Triatomines bugs are holometabolous insects that are essentially found in central and South America. They are responsible for the transmission of American Trypanosomiasis (also known as Chaga’s disease).
Life Cycle of Triatomine Bugs
Triatomine bugs have incomplete metamorphosis, which means that the young and the adults are similar in appearance. The life cycle is somewhat similar among species although some variation occur depending on the geographical location and environmental conditions (reference). There are 3 stages in the developmental cycle of triatomine including eggs, nymphs and adults. There are generally five nymphal instars and each instar appears after molting. Nymphs resemble to adults but can be easily distinguished by their smaller eyes and their lack of wings.
In general female mate 2 to 3 days after the final molt and eggs are generally laid withing a month after mating. Each female is capable of laying up to 30 eggs during the oviposition period but may produce up to 1000 eggs during her lifetime (). For female a blood meal is necessary for the production of fertile eggs and mating generally occur after such blood meal.
Male may mate without having fed on blood meal but if they do, they mate with fed females (reference). Eggs typically hatch between 10 and 37 days after oviposition (). After emergence, nymphs take their first blood meal within 72 hours, and blood feeding is necessary for molting to the next nymphal instar. The duration of the life cycle range from 4 to 24 months and varies among the species (reference). Host availability and environmental conditions are the key determinants of the life cycle of triatomine bugs. One striking fact about triatomine bugs is their ability to survive for several months without a blood meal. When a host become become available they can feed intermittently every 4 to 9 days ().
Ecology of Triatomine Bugs
From ecological standpoint, kissing bugs can be divided into 3 groups including domestic, peridomestic and sylvatic species. Domestic species colonize human habitation and depend almost exclusively on human for acquiring blood. This is the case case of Triatoma infestanswhich depend on humans and domestic animals for acquiring blood meal. Peridomestic species rely on on domestic animals such as chicken and live almost exclusively in the enclosure of such animals. Sylvatic species of triatomines live exclusively in the wild where they live in the habitats of various vertebrates including amphibians, lizard, rodents, opossums armadillo, sloths, bats and many others.
There is no separation between the different ecological categories as a domestic species may be carried in the wild and may be able find a suitable host there. Similarly a sylvatic species may be able to survive and adapt in a domestic and peridomestic environment. Finding a suitable host is generally what determine the survival of a triatomine species in an environment. Some species such as Rhodnius prolixus lay their eggs on palm fronds that are use as roof for human habitations. This passive transport constitute the source of primary infestation in domestic and peridomestic environments.
Triatomine are very secretive and most species are only active during night time while people are sleeping. During the day, they tend to hide in cracks and crevisse. Young and adults of triatomine bugs occupy the same habitat and only different in size. Triatomine species that transmit trypanosomiasis to humans are adapted to living in or near houses where they can target human and domestic animals (such as chicken, cattle, dogs, or cats) (reference) while they are sleeping. The feeding time and frequency depend on the species and favorable conditions. For most triatomine bugs species feeding time vary between 10 to 25 minutes (references).
Triatomine bugs are active during the night and feed on their host while they are sleeping. Some species of may also feed during the day but in general these insects prefer to rest in crack and crevices in home structures typically dark and difficult to spot (reference). The fact that these insects occur in poor area with mediocre living conditions contribute to provide breeding conditions. Some species of triatomine dwell around houses and only move into homes to engorge and get out of there as fast as they can.
What attract kissing bugs to humans and other hosts?
Heat and chemical cues are essentially the factors that alert kissing bugs for the presence of a probable host. In Rodhnius prolixus heat receptors located on the antennae stimulate the insect for probing activity. Carbon dioxide also seems to increase the activity of kissing bugs in finding their hosts. After successful feeding on a suitable host, triatomine bugs defecate on their host. It is also suggested that pheromone that may be contained in the feces of nymphs and adults of Triatoma infestans alert other on the presence of a good host ().