This is the presentation of data obtained by a study carried out in the Northeast of Brazil, where the biogeographical characteristics include the "caatinga" (a semi-arid) savanna and ample transitional strips with other features. Among them are the Atlantic tropical forest and the larger forest inclusions. From 1975 to 1980, a total of 15,342 bugs collected in domiciliar environment were examined to discover the blood feeding habits of and natural infection by Trypanosoma of the cruzi type. Intestinal content was submitted to reactions to antiserums for humans, dogs, cats, rodents (Rattus), opossums (Didelphis), and birds (Gallus). By order of frequency, the species found were: Triatoma pseudomaculata (40.6%). Panstrongylus magistus (19.7%), Triatoma brasiliensis and T. sordida (14.3% each), Rhodnius nasutus (6.1%) and Triatoma infestans (1.1%), and some other rare ones. Blood was detected in 42.4% and the infection rate was 3.4% of the total of the specimens examined. High feeding mobility was observed, and the general blood containing rates were 54.8% for birds and 30.0% for humans. P. megistus showed considerable anthropophily and was followed, at a lower degree, by Triatoma brasiliensis. Ornitophily was detected at high level among T. pseudomaculata and T. sordida, while R. nasutus fed almost exclusively on this host. On the other hand, the presence of human blood in specimens collected in peridomiciliar dwelling places indicates frequent spacial mobility, which occurs after the bugs have had their blood meals. This was quite evident among all the species except T. infestans which thus showed no tedency for displacement from this environment. Domiciliarity was also evident among P. megistus and, to a lower degree, among T. brasiliensis, T. pseudomaculata and T. sordida. However, domiciliarity was not characteristics of R. nasutus. Information on geographical distribution confirms the autochthonous quality of T. brasiliensis, T. pseudomaculata and R. nasutus populations in the "caatinga". The same autochthonous feature was evident in the P. megistus with relation to the Atlantic and inclusion forest environments. Nevertheless, it seems that this last triatominae bug becomes invasive in the "caatinga"; moreover similar patterns were evident for T. infestans and T. sordida in all the Northeast region studied. Results permit the conclusion that, in the regional epidemiological transmission of South American trypanosomiasis, P. megistus play an important role, followed, in this particular aspect, by T. brasiliensis. Depending on several factors, probably colonization density, T. pseudomaculata and T. sordida may come in second in this aspect. For the present, T. infestans low density in the region presents only potential risk. Routine control through the application of domiciliary chemicals will break transmission. However, at least in the peridomiciliary environment, reinfections by P. megistus will continue to occur in the forest regions, and T. brasiliensis, T. pseudomaculada and R. nasutus in the savanna "caatinga". Probably this will be due to natural foci that will supply the human environment. Therefore, epidemiological surveillance must to take these several aspects into account and to increase its efficiency by research development.
Triatominae; Food habits; Natural infection; Distribution; Domiciliation; Ecology