Assassin Bugs

Reduviidae.

These are mostly medium to large bugs of varied form but always with a narrowly attached, elongate head that bears a flexible, segmented beak and fairly long antennae. At rest, the beak fits neatly into a pronounced furrow on the underside of the head which has microscopically visible cross striations on its inner surface. In many species, the forelegs are modified for grasping small insect prey. The prothorax is trapezoidal and often bears sharp spines at its outer corners. The abdomen is usually broad and expands markedly beyond the margins of the folded wings. Typical examples are found in the widespread genera Apiomerus (fig. 8.3a) and Arilus. The widespread cogwheel bug (chinche crestada, Arilus carinatus) is large (BL 20 mm) and easily recognized by a prominent, vertical, semicircular crest on the back of the thorax which is margined with coarse teeth (fig. 8.3b).

Members of the subfamily Emesinae, called thread-legged bugs, are sticklike (fig. 8.4c) and often mistaken for phasmids (Wygodzinsky 1966). Some of these are known to steal prey caught in spiders' webs.

Many assassin bugs are brightly colored, with red or yellow legs and spots that appear on the back of the abdomen when the wings are raised. The brightly colored, spiny nymphs are a common sight on low vegetation in forests. Their brilliant markings (pi. 3d) obviously warn enemies of their venomous and painful bite (apose-matic). Many such species participate in Mtillerian mimicry complexes with other insects. Remarkable examples are certain Spijiiger that closely resemble tarantula

Figure 8.3 ASSASSIN BUGS (REDUVIIDAE). (a) Assassin bug (Apiomerus lanipes). (b) Cogwheel bug (Arilus carinatus). (c) Tarantula hawk model for tarantula hawk-mimicking assassin bug (pepsis sp., Pompilidae). (d) Tarantula hawk-mimicking assassin bug (Spiniger sp.). (e) Trash-gathering assassin bug (Salyavata variegata).

Figure 8.3 ASSASSIN BUGS (REDUVIIDAE). (a) Assassin bug (Apiomerus lanipes). (b) Cogwheel bug (Arilus carinatus). (c) Tarantula hawk model for tarantula hawk-mimicking assassin bug (pepsis sp., Pompilidae). (d) Tarantula hawk-mimicking assassin bug (Spiniger sp.). (e) Trash-gathering assassin bug (Salyavata variegata).

hawks (spider wasps of the genus Pepsis) (fig. 8.3c, d) as well as Hiranetix and Graptocleptes, which are colored and behave like band-winged, ichneumonid wasps. Notocyrtus vesiculosas mimics the stingless bee, Trígona fulviventris, both species having a black head, thorax, and legs, and orange-yellow abdomen (Jackson 1973). Apiomerus pictipes (Johnson 1983) has been observed in Mexico feeding on Trígona bees, which it resembles and which it seems to be attracted by some agent, possibly a chemical lure (Weaver et al. 1975).

A species with another deceptive hunting strategy is Salyavata variegata (fig. 8.3e), whose nymph lives in nasute termite nests in Costa Rica. For camouflage, it scratches off bits of nest and plasters them to hairlike projections on its back. It also "fishes" for termites, using the empty carcasses of previous prey as a lure. Workers are attracted to their own dead as a source of protein; when a termite takes the "bait," the bug drops it and grabs the fresh prey (McMahan, 1982, 1983).

Assassin bugs, as their name suggests, are fiercely predaceous. All feed on blood from other insects. (Those of the subfamily Triatominae suck vertebrate blood; see Kissing Bugs, below.) They attack mercilessly, using their raptorial forelegs to grasp and hold their victims while they stab with their mouth stylets. Chemicals contained in the saliva immobilize their captives and can cause considerable pain when used as a defensive "sting" against vertebrates and humans. Because of their insectivorous habits, assassin bugs are important controllers of crop pest and natural insect populations.

Just over a thousand species of Redu-viidae are recorded from Latin America (Wygodzinsky 1949).

References

Jackson, J. F. 1973. Mimicry of Trígona bees by a reduviid (Hemiptera) from British Honduras. Fla. Entomol. 56: 200-202. Johnson, L. K. 1983. Apiomerus pictipes (redu-vio, chinche asesina, assassin bug). In D. H. Janzen, ed., Costa Rican natural history. Univ. Chicago Press, Chicago. Pp. 684-687. McMahan, E. A. 1982. Bait-and-capture strategy of a termite-eating assassin bug. Ins. Soc. 29: 346-351. McMahan, E. A. 1983. Bugs angle for termites.

Nat. Hist. 92(5): 40-47. Weaver, E. C., E. T. Clarke, and N. Weaver. 1975. Attractiveness of an assassin bug to stingless bees. Kans. Entomol. Soc. J. 48: 17-18. Wygodzinsky, P. 1949. Elenco sistemático de los Reduviiformes Americanos. Univ. Nac. Tucu-mán Publ. 473, Monogr. 1: 1-102. Wygodzinsky, P. 1966. A monograph of the Emesinae (Reduviidae, Hemiptera). Amer. Mus. Nat. Hist. Bull. 133: 1-614.

Kissing Bugs

Reduviidae, Triatominae, Panstrongylus, Triatoma, and relatives. Spanish: Chirimachas (Peru), vinchucas (Argentina, Chile), pitos (Venezuela), chinches voladoras (Mexico), chinches

yuru pucu (Paraguay). Portuguese: Bichos de parede, chupangas, pinchadores, barbeiros, fincoes (Brazil). Conenose bugs.

These Reduviidae are of major medical importance in the New World tropics because of the role of several species as vectors of Chagas' disease (Zeledon and Rabinovich 1981). This is a very debilitating and frequently fatal syndrome caused by the protozoan Trypanosoma (Schizotry-panum) cruzi. The pathogens are introduced by the bug when it feeds, not directly through the bite but in liquid fecal material that it habitually releases following engorgement. The microorganisms in these droppings enter through the perforation made by the bite or through the mucous membranes. The site of inoculation may be anywhere on the skin, but infection commonly occurs at the outer corner of the eye. The parasites multiply rapidly and localize eventually in vital internal organs; after years of chronic disease, the patient often succumbs. Chagas' disease is restricted to the New World ("American trypanosomiasis"), and although the pathogen occurs in its bug and intermediate wild mammal hosts over a much wider area, it is prevalent principally in dry areas of marginal agriculture throughout southern Mexico, around the periphery of the Amazon Basin (but apparently not within, even though vectors are present; Barbosa de Almeida 1971), and across the middle of South America. It is estimated that 13 to 14 million people in South America suffer from the disease at this time.

In 1909, Carlos Chagas first discovered the flagellate in the triatomine bug, Panstrongylus megistus (fig. 8.4a). Since that time, several other species in this subfamily of bloodsucking bugs have been incriminated as transmitters. The most effective vector seems to be the widely distributed, often domestic, Triatoma infestans (Rabinovich 1972). Other important general vectors are T. dimidiata in Central America, Ecuador, and Peru and Rhodnius pallescens in Panama. Several species of Panstrongylus (Lent and Jurberg 1975) and Triatoma and Rhodnius prolixus (fig. 8.4b) are localized vectors in different parts of Latin America (Lent and Wygodzinsky 1979: 135f.). Many more triatomines have been found naturally infected with the parasite.

Kissing bugs are mostly medium to fairly large reduviids (BL 10—45 mm). The head is cylindrical, about three times as long as wide, and has a constricted, cone-shaped anterior portion from which the three-segmented beak arises. A membranous connection between the second and third rostral segments, permitting flexure of the third segment during bloodsucking, is a unique condition among bugs. The abdomen is concave dorsally and widely expanded laterally. In many species, these expansions are conspicu

Figure 8.4 HETEROPTERANS. (a) Kissing bug (Panstrongylus megistus, Reduviidae). (b) Kissing bug (Rhodnius prolixus, Reduviidae). (c) Thread-legged bug (Empicoris rubromaculatus, Reduviidae). (d) Bat bug (Hesperoctenes sp., Polyctenidae). (e) Bedbug (Cimex lectularius, Cimicidae).

ously banded alternately with light and dark colors. The general body color is black or brown, with well-defined harlequin or variegated patterns of light yellow, orange, or red.

The main biological feature of kissing bugs is their obligate, vertebrate blood-feeding habits. All species need this blood to complete their life cycle. Their primary habitat is the nest of their hosts and nearby confined refuges (under bark, rock crevices, crowns of palms, etc.) where they hide during the day, emerging at night to feed on vertebrates visiting these niches. Many species are domestic, occurring in poultry pens and stock corrals and habitations, especially mud or adobe huts.

Adults rarely fly but occasionally are attracted to lights at night. Most have a long life cycle, 300 days on the average from egg to adult; some two years. Others complete development in less than a year and may have two to three generations per annum. There are five nymphal stages. When disturbed, many species release a pungent odor from metathoracic glands (Schofield and Upton 1978). The active chemical is butyric acid, which is repugnant to humans and other animals, including ants. Other aspects of the behavior of Triatominae are reviewed by Schofield (1979).

Because of their voracious appetites for human blood, kissing bugs were well known to the indigenous Americans and have attracted attention historically since early colonial days. Fray Reginaldo de Lizarraga was the first to describe the bugs in 1590 (Abalos and Wygodzinsky 1951).

The subfamily contains five tribes with 13 genera and 111 species in the Western Hemisphere, whose vector importance, classification, and structure have been thoroughly reviewed (Lent and Wygodzinsky 1979, Usinger et al. 1966). Bibliographies of Chagas' disease and lists of species of the kissing bugs of Latin America are also available (Ryckman 1984, 1986; Ryckman and Blankenship 1984; Ryckman and Zackrison 1987).

Rhodnius prolixus colonies are now widely used as experimental animals in many laboratories as a result of the pioneering work of insect physiologist V. B. Wigglesworth.

References

Abalos, J. W., and P. Wygodzinsky. 1951. La vinchuca: Folklore y antecedentes históricos. Cien. Invest. 7: 472-475. Barbosa de Almeida, F. 1971. Triatomíneos da

Amazonia. Acta Amazónica 1: 89-93. Lent, H., and J. Jurberg. 1975. O género Panstrongylus Berg, 1879, com um estudo sobre a genitalia externa das especies (Hemiptera, Reduviidae, Triatominae). Rev. Brasil. Biol. 35: 379-438. Lent, H., and P. Wygodzinsky. 1979. Revision of the Triatominae (Hemiptera, Reduviidae), and their significance as vectors of Chagas' disease. Amer. Mus. Nat. Hist. Bull. 163: 123-520.

Rabinovich, J. E. 1972. Vital statistics of Triatominae (Hemiptera: Reduviidae) under laboratory conditions. I. Triatoma infestans Klug. J. Med. Entomol. 9:351-370. Ryckman, R. E. 1984. The Triatominae of North and Central America and the West Indies: A checklist with synonymy (Hemiptera: Reduviidae, Triatominae). Soc. Vector Ecol. Bull. 9: 71-83. Ryckman, R. E. 1986. The Triatominae of South America: A checklist with synonymy (Hemiptera: Reduviidae: Triatominae). Soc. Vector Ecol. Bull. 11: 199-208. Ryckman, R. E., and C. M. Blankenship. 1984. The Triatominae and Triatominae-borne trypanosomes of North and Central America and the West Indies: A bibliography with index. Soc. Vector Ecol. Bull. 9: 112-430. Ryckman, R. E., and J. L. Zackrison. 1987. A bibliography to Chagas' disease, the Triatominae and Triatominae-borne trypanosomes of South America (Hemiptera: Reduviidae: Triatominae). Soc. Vector Ecol. Bull. 12: 1-464.

Schofield, C. J. 1979. The behavior of Triatominae (Hemiptera: Reduviidae): A Review. Bull. Entomol. Res. 69: 363-379. Schofield, C. J., and C. P. Upton. 1978. Brindley's scent-glands and the metasternal scent-glands of Panstrongylus megislus (Hemiptera, Reduviidae, Triatominae). Rev. Brasil. Biol. 38: 665-678.

Usinger, R. L., P. Wygodzinsky, and R. E. Rvckman. 1966. The biosystematics of Triato-minae. Ann. Rev. Entomol. 11: 309-330. Zeled6n, R., and J. E. Rabinovich. 1981. Chagas' disease: An ecological appraisal with special emphasis on its insect vectors. Ann. Rev. Entomol. 26: 101-133.

Parasitic Bugs

Bugs in two heteropteran families have lost their wings and become totally adapted for a parasitic existence on the bodies, or in the nests, of birds and mammals. Among these, the Polyctenidae, or bat bugs, are the more extremely modified structurally and biologically, for life on bats. They are small (BL 3 to 5 mm), lack eyes, are flattened, and have comblike rows of flattened spines on the body (fig. 8.4d). The females are viviparous (Ryckman and Casdin 1977). A single genus, Hesperoctenes, is present in the New World (Ueshima 1972).

The cimicids, or bedbugs, are much better known because of the two species that associate closely with mankind. They are not well adapted to cling to fur or leathers but are temporary visitors to the body of the host, normally bats and various birds. Most common and best known are the introduced domestic bedbugs (Cimex lec-tularius and C. hemipterus) on bats, chickens, and humans throughout America (see below). Also of economic importance are the parrot bedbug (Psitticimex), on parrots in northern Argentina, the Mexican chicken bug (Haematosiphon inodorus), on chickens in Mexico (Lee 1955), and the Brazilian chicken bug (Ornithocoris toledoi), which, prior to its control with organic insecticides, was a pest on chickens in southeastern South America.

Twelve genera of cimicids are found in Latin America. The absence of native species in Central America, where only the domestic pests are represented, is a curious distribution pattern among New World bedbugs (Ryckman et al. 1981, Usinger et al. 1966).

Cimicids are larger than polyctenids (BL 4-5 mm), more or less oval, and slightly flattened. The abdomen is soft and capable of enormous enlargement with blood at the time of engorgement. They are flightless, but padlike, vestigial fore wings persist in most species.

A unique development in this family is the presence of a secondary copulatory receptacle (spermalege) in the female, situated on one side, at the base of the abdomen. The male genitalia are asymmetrical and possess a formidable, swordlike penis. Males perforate the integument with this intromittent organ in one or more places, usually through an external fold in an intersegmental membrane over the receptacle. The sperm is then delivered to an underlying pocket that communicates with the genital ducts. Copulation with the female's normal terminal genitalia never occurs.

References

Lef., R. D. 1955. The biology of the Mexican chicken bug, Haematosiphon inodorus (Duges) (Hemiptera: Cimicidae). Pan-Pacific Entomol. 31: 47-61. Ryckman, R. E., D. G. Bentley, and E. F. Arch-bold. 1981. The Cimicidae of the Americas and oceanic islands: A checklist and bibliography. Soc. Vector Ecol. Bull. 6: 93-142. Ryckman, R. E., and M. A. Casdin. 1977. The Polyctenidae of the world, a checklist with bibliography. Calif. Vector Views 24: 25-31. Ueshima, N. 1972. New World Polyctenidae (Hemiptera), with special reference to Venezuelan species. Brigham Young Univ. Sci. Bull. (Biol. Ser.) 17: 13-21. Usinger, R. L., J. Carayon, N. T. Davis, N. Ueshima, and H. E. McKean. 1966. Monograph of Cimicidae. Vol. 7. Entomol. Soc. Amer. (Thomas Say Foundation), College Park, Md.

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