Triatoma dimidiata

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Geographic Range

Triatoma dimidiata is found throughout Central America and in the northern parts of South America, including Mexico, Panama, Costa Rica, Colombia, Peru, Ecuador, and Guatemala. (Dorn, et al., 2009; Dorn, et al., 2007; Zeledon, et al., 1970a)

Habitat

Triatoma dimidiata is found both in the wild and in human dwellings throughout its geographic range. Sylvatic populations are normally found in areas with large amounts of potential hosts, such as rain forests. These populations can generally be found in holes of trees and rock piles. Domestic populations are found in domiciles in which a large amount of people reside. These populations tend to be more numerous in homes with larger groups of people or other animals, such as pets, as there are more potential hosts. (Dorn, et al., 2007; Monroy, et al., 2003; Payet, et al., 2009)

  • Range elevation
    150 to 1400 m
    492.13 to 4593.18 ft
  • Average elevation
    250 m
    820.21 ft

Physical Description

Triatoma dimidiata is a long, wide insect with a long snout featuring mouthparts modified for piercing and sucking blood meals from a host. They have an antennae with four segments and a large compound eye on each side of their head. They have six legs, and a pair of wings protruding from behind the first abdominal segment. They range in color from yellow to black, and have patterns of color on their backs that tend to be black, orange, brown, and yellow. Their backs are also covered in very short hairs. Their legs and pronotum are completely black. They are oblong in shape with relatively flattened, thin bodies when they are without a blood meal. (Lehmann, et al., 2005)

Females and males greatly differ in mass. Females range in mass from an average of about 0.28 g before a blood meal to an average of about 0.56 after a blood meal. Males range in mass from an average of about 0.23 before a blood meal to an average of about 0.45 following a blood meal. (Zeledon, et al., 1970a)

  • Sexual Dimorphism
  • female larger
  • Range mass
    0.229 to 0.565 g
    0.01 to 0.02 oz
  • Range length
    24 to 35 mm
    0.94 to 1.38 in
  • Average length
    30.5 mm
    1.20 in

Development

Eggs of Triatoma dimidiata are small ellipsoids that grow to around 2 mm. Upon hatching, the insects begin development into the first of five instars. Each instar displays a darker reddish-brown color. The instars can be distinguished from each other by size, as each instar nymph is significantly larger than the last. Instar nymphs can also be discerned by the number of bristles located on the dorsal side of their bodies. The first instar nymphs have just a few erect bristles, which the second to the fifth instar nymphs have progressively more, curved bristles. On the fourth instar nymph, the development of wings is apparent, and is increasingly more visible on the fifth instar nymph. After this fifth instar nymph completes its final molt, it develops into a full size adult with functional wings. (Mello, et al., 2009)

Each instar nymph is larger than the last, and takes more time to reach the next stage than it took to reach the current stage. Complete development of an egg to an adult Triatoma dimidiata takes an average of about 267 days for a female and an average of about 275 days for a male. Instar nymphs cannot complete development into the next stage without an adequate blood meal. (Zeledon, et al., 1970a)

Reproduction

Currently, mating systems for Triatoma dimidiata are not well understood. It is known that members of this species are polygynandrous. (Rebollar-Tellez, et al., 2009)

Triatoma dimidiata have the potential to produce thousands of eggs in their lifetime. As the species is more abundant and active in the hot and humid summer months, from March to July, more eggs are fertilized in this period. Females lay from about 9 to 31 eggs per day. Only about 90% of these eggs are fertile, however. Like many other insects, female T. dimidiata have a spermatheca in which they store sperm deposited by male T. dimidiata and fertilize eggs when they are ready. Female T. dimidiata normally have 2 to 3 eggs in their spermatheca at a time. Eggs are laid in refuge, where fertilized eggs will hatch into 0.0015 g nymphs. Nymphs will go through five instars spanning 11 months, after which they will be fully-developed adults. (Rebollar-Tellez, et al., 2009; Zeledon, et al., 1970a; Zeledon, et al., 1970b)

  • Breeding interval
    Triatoma dimidiata females lay 9 to 31 eggs every day, but most are unfertilized.
  • Breeding season
    Although Triatoma dimidiata is capable of breeding year-round, most breeding occurs from March to July.
  • Range number of offspring
    446 to 2054
  • Range gestation period
    28 to 37 days
  • Range age at sexual or reproductive maturity (female)
    257 to 395 days
  • Average age at sexual or reproductive maturity (female)
    343 days
  • Range age at sexual or reproductive maturity (male)
    260 to 411 days
  • Average age at sexual or reproductive maturity (male)
    330 days

Triatoma dimidiata shows no parental investment in its young. (Zeledon, et al., 1970a)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

The lifespan of Triatoma dimidiata varies by sex and seems to be independent of whether or not the individual is infected with Trypanosoma cruzi, the agent of Chagas' disease. The average lifespan of T. dimidiata females is about 662 to 789 days in laboratory settings. For infected males, the average lifespan is 610 to 689 days in laboratory settings. The maximum lifespan for this species is 3 years. (Zeledon, et al., 1970a)

  • Range lifespan
    Status: captivity
    3 (high) years
  • Typical lifespan
    Status: captivity
    610 to 789 days

Behavior

Triatoma dimidiata is a primarily nocturnal species, and has eyes that are well-developed for low light conditions. Like other Triatomines, T. dimidiata is stimulated by light, odor and movement of potential prey. During the day, T. dimidiata normally stays inside refuges, but at night, it flies out in search of a blood meal. This species is attracted to warmth and to light, both of which help explain the existence of domestic T. dimidiata. A few studies have shown that females are usually more attracted to light than males. They usually fly around light sources, such as light bulbs in homes, until they are shut off, and they then find a new refuge in the wall of the house. (Rebollar-Tellez, et al., 2009)

Home Range

Exact home range for Triatoma dimidiata is currently unknown.

Communication and Perception

Like many Triatomines, Triatoma dimidiata communicates using chemicals excreted by glands on the body. Using these pheromones, females can attract males and males can find females. The surface of their cuticle is covered in lipids that can be used for communications with other individuals.

Triatoma dimidiata perceives the environment using antennae that are located laterally on its head. It also visually interprets the environment using its eyes, also located laterally on its head. (Juarez and Fernandez, 2004)

Food Habits

Triatoma dimidiata feeds nocturnally, when its prey is sleeping. In the case of humans, the bug normally sucks blood from around the eye area. If a specific T. dimidiata is a Chagas' disease vector, this site will be the initial site of infection and will result in characteristic eye-swelling symptom of Chagas' disease, known as Romana's sign.

In many studies in which T. dimidiata were captured, they were found to not have blood in their body, meaning they had not fed in some time. This means that T. dimidiata have a high starvation tolerance, which may help them in times when blood meal sources are scarce, and it may help them in dispersal. (Coura, 2007; Rebollar-Tellez, et al., 2009)

  • Animal Foods
  • blood

Predation

Triatoma dimidiata has a variety of parasites and predators. For instance, some species of spiders eat the nymphs of T. dimidiata. Pimeliaphilus zeledoni mites parasitize all stages of T. dimidiata. There is also a type of wasp, Telenomus fariai, that grows inside the eggs of T. dimidiata. Some vertebrates are predators of T. dimidiata, such as chickens, rats, toads and lizards.

Triatoma dimidiata has developed a method of camouflage. It uses its third pair of legs to fling dirt from the ground over its bodies, causing it to blend in visually. (Zeledon, et al., 1970c)

  • Anti-predator Adaptations
  • cryptic
  • Known Predators
    • chickens (Gallus gallus domesticus)
    • rats (Rattus)
    • toads (Anura)
    • lizards (Lacertilia)

Ecosystem Roles

Triatoma dimidiata affects the ecosystem as a parasite, feeding on blood of a wide variety of animals. Triatoma dimidiata is a vector for Chagas' disease, caused by Trypanosoma cruzi, which infected Trypanosoma cruzi spread to their hosts. (Zeledon, et al., 1970d)

Triatoma dimidiata are hosts of some parasites. They are the hosts of the mite Pimeliaphilus zeledoni, which parasitize them in every stage of development. They are also hosts to the wasp Telenomus fariai, which grow inside their eggs. (Zeledon, et al., 1970c)

Species Used as Host
Commensal/Parasitic Species
  • mites (Pimeliaphilus zeledoni)
  • parasitic wasps (Telenomus fariai)

Economic Importance for Humans: Positive

While most economic effects regarding Triatoma dimidiata are negative, jobs are created to help control the insect. Professionals are hired to spray insecticide in households to remove the insects and prevent the spread of Chagas' disease. Insecticide companies also benefit since their product is purchased and utilized in homes. Specialized treatment of Chagas' disease also creates a larger job market for doctors, and medical supply companies benefit as well. (Castillo-Riquelme, et al., 2008)

Economic Importance for Humans: Negative

There are many negative economic effects that Triatoma dimidiata has on humans, all regarding preventing or treating Chagas' disease. One way the bug affects humans is the cost of spraying insecticide in houses, which kills Triatoma dimidiata and prevents them from spreading Chagas' disease to the humans or animals living in the household. Costs include paying for the insecticide and compensating the extermination professionals.

Another cost for humans involving Triatoma dimidiata and Chagas' disease is the treatment of humans already infected with the disease. The best treatments of the disease can cost several thousand United States dollars. (Castillo-Riquelme, et al., 2008)

Conservation Status

Currently there is no concern regarding the conservation of Triatoma dimidiata. As they are effective vectors of human disease, all efforts are focused on reducing population numbers. However, current extermination methods are not very successful and population numbers remain high.

Contributors

Gregory Schmitz (author), University of Michigan-Ann Arbor, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Rachelle Sterling (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

induced ovulation

ovulation is stimulated by the act of copulation (does not occur spontaneously)

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sanguivore

an animal that mainly eats blood

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

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Coura, J. 2007. Chagas disease: what is known and what is needed - a background article. Memorias Do Instituto Oswaldo Cruz, 102: 113-122.

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Juarez, M., G. Fernandez. 2004. Cuticular hydrocarbons of triatomines. Comparative Biochemistry and Physiology, 147/3: 711-730.

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Mello, F., J. Jurberg, J. Grazia. 2009. Morphological study of the eggs and nymphs of Triatoma dimidiata (Latreille, 1811) observed by light and scanning electron microscopy (Hemiptera: Reduviidae: Triatominae). Memorias Do Instituto Oswaldo Cruz, 104/8: 1072-1082.

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Zeledon, R., V. Guardia, A. Zuniga, J. Swartzwelder. 1970. Biology and Ethology of Triatoma dimidiata (Latreille, 1811) I. Life cycle, amount of blood ingested, resistance to starvation, and size of adults. Journal of Medical Entomology, 7/3: 313-319.

Zeledon, R., V. Guardia, A. Zuniga, J. Swartzwelder. 1970. Biology and Ethology of Triatoma dimidiata (Latreille, 1811) II. Life span of adults and fecundity and fertility of females. Journal of Medical Entomology, 7/4: 462-469.

Zeledon, R., G. Solano, J. Swartzwelder. 1970. Sources of Blood for Triatoma dimidiata (Hemiptera Reduviidae) in an Endemic Area of Chagas' Disease in Costa Rica.. The Journal of Parasitology, 56/1: 102.

Zeledon, R., G. Solano, A. Zuniga, J. Swartzwelder. 1973. Biology and Ethology of Triatoma dimidiata (Latreille, 1811) III. Habitat and blood sources. Journal of Medical Entomology, 10/4: 363-370.

Zeledon, R., J. Ugalde, L. Paniagua. 2001. Entomological and Ecological Aspects of Six Sylvatic Species of Triatomines (Hemiptera, Reduviidae) from the Collection of the National Biodiversity Institute of Costa Rica, Central America. Memorias Do Intituto Oswaldo Cruz, 96/6: 757-764.

Zeledon, R., C. Valerio, J. Valerio. 1970. Enemies of Triatoma dimidiata Latreille, 1811 in an endemic area of Chagas' disease in Costa Rica (Hemiptera, Reduviidae). Journal of Medical Entomology, 7/6: 722-724.