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- Taxonomy lineage of Triatominae (main page)
- General information (main page)
- Genera of Triatominae family (main page)
- Panstrongylus genus (new page)
- Rhodnius genus (new page)
- Triatoma genus (new page)
- Life history (this page)
- References (main page)
Triatomines greatly vary in their life history traits; however general development steps are like this: the eggs hatch nymphs of first instars, which reach fifth instars after four molts and then, after last molting, become adult. Each stage is strictly hematophagous. At least one full blood meal is required for molting (shedding of outer cuticular layer, also called, ecdysis). Molting is followed by growing and hardening of new, bigger exoskeleton of the bug. When a nymph reaches the adult stage it may require one or more blood meals for successful copulation and oviposition of viable eggs. However, it was shown that females of some species can lay a limited number of viable eggs without prior access to food.
- Egg Female lays clutch of 6-8 eggs per week. Number of eggs laid per female's life span varies greatly and depends on species and conditions. From laying to hatching takes usually about 20 days.
Immature stage of bug. At least one blood meal (depends on species)
is required to molt and proceed to next stage.
- 1st instar N-I. Often, most vulnerable life stage of bugs.
- 2nd instar N-II
- 3rd instar N-III
- 4th instar N-IV
- 5th instar N-V. Together with adults, this stage is considered most epidemiologically important.
- Adult Life span of adult greatly depends on species and ranges from 50 to 300+ days.
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Reduviid bugs Microtomus purcis (Drury) in San Diego zoo's display. Nymphs of different stages are marked with blue arrows and adult is marked with red arrow. Microtomus purcis belongs to subfamily Microtominae within Reduviidae family, which makes it a close relative of triatomines. The species was implicated as accidental vector of T. cruzi (UNDIANO C., 1964).Back to top
Comparative timetable of life histories
The table is presented to demonstrate how life history parameters may vary among and within species.
For species represented in the table detailed data can be found in the corresponding references. Descriptions and references for other triatomine species can be found:
- Genera Belminus, Cavernicola, Dipetalogaster, Eratyrus, Linshcosteus, Mepraia, Psammolestes
- Genus Panstrongylus
- Genus Rhodnius
- Genus Triatoma
Time required for each stage to be completed is given in days.
|T. maculata||22(2)||17.8(1); 35(2)||20.8(1)||20.9(1)||24.9(1)||41.4(1); 40(2)||
|T. mexicana 2||22.7 (50%), 20.4 (75%)||37.6 (50%), 35.2 (75%)||32.1 (50%), 31.3 (75%)||39.1 (50%), 36.9 (75%)||44.5 (50%), 47.1 (75%)||112.6(50%), 115.8 (75%)||Ref.|
Various aspects of triatomines' life are studied. Researchers focus on traits that are important for assessment of bugs' potential as vectors of Trypanosoma cruzi, causative agent of Chagas disease. Below is the list of life history traits and habits of triatomines that are most important for their vectorial capacity and are most commonly reported in the literature.
History traits of triatomine bugs
- Feeding requirements prior oviposition.
- Preoviposition period (delay between last ecdysis and first oviposition).
- Number of eggs laid by female bug during its life. This parameter depends on rate of laying and adult longevity. Under laboratory conditions it was found that P. geniculatus females can lay about 62 eggs per lifetime (Cabello DR et al., 1998), whereas T. maculata females were able to lay up to 256 eggs per lifetime (Luitgards-Moura JF et al., 2005).
- Hatching rate. The hatching rate depends on mortality of embryos and proportion of unfertilized eggs.
- Duration of each stage.
- Life span of adults. For example, life span of fed females of T. barsiliensis was only about 90-120 days (Daflon-Teixeira NF et al., 2009) whereas life span of fed females of T. flavida ranges from 285 days to up to 486 days (Cabello DR, Lizano E., 2001).
- Mortality at each stage.
Feeding behavior and defecation patterns
- Host preferences when presented with choice (preference for mammals is important characteristic of vectors).
- Time before attack. Usually it takes 2-10 minutes for bug to start feeding on immobilized host.
- Duration of feeding. Usually time spent on the host while feeding increases from 1-2 minutes in earlier instars to 30 minutes and longer in 5th instars and adults. The longer is the bloodmeal, the more probable that the bug will defecate on the host or in vicinity of the host.
- Number of meals required for molting at each stage (usually from 1 to 5-6 bloodmeals are needed depending on amount of blood ingested at each meal).
- Number of bloodmeals required for optimal fertility and fecundity.
- Resistance to starvation.
- Post-feeding defecation delay. Many researchers set defecation delay of 10 minutes or less as important vectorial characteristic. Most prominent vectors defecate during feeding in up to 50% cases. For example, 58% of nymphs of Triatoma infestans produced their first defecation within five minutes after being fed (Rodríguez CS, Carrizo SA, Crocco LB., 2008).
- Amount of blood ingested at each feeding (calculated by weighting bugs before and after feeding).
- Voluntary fasting duration (period during which bug does not seek next bloodmeal).
- Locality where bugs were captured. Note differences between life history traits of R. eucadoriensis captured at different localities in Ecuador (table).
- Temperature at which experiment was conducted.
- Relative humidity during the experiment. Note differences between life history traits of T. mexicana kept at different relative humidity (table).
- Host. Usually in laboratory, bugs are fed on chicken, mice, pigeons, or hamsters. Life history traits may depend on the host, for example, species adapted to bird blood can develop slower and exhibit greater mortality when fed on mice.
- Feeding regimen (frequency of feeding). Results can vary between research studies depending on established feeding regimen in laboratory.