored grain products.

There are many parasites of vertebrates, including humans. They may be of considerable medical and veterinary importance (Baker et al. 1956, Flechtmann 1973). Most are external biters (Dermanyssus), but a few burrow into the skin (scabies mite) or lodge deep in body cavities (nasal chiggers) or skin pores (hair follicle mite). They are often highly allergenic. Pneumonyssus (Hala-rachnidae) and members of other families infest the lungs and respiratory tracts of snakes and birds. Many are specific ectoparasites of bats (e.g., Chirodiscidae, Chirorhynchobiidae, Spelaeorhynchidae, Spinturnicidae) and other characteristic Neotropical mammals, such as Archemyobia latipilis in opossums (Fain et al. 1981). Pollen- and nectar-feeding species of Rhi-noseius and Proctolaelaps (Ascidae) are phoretic on hummingbirds, living in the nares and using them for transportation from flower to flower (Colwell 1979). The ticks are highly modified bloodsuckers on all vertebrate orders.

Other mites live in bird and mammal nests, scavenging on the host's food or organic detritus therein. Such is Hypoaspis dasypus, known only from armadillo burrows (Menzies and Strandtmann 1952).

Many are associates of other arthropods (Bischoff de Alzuet 1978, Mauri and Bischoff de Alzuet 1972) in various ways, as parasites, predators, and consumers of exudates from the host. Others practice phoresy, using the host for transport only. Some of the better-known examples of the latter are Macrocheles, which are often very numerous on the bodies of dung beetles (Evans and Hyatt 1963). Mites of diverse groups lodge in the tympanic cavities of moths (Treat 1975). Several kinds of mites are also associated with stingless bees (Flechtmann and de Camargo 1974). The varroa mite (Varroa jacobsonii), a notorious apicultural pest in the Old World and now established in all major beekeeping areas in South America, is associated with the honeybee. Arrehenurus is a widespread aquatic genus, ectoparasitic on mosquito larvae and pupae.

Entire families, for example, Analgidae, Cheyletidae, Dermoglyphidae, are adapted to life on the feathers of birds (Gaud and Atyeo 1979). Ophiomegistus (Antennophori-dae) are found on snakes and lizards. Iguanacarus (Trombiculidae) lives in the nasal fossae of the marine iguana of the Galápagos Islands (Vercammen-Grandjean 1965).

Some major groups are aquatic, such as the primarily marine superfamilies Hala-caroidea and freshwater Hydrachnoidea (Cook 1980). The latter can be very abundant in tropical ponds and lakes where they form a part of the plankton community (Gliwicz and Biesiadka 1975).

References

Baker, E. W., T. M. Evans, D. J. Gould, W. B. Hull, and H. L. Keegan. 1956. A manual of parasitic mites of medical or economic importance. Nat. Pest Contr. Assoc. Tech. Publ. Bischoff de Alzuf.t, A. 1978. Ácaros asociados a artrópodos de interés sanitario. Neotropica 24:145-149. Colwell, R. K. 1979. The geographic ecology of hummingbird flower mites in relation to their host plants and carriers. Rec. Adv. Acarol. 2: 461-468. Cook, D. R. 1980. Studies on Neotropical water mites. Amer. Entomol. Inst. Mem. 31: 1-645. Evans, G. O., and K. H. Hvatt. 1963. Mites of the genus Macrocheles Latr. (Mesostigmata)

associated with coprid beetles in the collection of the British Museum (Natural History). Brit. Mus. Nat. Hist. Bull. 9: 327-401. Fain, A., E. Méndez, and F. S. Lukoschus. 1981. Archemyobia (Nearchemyobia) latipilis sp. n. (Acari: Prostigma: Myobiiidae) parasitic on marsupials in Panama and Brazil. Rev. Biol. Trop. 29: 77-81. Flechtmann, C. H. W. 1973. Ácaros de importancia médico-veterinária. Liv. Nobel, Säo Paulo.

Flechtmann, C. H. W. 1975. Elementos de

Acarologia. Liv. Nobel, Säo Paulo. Flechtmann, C. H. W., and C. A. de Camargo.

1974. Acari associated with stingless bees (Meliponidae, Hymenoptera) from Brazil. 4th Int. Cong. Acarol. Proc. Pp. 315-319.

Gaud, J., and W. T. Atyeo. 1979. Co-évolution des acariens sarcoptiformes plumicoles et de leurs hötes. Acarologia 21: 291-306. Gliwicz, Z. M., and E. Biesiadka. 1975. Pelagic water mites (Hydracarina) and their effect on the plankton community in a Neotropical man-made lake. Arch. Hydrobiol. 76: 65-88. Hoffmann, A., and M. Vázquez. 1986. Los primitivos ácaros Opilioacáridos en México. Fol. Entomol. Méx. 67: 53—60. Hughes, T. F.. 1959. Mites or the acari.

Athlone, Univ. London, London. Jeppson, L. R., H. H. Keifer, and E. W. Baker.

1975. Mites injurious to economic plants. Univ. California, Berkeley.

Krantz, G. W. 1978. A manual of acarology. 2d ed. Ore. St. Univ. Bookstores, Corvallis. Mauri, R., and A. Bischoff de Alzuet. 1972. Ácaros asociados a artrópodos. Soc. Argentina Entomol. Rev. 34: 151-159. Menzies, G. C., and R. W. Strandtmann. 1952. A new species of mite taken from nest of armadillo. Entomol. Soc. Wash. Proc. 54: 265-269.

Oldfield, G. N. 1970. Mite transmission of plant viruses. Ann. Rev. Entomol. 15: 343—380. Schuster, R. 1969. Die terrestrische Milbenfauna Südamerikas in zoogeographischer Sicht. In E. J. Fittkau, J. lilies, H. Klinge, G. H. Schwabe, and H. Sioli, eds., Biogeog-raphy and ecology in South America. 2: 741-763. Junk, The Hague. Treat, A. E. 1975. Mites of moths and butterflies. Cornell Univ., Ithaca. Vercammen-Grandjean, P. H. 1965. Iguana-earns, a new subgenus of chigger mite from nasal fossae of the marine iguana in the Galápagos Islands, with a revision of the genus Vatacarus Southcott (Acariña, Trombiculidae). Acarologia 7 (suppl.): 266-274.

Eriophyids

Eriophyidae. Spanish: Eriofidos (General), acaros de agallas. Gall mites.

These mites are marked by structural simplification: they are wormlike and so small as to be barely visible to the unaided eye (BL 0.2 mm); only the anterior two pairs of legs are developed; a tracheal system is absent, and respiration is by cutaneous diffusion. The cuticle bears conspicuous fine rings over the whole body.

All species of eriophyids are obligate plant feeders and constitute the main family of mites injurious to cultivated plants. Physical damage is caused by mechanical feeding and inoculation of harmful viruses. Host responses to feeding are leaf curling and adventitious tissue formation, including twigs, blisters, and galls.

A serious and widespread pest species is the citrus bud mite (Eriophyes [= Aceria] sheldoni) (fig. 4.5a). It is known in all citrus-growing areas of Central and South America. The species infests the bud, developing blossoms, and area beneath the button of citrus fruits as well as leaf axil buds. The growing tissue may be completely destroyed or altered to form stunted or misshapen structures, especially in the fruit, which may assume grotesque shapes, becoming unfit for market.

Another very injurious species is the coconut mite (Eriophyes guerreronis) (Moore and Alexander 1987). Populations develop under the bracts, where their feeding causes scarring on the nuts, leading to reduced copra yields.

Reference

Moore, D., and L. Alexander 1987. Aspects of migration and colonization of the coconut palm by the coconut mite, Eriophyes guerreronis (Keifer) (Acari: Eriophyidae). Bull. Entomol. Res. 77: 641-650.

House Dust Mites

Pyroglyphidae, Dermatophagoides.

House dust, consisting of human and pet skin particles, food fragments, hair, cotton, paper, wool and synthetic fibers, soil, and like material, provides food and shelter for a community of exceedingly minute organisms dominated by arthropods, including many kinds of mites, and fungi (Van Bronswijk 1979, 1981). Among the latter are most commonly the house dust mites of the genus Dermatophagoides, which is represented in Latin America by both the widespread species D.farinae (fig. 4.5b) and the localized D. pteronyssinus. D. neotropicalis is a species sometimes also considered a part of this complex (Fain and Van Bronswijk 1973). As many as 3,000 such mites may inhabit a gram of dust (Arlian et al. 1979). They are more common in the dust on mattresses and bedroom floors than elsewhere in the house.

Dust has long been known to cause allergies and asthma in sensitive persons.

Figure 4.5 MITES, (a) Citrus bud mite (Eriophyes sheldoni, Eriophyidae). (b) American house dust mite (Dermatophagoides farinae, Pyroglyphidae). (c) Spider mite (Tetranychus telarius, Tetrany-chidae). (d) Mold mite (Tyrophagus putrescentiae, Acaridae). (e) Soil mite (Oribatula minuta, Ofibatulidae). (f) Follicle mite (Demodex folliculorum, Demodicidae).

Figure 4.5 MITES, (a) Citrus bud mite (Eriophyes sheldoni, Eriophyidae). (b) American house dust mite (Dermatophagoides farinae, Pyroglyphidae). (c) Spider mite (Tetranychus telarius, Tetrany-chidae). (d) Mold mite (Tyrophagus putrescentiae, Acaridae). (e) Soil mite (Oribatula minuta, Ofibatulidae). (f) Follicle mite (Demodex folliculorum, Demodicidae).

Numerous studies have reported a correlation between symptoms and the presence of house dust mites, although a direct relationship is not yet clearly established (Leeks 1973). What little has been done on these mites and their effect on health in Latin America has centered in Colombia (Mulla and Sánchez Medina 1980, Charlet et al. 1979) and Chile (Casanueva and Artigas 1985).

References

Arlian, L. G., 1. L. Bernstein, C. L.Johnston, and J. S. Gallagher 1979. Ecology of house dust mites and dust allergy. Rec. Adv. Acarol. 2: 185-195.

Casanueva, M. E., and J. N. Artigas. 1985. Distribución geográfica y estacional de los ácaros del polvo de habitación en Chile. Cayana. Zool. 49: 3-75. Charlet, L. D., M. S. Mulla, M. Sanchf.z-Medina, and M. A. Reyes. 1979. Species composition and population trends of mites in various climatic zones of Colombia. J. Asthma Res. 16: 131-148. Fain, A., and J. E. M. H. Van Bronswijk. 1973. On a new species of Dermaluphagoides (D. neolropicalis) from house dust, producing both normal and heteromorphic males (Sar-coptiformes: Pyroglyphidae). Acarologia 15: 181-187.

Lecks, H. 1. 1973. The mite and house dust allergy: A review of current knowledge and its clinical significance. Clin. Pediat. 12: 514— 517.

Mulla, M. S., and M. Sánchez-Medina, ed. 1980. Domestic acari of Colombia, bionomics, ecology and distribution of allergenic mites, their role in allergic disease. COLCIENC1AS, Bogotá.

Van Bronswijk, J. E. M. H. 1979. House dust as an ecosystem. Rev. Adv. Acarol. 2: 167-172. Van Bronswijk, J. E. M. H. 1981. House dust biology for allergists, acarologists, and mycologists. NIB Publ., Zeist, The Netherlands.

Spider Mites

Acarida, Tetranychidae. Spanish: Arañitas, arañas rojas (General). Portuguese: Ácaros de teia, ácaros rajados, ácaros vermelhos (Brazil).

These mites often live amid masses of fine silk webbing on the undersides of leaves which they spin from glands located in the prosoma, a habit earning them their vernacular name (Baker 1979, Helle and Sabelis 1985). The feeding of large numbers of these mites on commercial plants often causes severe damage. Leaves develop pale blotches and may eventually totally dry up. Plants lose their vigor and die (Huffaker et al. 1969). Consequently, many species are recognized pests in Latin America (Pritchard and Baker 1955). Second to the eriophyids, they are probably the most agriculturally important plant-feeding group of mites. A complex of species, the two-spotted spider mite group (Tetranychus bimaculatus, T. telarius [fig. 4.5c], and T. cinnabarinus) is especially troublesome to cotton, beans, and vegetable crops in general, as well as to flowers, especially in greenhouses (Vereau et al. 1978).

Spider mites are green, yellow, orange, or red and small (BL always less than 1 mm), often with dark blotches on either side of the dorsum.

References

Baker, E. W. 1979. Spider mites revisited—a review. Rec. Adv. Acarol. 2: 387-394. Hellf., W., and M. W. Sabelis, eds. 1985. Spider mites: Their biology, natural enemies and control. Vol. 1, Pt. A, 405; Pt. B, 458. Elsevier, Amsterdam. Huffakf.r, C. B., J. A. McMurtry, and M. van de Vrie. 1969. The ecology of tetranychid mites and their natural control. Ann. Rev. Entomol. 14: 125-174. Pritchard, A. E., and E. W. Baker 1955. A revision of the spider mite family Tetranychidae. Pac. Coast Entomol. Soc. Mem. 2: 1-472.

Vf.rf.au, W. V., M. Cueva, and D. Ojeda. 1978. Biologia de la "aranita roja del algodonero" Tetranychus cinnabarinus (Boisduval) (Acarina, Tetranychidae). Rev. Peruana Entomol. 21: 50-54.

Stored Product Mites

Acariformes, various families, including Acaridae and Carpoglyphidae.

Quite a number of mite species are associated with stored food and fiber prod ucts, feeding directly on the substance or secondarily on fungi growing on it. A few are parasitoids of insects living on the substratum.

They are all very small mites (BL mostly 1 mm or less), pale and with long body setae. They may develop enormous populations and be very destructive both in industrial (warehouses, granaries, holds of ships) and household (larders, cupboards, medicine chests) environments. They may literally replace the substratum with the mass of their collective bodies. Some are known to bite humans working around stored products, causing minor rashes ("baker's itch").

The principal of fending species in Latin America belonging to this category are Tyrophagus putrescentiae (Acaridae) (fig. 4.5d), Carpoglyphus lactis (Carpoglyphidae), and Pyernotes ventricosus (Pyemotidae).

Reference

Flechtmann, C. H. W. 1983. Acaros de im-portáncia agrícola. Liv. Nobel, Sao Paulo.

Soil Mites

Oribatuladdae (= Cryptostigmata). Moss mites, beetle mites.

Soil mites (Balogh 1988) form a very large and complex group, comprised of many families and about 450 species as presently known in South America, far short of the probable actual number. Balogh (1972) lists about 270 Neotropical genera, including cosmopolitan and pan-tropical taxa. These mites are very adaptable to environmental stresses and represent one of the few types of terrestrial arthropods surviving on the harsh fringes of Antarctica and the most southerly Atlantic islands (Wall-work 1965). By their very numbers, they play an important role in the decomposition of organic substances in the soil (Williams 1941; see special habitats, chap. 2).

Soil mites, such as the common Oribatula minuta (fig. 4.5e), are generally very well sclerotized, dark-pigmented, hard-bodied mites, most with a body length of less than 1 millimeter. Some have enlarged mouth-parts, and they often have hinged, winglike structures extending from the sides of the body under which they can tuck their legs to form a compact ball for protection. The leg segments are sometimes swollen, giving the legs a nodular appearance.

References

Balogh, J. 1972. The oribatid genera of the world. Akademiai Kiado, Budapest. Balogh, J. 1988. Oribatid mites of the Neotropical Region. 1. The soil mites of the world. Vol. 2. Wallwork, J. A. 1965. The Cryptostigmata (Acari) of Antarctica with special reference to the Antarctic Peninsula and South Shetland Islands. Pacific Ins. 7: 453-468. Williams, E. C. 1941. An ecological study of the floor fauna of the Panamanian rain forest. Chicago Acad. Sci. Bull. 6: 63-124.

Follicle Mites

Demodicidae, Demodex. Portuguese: Cravos (Brazil).

These mites (Desch and Nutting 1971) are all ectoparasites of mammals and remarkably modified for residence in pits in the skin; rarely, they secondarily invade the lymphatic and circulatory system.

They seem to be rigidly host specific (Nutting 1974), certain species being known from several Latin American animals, including the domestic horse (Dernodex equi), dog (D. canis), sheep (D. ovis), pig (D. phylloides), goat (D. caprae), cat (D. cati), and cow (D. bovis). More species are being discovered in wild mammals as well, for example, guinea pigs, mice, monkeys (Lebel and Nutting 1973), and bats (Desch and Nutting 1972). The entire life cycle is spent on the host, all stages being found in skin pustules and hair follicles on the body, especially about the face (Quintero 1978). Transfer to a new host normally requires close contact, possibly in infancy or in the nest.

Humans also harbor a particular species,

D. folliculorum (fig. 4.5f). These are minute (BL 0.1—0.4 mm), with an elongate, almost wormlike body. The opisthosoma is transversely striated. The legs are short and stubby without setae and are located close together anteriorly (Desch and Nutting 1977). The mite inhabits the hair follicles and sebaceous glands, particularly around the nose and eyelids but sometimes elsewhere, such as the scalp. Its presence is usually innocuous but has been known to induce acnelike conditions. It is surprisingly common; probably the majority of the human population anywhere unknowingly serves as host to this species.

In animals, severe symptoms can develop when the mites interfere with secretion and when they invade the skin and bloodstream (Nutting 1975).

References

Desch, D. E., and W. B. Nutting. 1971. Demodicids (Trombidiformes: Demodicidae) of medical and veterinary importance. 3d Int. Cong. Acarol. Proc. Pp. 499-505. Desch, D. E., and W. B. Nutting. 1972. Parasitic mites of Surinam. VII: Dernodex longissi-mus n. sp. from Carollia perspicillata and D. rnolossi n. sp. from Molossus molossus (Demodicidae: Trombidiformes); Meibomian complex inhabitants of Neotropical bats (Chi-roptera). Acarologia 14: 35—53. Desch, C. E., and W. B. Nutting. 1977. Morphology and functional anatomy of Dernodex folliculorum (Simon) of man. Acarologia 19: 422-462.

Demodectic mites of subhuman primates. I: Dernodex saimirí sp. n. (Acari: Demodicidae) from the squirrel monkey, Saimirí sciureus. J. Parasit. 59: 719-922. Nutting, W. B. 1974. Synhospitaly and specia-tion in the Decodicidae [sic] (Trombidiformes). 4th Int. Cong. Acarol. Proc. Pp. 267-272.

Nutting, W. B. 1976. Pathogenesis associated with hair follicle mites (Acari: Demodicidae). Acarologia 17: 493-506. Quintero, M. T. 1978. Frecuencia de ácaros en especies de animales domésticos. Vet. Méx. 9: 111-114.

Scabies Mite

Sarcoptidae, Sarcoptes scabiei. Spanish: Acaro de la sarna. Portuguese: Acariano da sarna (Brazil).

There are several strains or subspecies of this mite (Mellanby 1943, 1985), adapted to different mammal hosts (horses, dogs, pigs, sheep, cattle) including humans, in which it can cause a general skin affliction called scabies or mange (Arlian 1989, Gordon and Unsworth 1947). The species spends its entire life cycle on the host. Females are the infective stage. They lay their eggs in tunnels made by burrowing through the subcutaneous layers of the skin. The adults live a month or more.

The burrowing and feeding (on blood) of the mites of all stages cause extreme itching. The sinuous tunnels are near the skin's surface and can be seen as delicate gray lines, on humans usually between the

Eutrombicula Morphology

Figure 4.6 MITES AND TICKS, (a) Scabies mite (Sarcoptes scabiei, Sarcoptidae), female, (b) Common, or "sweet potato" chigger (Eutrombicula batatas, Trombiculidae). (c) cayenne tick (Amblyomma cajennense, Ixodidae), male, (d) Tropical horse tick (Dermacentor nitens, Ixodidae), male, (e) Fowl tick (Argas miniatus, Argasidae).

Figure 4.6 MITES AND TICKS, (a) Scabies mite (Sarcoptes scabiei, Sarcoptidae), female, (b) Common, or "sweet potato" chigger (Eutrombicula batatas, Trombiculidae). (c) cayenne tick (Amblyomma cajennense, Ixodidae), male, (d) Tropical horse tick (Dermacentor nitens, Ixodidae), male, (e) Fowl tick (Argas miniatus, Argasidae).

fingers and toes, behind the knee, and on the genitalia. Pimples or vesicles may form on the affected skin which when scratched, become infected and cause sores and scabs. Animals may develop large areas of leathery encrustments and lose most of their body hair (mange, sarna pira).

These are very small mites (females 0.4 mm in diameter, males 0.2 mm). They are rotund with very short, stubby legs. The third pair in the male and the third and fourth pairs in the female (fig. 4.6a) are tipped with a very long bristle; the other legs are tipped with small, stalked suckers. The integument is coarsely striated and bears spinelike projections of two sizes on the posterior half of the dorsum.

The species is cosmopolitan in distribution. Infestations spread through close contact between infected hosts. Sarcoptic mange in livestock causes reduction in meat, milk, and wool production and even the death of severely afflicted animals.

References

Arlian, L. G. 1989. Biology, host relations, and epidemiology of Sarcoptes scabiei. Ann. Rev. Entomol. 34: 139-161. Gordon, R. M., and K. Unsworth. 1947. A review of scabies since 1939. Carib. Med. J. 9: 56-71.

Mellanby, K. 1943. Scabies. Oxford Univ.

Press, London. Mellanby, K. 1985. Biology of the parasite [scabies mite]. In M. Orkin and H. 1. Maibach, eds., Cutaneous infestations and insect bites. Marcel Dekker, New York. Pp. 9-18.

Chiggers

Trombiculidae, Eutrombicula. Spanish: Coloradillos, bichos colorados (General); patatas (Surinam); callo-callo, isangos (Peru); celembas (Ecuador). Nahuatl: Tlalzahuatl (Mexico). Portuguese: Bichos colorados. Tupi-Guarani: Micuims (Brazil). French: Bêtes rouges (Cayenne). Harvest mites, red bugs, red mites.

Worldwide, various genera of the family Trombiculidae are the infamous biting mites known as chiggers (Sasa 1961, Wharton and Fuller 1952). Among the eighty-seven genera in America (Brennan and Goff 1977, 1978), the main offender is Eutrombicula, whose larvae attach to humans, causing severe, itching rashes (trom-bidiosis) and other allergenic reactions. Parascoschoengastia (Euschoengastia) nunezi has been responsible for dermatosis in Mexico (Andrade 1947).

In the normal life cycle, the larvae feed on mammals, birds, or reptiles (Wrenn and Loomis 1984). After engorging, they drop off permanently to continue development as free-living, predaceous terrestrial mites (nymphs and adults). The adults are fairly large (BL 2—3 mm), frequently bright red or orange, and covered with a velvety pelage of feathery hairs. They are usually found just beneath the surface of loose soil, in cracks, burrows, leaf litter, humus, or decaying wood where they feed on the eggs and early stages of other minute arthropods, such as springtails.

Structurally, the six-legged larval chiggers are recognizable under high magnification by a pair of unique knobbed or plumose hairs arising from a rectangular plate on the anterior-dorsal surface of the body (idiosoma; Goff et al. 1982, Wharton et al. 1951). The mouthparts consist of a pair of heavy piercing chelicerae and a pair of palpi, which together give the appearance of a head. Contrary to popular belief, the chigger does not burrow into the skin or imbed even this false head. Only the tips of the medial mouthpart elements are inserted. The salivary secretions contain powerful histolytic enzymes that break down deep epithelial cells. The tissue hardens around the chelicerae, forming a feeding canal (stylostome), through which the host's dissolved cells and lymph are siphoned (Allred 1954). After the chigger departs, it is the persistence of this foreign object that produces the long-lasting itching and irritation so characteristic of its bite.

There are nearly eighty species of

Eutrombicula in Latin America (Loomis and Wrenn 1984, Hoffmann 1970). Only a few are regular human pests, and these normally attack lizards, snakes, ground-dwelling birds, or mammals. Species of other genera with regular mammal hosts seem rarely to cause an allergic reaction when they do attach to man. None transmit pathogenic organisms. However, Leptotrom-bidium, known vectors of rickettsioses elsewhere, and Pseudoschoengastia can cause dermatosis and are potentially troublesome.

The most common chiggers attacking humans throughout America belong to the Eutrombicula alfreddugesi group, comprised of several poorly distinguished species (Williams 1946). Their larvae are abundant in transition areas between forest and grassland, along swamp margins, and from sea level to nearly 3000 meters elevation. They normally parasitize almost any terrestrial vertebrate and readily transfer to man.

Another widespread species of major medical importance throughout Latin America is the so-called sweet potato chigger, Eutrombicula batatas (fig. 4.6b) (Michener 1946). This is an animal of sunlit places, the unfed larvae emerging onto the surface of the soil sometimes in large numbers, especially in grassy areas. It may become very abundant around homes and villages where domestic animals, particularly chickens (Canfalonieri and de Carvalho 1973), are numerous. The normal hosts are principally birds and small terrestrial mammals.

References

Allred, D. M. 1954. Observations on the stylostome (feeding tube) of some Utah chiggers. Utah Acad. Sci. Arts & Letters Proc. 31: 61-63.

Andrade, R. M. 1947. Trombididiasis por Neo-schdngastia nunezi Hoffmann, 1944. Gaceta Med. (Mexico) 77: 219-240. Brennan, J. M., and M. L. Goff. 1977. Keys to the genera of chiggers of the Western Hemisphere (Acarina: Trombiculidae). J. Parasitol. 63:554-566.

Brf.nnan, J. M., and M. L. Goff, 1978. Three new monotypic genera of chiggers (Acari: Trombiculidae) from South America. J. Med. Entomol. 14: 541-544.

Canfalonieri, U. E. C., and L. P. de Carvalho. 1973. Ocorréncia de Trombicula (Eutrombicula) batatas (L.) em Galius gallus domesticus L. no estado do Rio de Janeiro (Acarina, Trombiculidae). Rev. Brasil. Biol. 33: 7-10.

Goff, M. L., R. B. Loomis, W. C. Welbourn, and W.J. Wrenn. 1982. A glossary of chigger terminology (Acari: Trombiculidae). J. Med. Entomol. 19: 221-238.

Hoffmann, A. M. 1970. Estudio monográfico de los trombicúlidos de México (Acarina: Trombiculidae). Primera parte. Esc. Nac. Cien. Biol. México An. 18: 191-263.

Loomis, R. B., and W. J. Wrenn. 1984. System-atics of the pesi chigger genus Eutrombicula (Acari: Trombiculidae). Acarology 6(1): 152-159.

Michener, C. D. 1946. Observations on the habits and life history of a chigger mite, Eutrombicula batatas (Acarina: Trombiculidae). Entomol. Soc. Amer. Ann. 39: 101-118.

Sasa, M. 1961. Biology of chiggers. Ann. Rev. Entomol. 6: 221-244.

Wharton, G. W., and H. S. Fuller. 1952. A manual of the chiggers. Entomol. Soc. Wash. Mem. 4: 1-185.

Wharton, G. W., D. W.Jenkins,J. M. Brf.nnan, H. S. Fuller, G. M. Kohls, and C. B. Phillip. 1951. The terminology and classification of trombiculid mites (Acarina: Trombiculidae). J. Parasitol. 37: 13-31.

Williams, R. W. 1946. A contribution to our knowledge of the bionomics of the common North American chigger, Eutrombicula alfreddugesi (Oudemans), with a description of a rapid collecting method. Amer. J. Trop. Med. 26: 243-250.

Wrenn, W. J., and R. B. Loomis. 1984. Host selectivity in the genus Eutrombicula (Acari: Trombiculidae). Acarology 6(1): 160—165.

Ticks

Ixodoidea. Spanish: Garrapatas (General); conchudas, plateadas, pinolillos (Mexico). Portuguese: Carrapatos, carrapatos pólvoras, carrapatos fogo, carrapatinhos (Brazil-larvae). Nahuatl: Mazaatemimeh, sing, mazaatémitl (Mexico).

Ticks comprise an isolated and very specialized group of mites distinguished by well-

developed, multifaceted spiracles situated lateral to the third coxae or behind the fourth coxae (Obenchain and Galun 1982, Oliver 1989). The integument is leathery to hard, and they are all considerably larger than most mites (BL 2—5 mm). Their mouthparts are unique: the digits of the chelicerae have lateral teeth, and between the pedipalps is a median holdfast organ with recurved teeth (called the hypostome). The first tarsus has a dorsal heat-sensitive organ in a large pit (Haller's organ) to assist in finding vertebrate hosts on which they feed. Ticks anchor onto the host's skin by the hypostome and do not drop off until they finish feeding. If forcibly removed, the hypostome (erroneously thought to be the head by most people) may remain in the wound and fester.

After molting, ticks wait on the tips of twigs or leaves, forelegs outstretched and ready to snag any animal brushing past. On the potential host's approach, the legs wave frantically in response to various stimuli: primarily to carbon dioxide exhaled during respiration but also to vibration, body heat, or the host's shadow passing over them.

Two main families of ticks are recognized, the "hard ticks" (Ixodidae) and "soft ticks" (Argasidae). Hard ticks are flattened, and all stages bear a thick, tough plate (scutum) dorsally. This plate covers only about half the anterior end of the body in larvae, nymphs, and females; the entire body in males. It may or may not be ornamented with silver. Soft ticks are baglike, without plates in postlarval stages. The mouthparts are hidden by the overhanging body (camerostoma). They are primarily nest inhabitants and parasites of birds and small mammals (mainly bats) in semitropical and tropical areas. They are very resistant to water loss and are characteristic of desert faunas.

Ticks are ectoparasitic in all stages, feed-•ng primarily on the blood of mammals, birds, reptiles, and amphibians. Usually, individuals attach to different host species in their various stages (larva, nymph, adult) and feed only once on each. Some, however, remain on a single host throughout their lifetime. The body, especially that of the female, is elastic and capable of enormous distension when the stomach fills with blood or eggs. Specimens may reach the size of a grape after 5 to 6 days of feeding. Adult males of some species apparently do not feed at all.

There are many more ixodid than argasid species (114 and 58, respectively) in the Neotropics (Keirans pers. comm.). The genera are Ixodes, Dermacentor (including Anocenter; Yunker et al. 1986), Haemaphy-salis, Boophilus, Amblyomnia, Rhipicephalus, and Aponomma.

Several hard tick species are of special importance. The southern cattle tick (Boophilus microplus) is prevalent over most of Latin America. It may be very abundant in some areas (Rawlins 1979) and very troublesome to cattle, transmitting babesiosis. The tropical horse tick (Dermacentor nitens, fig. 4.6d) is distributed from Mexico to Argentina and on the Greater Antilles. It infests the ears of its hosts (horses mainly but also cattle, deer, and goats) where it undergoes its complete development.

Amblyomma is the largest genus, with fifty Neotropical species (Jones et al. 1972). Many exhibit beautiful colors and ornamentation. They are often large, flat, and almost circular in outline. Hosts are varied, usually mammals, but also reptiles, including turtles (Ernst and Ernst 1977), and often birds, in the larval and nymphal stages.

The cayenne tick (Amblyomma cajennense, fig. 4.6c), known as mostacilla or carrapato estrela, is a general nuisance in all parts of the Neotropics where it menaces both man and livestock (Hoffmann 1962). The larvae may swarm in thousands in grass and low herbage. Very little has been published on its natural biology (Drummond and Whetstone 1975), although methods for artificial culture have been worked out (Travassos and Vallejo-Freire 1944).

The tropical bont tick (A. variegatum) has been introduced from Africa to the Caribbean, where it is associated with strepto-thricosis, a bacterial skin disease of livestock (Garris 1987), and heartwater (caused by the rickettsia Cowdria ruminantium).

Ixodes pararicinus (once confused with the European castor bean tick, I. ricinus) is known widely as a parasite of cattle in the southern half of South America (Keirans et al. 1985).

Soft tick genera in Latin America are Otobius, Antricola, Argas, Nothoaspis, and Ornithodoros (Jones and Clifford 1972). Notable regional taxa are as follows. Argas are small and found on odd hosts. The twenty Latin American species are mostly associated with birds (owls, fowl, etc.) (Hoogstraal et al. 1979). A. persicus is the cosmopolitan fowl tick ("adobe tick," "tampan") and one of the most important poultry parasites. A. miniatus (fig. 4.6e), however, may more often be the offender in Latin America generally, A. moreli in Peru (Keirans et al. 1979). A. transversus attaches to the neck and throat skin of giant Galápagos tortoises (Hoogstraal et al. 1973). All are restricted to dry niches in desert to savanna life zones.

Ornithodorus talaje and (). rudis are common Neotropical species. They feed on wild rodents and most domestic animals and man and are vectors of the relapsing fever spirochete Borrelia in Guatemala, Panama, and Colombia. O. darwini and O. galapagensis have been described from the Galápagos iguanas (Kohls et al. 1969, Keirans et al. 1980). Antricola are found on bats or in their guano.

Members of both tick families are purveyors of numerous serious diseases of man and domestic animals (Arthur 1961, Hoogstraal 1981). Particularly serious to human health in Latin America are spotted fevers caused by rickettsial organisms (Hoogstraal 1967) and relapsing fevers brought on by Borellia. Rocky Mountain spotted fever is endemic in many parts of Latin America (Mexican spotted fever, fiebre manchada, Tobia fever, Sao Paulo fever) where it may be transmitted by almost any tick that lives on the mammalian hosts for the pathogens. Extensive use of one major vector, Amblyomma cajennense, has been applied to attempts to develop a vaccine for this virulent disease (Travassos and Vallejo-Freire 1944). Tick-borne viral diseases seem not to be a regional problem, but in general, these are not well studied in Latin America.

Among animals, domestic and wild, ticks transmit Texas cattle fever or red water fever (tristeza) caused by the protozoan Babesia bigernina, in various parts of the American tropics. The vector is usually Boophilus microplus. The disease destroys the red blood cells and has a very high mortality rate. Some natural control of these vectors by fire ants in Mexico has been discovered (Butler et al. 1979).

Ticks also cause local trauma and inflammation at the site of attachment and sometimes elicit a paralysis by the injection of some neurologically active substance in their saliva. Fortunately, tick paralysis (Murnaghan and O'Rourke 1978) is usually temporary, disappearing when the tick is removed, but recovery may be delayed and can cause death in young or sensitive people, especially when the bite focus is on the neck at the base of the skull.

The nonexistent tick "Ixodes maloni" was recorded from a Guianan tepui by Sir Arthur Conan Doyle in his fiction classic, The Lost World (Hoogstraal 1972).

References

Peterson, Evanston, 111. Butler, J. F., M. L. Camino, and T. M. Pérez. 1979. Boophilus microplus and the fire ant Solenopsis geminata. Rec. Adv. Acarol. 1: 469-472.

Drummond, R. O., and T. M. Whetstone. 1975. Oviposition of the cayenne tick, Amblyomma cajennense (F.), in the laboratory. Entomol. Soc. Amer. Ann. 68: 214-216.

Ernst, C. H., and F3. M. Ernst. 1977. Ectoparasites associated with Neotropical turtles of the genus Callopsis (Testudines, Emy-didae, Batagurinae). Biotropica 9: 139-142.

Garrís, G. 1. 1987. Amblyomma variegatum (Acari: Ixodidae): Population dynamics and hosts used during an eradication program in Puerto Rico. J. Med. Entomol. 24: 82-86.

Hoffmann, A. 1962. Monografía de los lxo-doidea de México. 1. Rev. Soc. Méx. Hist. Nat. 23: 191-307.

Hoogstraal, H. 1967. Ticks in relation to human diseases caused by Rickettsia species. Ann. Rev. Entomol. 12: 377-420.

Hoogstraal, H. 1972. Ixodes maloni Doyle, 1912 (nomen nudum) (Ixodoidea: Ixodidae) parasitizing humans in Brazil. Entomol. Soc. Amer. Bull. 18: 141.

Hoogstraal, H. 1981. Changing patterns of tickborne diseases in modern society. Ann. Rev. Entomol. 26: 75-99.

Hoogstraal, H., C. M. Clifford, and J. E. Keirans. 1973. Argas (Microargas) transnersus (Ixodoidea: Argasidae) of Galápagos giant tortoises: Description of the female and nymph. Entomol. Soc. Amer. Ann. 66: 727-732.

Hoogstraal, H., C. M. Clifford, J. E. Keirans, and H. Y. Wassef. 1979. Recent developments in biomedical knowledge of Argas ticks (Ixodoidea: Argasidae). Ree. Adv. Acarol. 2: 269-278.

Jones, E. K., and C. M. Clifford. 1972. The systematics of the subfamily Ornithodorinae (Acariña: Argasidae). V.A. revised key to larval Argasidae of the Western Hemisphere and description of seven new species of Ornithodoros. Entomol. Soc. Amer. Ann. 65: 730-740.

Jones, E. K., C. M. Clifford, J. E. Keirans, and G. M. Kohls. 1972. The ticks of Venezuela (Acariña: Ixodoidea) with a key to the species of Amblyomma in the Western Hemisphere. Brigham Young Univ. Biol. Ser. 17(4): 1-40.

Keirans, J. E., C. M. Clifford, A. A. Gu-glielmone, and A. J. Mangold. 1985. Ixodes (Ixodes) pararicinus, n. sp. (Acari: Ixodoidea: Ixodidae), a South American cattle tick long confused with Ixodes ricinus. J. Med. Entomol. 22: 401-407.

Keirans, J. E., C. M. Clifford, and H. Hoogstraal. 1980. Identity of the nyinphs and adults of the Galápagos iguanid lizard parasites, Ornithodoros (Alectorobius) darwini and O. (A.) galapagensis (Ixodoidea: Argasidae). J. Med. Entomol. 17: 427-438.

Keirans, J. E., H. Hoogstraal, and C. M. Clifford. 1979. Observations on the subgenus Argas (Ixodoidea: Argasidae: Argas). 16. Argas (A.) moreli, new species, and keys to Neotropical species of the subgenus. J. Med. Entomol. 15: 246-252. Kohls, G. M., C. M. Clifford, and H. Hoogstraal. 1969. Two new species of Ornithodoros from the Galápagos Islands (Acariña: Argasidae). J. Med. Entomol. 6: 75-78.

Murnaghan, M. F., and F.J. O'Rourke. 1978. Tick paralysis, In S. Bettini, ed.. Arthropod venoms. Springer, Berlin. Pp. 419-464. Obenchain, F. D., and R. Galun, eds. 1982. The physiology of ticks. Pergamon, New York.

Oliver, Jr, J. H. 1989. Biology and systematics of ticks (Acari: Ixodida). Ann. Rev. Ecol. Syst. 20: 397-430. Rawlins, S. C. 1979. Seasonal variation in the population density of larvae of Boophilus microplus (Canestrini) (Acari: Ixodoidea) in Jamaican pastures. Bull. Entomol. Res. 69: 87-91.

Travassos, J., and A. Vallejo-Freire. 1944. Criagäo artificial de Amblyomma cajennense para o preparo de vacina contra a febre maculosa. Inst. Butantan Mem. 18: 1-91. Yunker, C. E., J. E. Keirans, C. M. Clifford, and E. R. Easton. 1986. Dermacentor ticks (Acari: Ixodoidea: Ixodidae) of the New World: A scanning electron microscope atlas. Entomol. Soc. Wash. Proc. 88: 609-627.

whip scorpions

Uropygi (= Pedipalpida, in part). Spanish: Vinagrosos, vinegrones (General), vinagrillos (Mexico). Vinegarroons.

A whiplike flagellum extending from the tip of the abdomen gives this group its common name. Other distinctive characteristics include a longer than wide prosoma, spiderlike chelicerae, and massive pedi-palps equipped with short but strong spines (Weygoldt 1972). The first legs are feelerlike and slightly longer than the others, which are relatively short and held close to the body. A pair of defensive glands that open near the anus secrete formic and acetic acid, among other com

Figure 4.7 WHIP SCORPIONS AND PSEUDOSCORPION. (a) Vinegarroon (Mastigoproctus giganteus, Elyphonidae). (b) Tailless whip scorpion (Heterophrynus longicornus, Phrynidae). (c) Pseudoscorpion (Chelifer cancroides, Cheliferidae).

pounds (e.g., caprylic acid, a wetting agent). These compounds may be forcibly expelled from the anus as a means of chemical protection (Eisner et al. 1961).

These animals are nocturnal predators that live on the ground, for example, under litter and stones and in stumps (Kaestner 1968: 117-119). Mastigoproctus giganteus (fig. 4.7a) actively excavates tunnels in the ground where it remains during the daytime. Those most often encountered are the vinagrillos (so-called because of their vinegar odor when defending themselves with their chemical sprays) of the genus Mastigoproctus. Specimens visit the vicinity of artificial lights at night, particularly in desert areas, to feast on insects attracted to the illumination. They are large (BL to 7 cm), dark brown to black, and heavily sclerotized. In spite of their fearsome scorpionlike appearance, they do not bite or sting.

Whip scorpions prefer humid conditions and are mostly found in tropical climes. Those that inhabit arid regions appear only after rains.

There are representatives of two families in Latin America (Rowland and Cooke 1973). Most are of the family Elyphonidae, the largest genus being Mastigoproctus with twelve species. The one species of Thelyphro-nellus is restricted to Guyana and northeast ern Brazil, as is Arnauromastigon, the single genus and species of the other family, Hypoctonidae.

References

Eisner, T., J. Meinwald, A. Monro, and R. Ghent. 1961. Defense mechanisms of arthropods. I. The composition and function of the spray of the whip scorpion, Mastigoproctus giganteus (Lucas) (Arachnida, Pedipalpida). J. Ins. Physiol. 6: 272-298. Kaf.stner, A. 1968. Invertebrate zoology, arthropod relatives, Chelicerata, Myriapoda. Vol. 2. Wiley Interscience, New York. Rowland, J. M., and J. A. L. Cooke. 1973. Systematics of the arachnid order Uropygida ( = Thelyphonida). J. Arachnol. 1: 55-71. Wf.ygoldt, P. 1972. Geisseiskorpione und Geisseispinnen (Uropygi und Amblypygi). Zeit. Kölner Zoo. 15(3): 95-107.

0 0

Post a comment