Predators: Triatoma infestans and other Triatomine species
infestans is a nocturnal predator that blood feeds
on mammals while they are asleep. It is about one inch
(2.5 cm) long, has two pairs of long, bent legs attached
to an oval-shaped abdomen. A third pair of legs act
like arms that are attached to the trapezoidal thorax
near its protruding bulbous eyes. A proboscis (slender,
needle-like projection) extends from the anterior head
that is used to pierce skin and suck blood - a vampire-bug.
is yellow-orange with black marking on top of its abdomen.
are larger than females. Their wings are thin, transparent,
and cover the top of the abdomen. Only adults have wings,
which are inefficient for flying but effective for gliding
and mounting their mate during sex. Triatomines prefer
nesting in roofs and ceilings, where they glide down
upon sleeping humans. They are directed towards humans
and other warm-blooded creatures by radar-like heat
sensors in their antennas. Triatomines glide over 100
meters assisted by air currents. Gliding enables triatomines
to travel throughout communities, colonizing house after
infestans is an instinctual blood sucker. It needs
blood meals to pass through five instar stages to become
an adult when it grows wings, copulates, and reproduces.
Blood provides T. infestans with a protein- and
lipid-rich diet. Heat sensors and pheromones (hormones
deposited upon humans by previous predators) direct
T. infestans to sleeping people. Detecting a
food source, they probe the warm skin for underlying
fluids with their proboscis and sense adenosine triphosphate,
ATP, and other engorgement indicators. Coated with an
anesthetic and anticoagulant, the proboscis pierces
the skin and leisurely sucks up to 300 mg in sometimes
30 minutes. T. infestans is a glutton. After
feeding, the abdomen of the engorged bug triggers peristalsis,
and vinchucas defecate and deposit T. cruzi
in the feces at the site of the wound. T. infestans
exchange feces and parasites for blood. It ingests up
to seven times its weight and has difficulty crawling
away so slowly that awakened sleepers catch it - smashing
them and leaving a brown splotch, a telltale sign to
wary guests not to sleep there.
development of T. infestans
triatomines develop into the adult stage before males
do. After males emerge as adults, they inseminate females.
Females are inseminated shortly after molting and can
produce viable eggs for one year after copulation. In
10 to 20 days, females lay eggs. Females lay from 80
to 100 eggs, each ivory colored and half the size of
a grain of rice. Adult T. infestans live an average
of 8 to 16 months Their life span in Bolivia is 3 years
and they lay an average of 240 eggs. Their eggs are
valued by peasants who interpret them as signs of fertility.
Girls put vinchuca eggs in tiny baskets and pretend
that they are chicken eggs. Educational programs are
changing peasants' perception of vinchucas eggs.
Triatomines readily spread from the countryside to cities
by transport of vinchuca eggs unknowingly carried
pass through 5 instar or growth stages,
from birth and to adulthood. At all stages, triatomines
are fast crawlers. Nymph stages take anywhere from 4
to 24 months, depending upon the availability of blood
meals - needed to pass on to the next stage. During
these stages they are able to feed up to 12 times their
body weight. Fifth-stage instars are particularly dependent
on blood meals to transform into adults, characterized
by developing wings. Because flying takes a lot of energy,
T. infestans is efficient, developing them only
to reproduce and to colonize other areas. Triatomines
usually take their blood meals after 7 days, but are
able to live for months without feeding.
are not born with T. cruzi. As they feed throughout
their early nymph stages, they become more susceptible
to picking up T. cruzi, and incidents of infected
bugs rise with age. Many become infected by the third
instar stage. The infection rate of humans determines
the infection rate of vinchucas. The higher the
infection rate of a host population, such as in a house,
the higher the infection rate is for T. infestans.
Instars are small and superb crawlers. They hide in
mattresses and bus seats where they can bite humans.
They also crawl under mosquito netting and into sleeping
bags, making it difficult to stop them.
are nocturnal and photosensitive. They hide during the
day, coming out to feed and reproduce at night. Cracks
of walls, mattresses, and clothing provides dark safety
until nighttime, when they scurry about in search for
infestans is the species most responsible for Chagas'
disease in Bolivia, and accounts for 97% of the cases.
The remaining 3% of Chagas' disease are caused by T.
guasyana, T. melanocephala, T. oswaldoi,
and T. venosa. This latter triatomines are primarily
sylvatic and spread chagas among the wild animals it
preys on. With the depletion of wild animals and their
habitats in the Andes and Amazon, the threat of these
triatomines spreading to urban areas becomes another
America, Triatomine species responsible for Chagas'
disease are, in order of importance, Triatoma infestans,
Rhodnius prolixus, Panstrogylus megistus,
Triatoma brasiliensis, Triatoma sordida,
and Triatoma dimidiata. In Central America and
Panama, the chief vector is Rhodnius pallescans.
The primary reason for their abundance is that they
have adopted domiciliary habits.