Presentations
Table of species
Triatominae
Assassin Bugs
Links
Presentions
Part 1, Part 2 (powerpoint) of Francisco Panzera (Homepage), second meeting, Rio March 2004.Molecular phylogeopraphy of Chagas disease vectors in the Amazon: vector control implications (powerpoint) of Fernando Monteiro, ICOBICOBI, Angra, October 2004.
Table of family
There are 130 species in the Triatominae family, shown in Table 1. source.
The follow chapter is from Dr. Rose
TriatominaeThe Triatominae are a subfamily of the Reduviidae, or assasin bugs. There are 118 known species (with sizes from 5 mm to 45 mm) and 14 genera. All are obligate bloodsuckers, regardless of age and sex. More than half of them were proven to have the ability to carry Trypanosoma cruzi, the flagellate that causes Chagas disease (Schofield & Dolling 1993 - see the literature list for complete references). Due to their biology and close association with humans, the most important vectors of Chagas disease are Triatoma infestans, Triatoma brasiliensis, Triatoma dimidiata, Triatoma sordita, Rhodnius prolixus, and Panstrongylus megistus (Schofield 1994).
Host-finding of Triatomine bugs
Triatomine bugs usually leave their refuge during the night to search for their host (Lent & Wygodzinsky 1979; Schofield 1979; Núñez 1987; Schofield & Dolling 1993; Schofield 1994). In different experimental setups Triatomine bugs were attracted using potential hosts such as a hamster (Núñez 1982), mice (Taneja & Guerin 1995, Rose & Boeckh 1996b), and humans (Rose & Boeckh 1996a/b). However, the role of individual stimuli such as heat and host odors, including carbon dioxide, is not entirely understood. Rose & Boeckh (1996a) demonstrated that breath is a major stimulus used in the orientation toward the host in Triatoma infestans. The work published so far has been conducted only in the laboratory.
"The olfactory and thermal senses reside chiefly in the antennae, which serve also to perceive air currents and contact" (Wiggelsworth & Gillet 1934). Mayer (1968) successfully recorded electrophysiological responses of singele cells in olfactory receptors on the antennae of Triatoma infestans towards breath, Bernard (1974) towards other host odors.
Warmth
Early findings by Hase (1932) with different species from Venezuela
(Panstrongylus geniculatus, Rhodnius pictipes, and Eratyrus
cuspidatus) already indicated that warmth is a major reason for the extension
of the proboscis. Wiggelsworth & Gillet (1934) confirmed the dominant
role of warmth for short distance orientation for Rhodnius prolixus.
A warm test tube alone elicited probing. Nicolle & Mathis (1941) also
reported probing responses towards warm bodies by Triatoma infestans
and Rhodnius prolixus. Over a short distance, a warm current of air
was shown to be attractive for already active Triatoma infestans and
to elicit probing (Wiesinger, 1956). However, it did not activate resting
animals. Núñez (1982) reported that nymphs of Rhodnius
prolixus were not activated by warmth. In an olfactometer, they were
only slightly attracted, compared to other host odors and carbon dioxide.
This was interpreted as an indication that warmth plays only a smaller role
in the orientation towards the host over longer distances. Lazzari &
Núñez (1989) showed that Triatoma infestans nymphs are
able to perceive radiant head and to distinguish between different temperatures
of radiant heat sources.
During his studies of olfactory sensilla of Triatoma infestans, Mayer (1968) did not find any response when he increased or decreased the temperature near the receptor. Lazzari & Wicklein (1994) recorded electrophsysiological activity of the so-called cave-like sense organ in the antennae of Triatoma infestans in response to thermal stimuli.
Carbon dioxide
The role of carbon dioxide was first investigated by Wiesinger (1956).
She concluded that a warm (36 - 40 °C) mixture of carbon dioxide and
air is more attractive for T. infestans than warm air alone, both
in the activation and orientation responses towards the stimulus source.
Núñez (1982) attracted nymphs of Rhodnius prolixus in
an olfactometer with carbon dioxide. Rose & Boeckh (1996b) report similar
findings for second instar Triatoma infestans. Both Triatoma
infestans and Rhodnius prolixus also showed oriented responses
towards carbon dioxide on a servosphere (Taneja & Guerin 1995). Guerenstein
et al. (1995) were able to attract Triatoma infestans using an aerobic
cultures of yeast on saccrose. The attraction of these cultures was reduced
when the cabon dioxide realesed was partially eliminated using potassium
hydroxide. A warm carbon dioxide source was shown to be attractive for nymphs
of Triatoma infestans in an enclsure resembling the natural environment
of the bugs (Rose & Boeckh 1996a).
Mayer (1968) reports responses of olfactory sensilla towards carbon dioxide and carbon monoxide. However, these responses were not as strong as those towards breath.
Other host odors
Other host odors also seem to play a role in host orientation.
Wiggelsworth & Gillet (1934) state that during their experiments, some
bugs also oriented towards the test tube at room temperature when it was
covered with a fresh mouse skin. However, they failed to probe it. No evidence
was obtained of either attraction or repulsion by moisture. Núñez
(1982) attracted nymphs of Rhodnius prolixus in an olfactometer using
his fore arm. Hamster odors were still attractive when they were bubbled
through a mixture of potassium hydroxide and water, thus removing both carbon
dioxide and lactic acid. Indications that mice give off attractive odors
are given by Torres-Estrada & Martínez-Ibarra (1993): They report
that starving nymphs of Triatoma gerstaeckeri chose mice nests as
a hiding-place, whereas fed animals preferred stone walls. Taneja & Guerin
(1995) showed oriented responses of nymphs of Rhodnius prolixus and
Triatoma infestans on a servosphere towards rabbit urine odors. Rose
& Boeckh (1996b) attracted second instar Triatoma infestans using
worn socks as a stimulus source. In 1997, Taneja & Guerin reported that
ammonia at doses of 3 to 17 ppb attracted Triatoma infestans nymphs
on a servosphere. They had detected ammonia both in stale rabbit urine odors
as well as in wetted papers with triatomine feces.
The olfactory sensilla studied by Mayer (1968) also showed responses to some chemicals associated with human breath odors (methanol, methane, furan, pyridine). However, these responses were not as strong as those towards breath. Bernard (1974) also reports electrophsiological responses of sensilla on the antenna of Triatoma infestans towards complex host odors (a finger, sweat), as well as individual chemicals such as lactic acid or butyric acid. Taneja & Guerin (1997) recorded electroantennograms as well as electrophysiological responses of single receptor cells in Triatoma infestans nymphs towards ammonia.
Triatoma infestans (Klug 1834)
Size: males 21-26 mm, females 26-29 mm.
Distribution: From eastern and southern Brazil and the
southern half of Bolivia down to the Argentinian province of Chubut. In all
of Paraguay and the largest part of Uruguay. East of the Andes in northern
Chile and southern Peru. In Bolivia, T. infestans was recorded to
reach altitudes of 4100 m.
The species is almost exclusively domestic and peridomestic. Sylvatic colonies
are only reported from Bolivia, where they were associated with wild guinea
pigs. But usually, the animals are found in human habitations, chicken houses,
stables, enclosures or corrals.
Further informations are from William F. Lyon
Assassin Bugs
HYG-2082-98
 | |
|---|---|
| Common Name | Scientific Name |
| Bloodsucking Conenose | Triatoma sanguisuga (LeConte) |
| Masked Hunter | Reduvius personatus (Linnaeus) |
| Black Corsair | Melanolestes picipes (Herrich-Schaeffer) |
| Wheel Bug | Arilus cristatus (Linnaeus) |
| Spined Assassin Bug | Sinea diadema (Fabricius) |
Assassin bugs, sometimes known as conenoses or "kissing bugs," are occasionally found in the home (bathtubs, sinks, drains, etc.) and, if handled carelessly, can inflict a very painful bite, causing a severe reaction in some persons. Some are attracted to lights and require blood meals to complete their development. Many are bloodsucking parasites of mammals, including humans. Others are predators, feeding on bed bugs, flies, caterpillars and other insects. Most are found in late June to early August. These bugs have a long narrow head, short beak (three-segmented), long slender antennae (four-segmented) and an abdomen often widened at the middle exposing the margins of the segments beyond the wings. Occasionally, they are confused with the leaffooted bug which is distinguished by its flattened (leaf-like) hind legs.
Identification, Biology and Behavior
Bloodsucking Conenose
Adults are 3/4 to 13/16 inch long, brownish-black, broad, stout-bodied with six reddish orange spots on each side of the abdomen, above and below. Eyes are large with an elongate protruding head. The beak is not curved (slender and tapered) and almost bare. It is kept folded back between the front legs when not used. Adults are winged and able to fly. They are found in nests of rats and will feed on any animal including humans. Oval, pearly-white eggs are laid singly from May to September. Each batch is laid after a blood meal. Nymphs have eight instars requiring three years for the life cycle.
The conenose is a vector of Chagas disease prevalent in Mexico, Central America, and South America, where these bugs may colonize human habitations. This sometimes fatal disease, caused by a flagellate protozoan, has symptoms of swelling of the eyelids and face, loss of nervous control, high fever, anemia and destruction of the cardiac and skeletal muscles. This disease is not common in the United States.
The bloodsucking bugs are active at night usually feeding on sleeping victims. These bugs are usually found outdoors in hollow trees, in raccoon and opossum dens, or near wood rat nests. Indoors, they are found in bedding, floor and wall cracks, under furniture, etc. They are poor fliers and sometimes attracted to lights. Bites are sometimes painless, but may cause a severe reaction. They are more often a problem to people living in wooded areas.
Masked Hunter
Adults are 3/4 to 7/8 inch long, chocolate brown, beak curved (not slender and tapered), with slender antennae and walking-type legs. They are called "kissing bugs" and are attracted to lights. They are very active and enter houses in search of bed bugs, flies, and other insects. Eggs are laid singly in the dust in cracks and corners. Nymphs have the body, legs, and antennae covered with a sticky substance to which dust and lint adhere especially on the head (thus, the name, masked) and are only visible when moving. Nymphs hibernate in the 4th to 5th instar and reach maturity the following spring. Bites are very painful on humans.Black Corsair
Adults are black and 9/16 to 11/16 inch long. They resemble the masked hunter except have short wings. Adults overwinter under stones and are collected in early spring. Bites are painful to humans.Wheel Bug
Adults are 1-1/4 inch long and have a slender, long antennae (reddish-brown). The body is grayish-black with an upright one-half "cogwheel-like" crest on the thorax bearing 8 to 12 protruding teeth-like structures. The membrane of the front wing is coppery colored. Wheel bugs are rather uncommon, but attract attention when found due to their bizarre appearance. They are voracious predators, attacking large caterpillars, such as tomato hornworms, and suck them dry. They will not bite humans readily, but when they do, the bite is very painful.Spined Assassin Bug
Adults are 1/2 to 9/16 inch long, brown colored, narrow, angular, and rough-bodied. The head, thorax (middle part) and front leg (upper portion) are covered with spines and the female's abdomen is wavy. Cylindrical white eggs are laid in small groups covered with a reddish secretion. These bugs are very beneficial to agriculture, feeding on many injurious insects, attacking all stages of the Mexican bean beetle.First Aid
Bites may be hardly felt by the bloodsucking conenose in contrast to painful bites by the masked hunter, black corsair, and wheel bug. Sensitive individuals may experience burning pain, intense itching and much swelling with red blotches and welts over the body. If bitten, remain calm and safely collect the bug for positive identification. Do not handle bugs without gloves. Contact your local poison information center to seek medical help. Relief from bites may be obtained by using lotions containing menthol, phenol or camphor.Control Measures
Prevention
All potential breeding areas such as rodent and bird nests and trash piles in or near houses should be eliminated. Since these bugs fly at night and are attracted to light, adequate screening must be used around windows and doors. Use non-attractive insect yellow lights, if possible. Be sure to caulk and seal any openings into the house. Should a bug alight on one's face or hand, it should be brushed off gently since it is likely to bite if pinched or crushed. Usually only a few individual bugs are found in the home at one time except for the bloodsucking conenose, which may be in groups of 10 to 15 at a time or scattered singly. Do not handle bugs. Use a broom and dustpan or vacuum cleaner to collect and discard individuals.Insecticides
A household aerosol spray of pyrethrins can give good knockdown and kill against individuals. These bugs can be controlled with a spot treatment of a residual household crawling insect spray such as diazinon or propoxur (Baygon). Pyrethroid insecticides such as permethrin is the most effective at high concentrations. Before using any insecticide, always read the label, follow directions and safety precautions.All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868
More links to the biology of the tratorine:
The kiss of deathWHO
Description of Triatoma infestans family