ARTICLE Interactions Between Triatoma infestans and Triatoma sordida (Hemiptera: Reduviidae) in Artificial Ecotopes: Population Growth and Age Structure ELENA B. OSCHEROV, 1 MIRYAM P. DAMBORSKY, 1 MARIA E. BAR, 1 GILBERTO AVALOS, 1 BENEDICTA M. ALVAREZ, 1 HILDA PRESMAN 1 AND CRISTINA WISNIVESKY-COLLI 2 J. Med. Entomol. 38(2): 214Ð217 (2001) ABSTRACT Interaction characteristics between Triatoma infestans Klug, 1834 and Triatoma sor- dida Stål, 1859 populations were studied in artiÞcial ecotopes for 16 mo. The experimental design involved simultaneous treatments with T. infestans and T. sordida together in the same experimental unit (EU) and each separately in two control units (CU) made of adobe bricks. Chickens were used as host animals. Each unit was dismantled monthly to estimate triatomine population size and age structure, rebuilt, and repopulated with the same insects. In both units, T. infestans population growth followed a logistic model, whereas T. sordida did not show this pattern. T. infestans completed a generation in 24 wk (EU) and 32 wk (CU 1 ), whereas T. sordida did not complete one generation during this period. We concluded that T. infestans showed a better colonizing success than T. sordida. After living together for 1 yr, an interference process took place that resulted in the extinction of T. sordida. KEY WORDS Triatoma infestans, Triatoma sordida, interspeciÞc competition Triatoma infestans KLUG, 1834 and Triatoma sordida Stål, 1859 are the most abundant triatomines in the Province of Corrientes, Argentina. The former is the only domiciliary vector of Trypanosoma cruzi Chagas, 1909 in this country. Although T. sordida occurs pri- marily in sylvatic biotopes, it is often found in peri- domestics ecotopes and is also able to invade houses and establish domestic colonies (Bar et al. 1992, 1993; Wisnivesky-Colli et al. 1993; Bar et al. 1996, 1997). The temporary elimination of T. infestans as a result of chemical control provides an empty niche for T. sordida (Salvatella 1986, Dias 1988, Diotaiuti 1991). This ecological succession is favored by the environ- mental disturbance produced by humans because de- struction of natural shelters could result in sylvatic triatomines looking for a more suitable habitat (Dio- taiuti et al. 1995). Notwithstanding, the persistence of T. infestans col- onies in peridomestic ecotopes after insecticide treat- ment facilitates domiciliary recolonization. Therefore, the simultaneous invasion of houses by T. infestans and T. sordida from extradomestic ecotopes may take place. It appears that the one with greater capability to exploit available food resources and to increase in abundance will colonize the human dwellings. In a previous study, Bar et al. (1994) experimentally found that when T. infestans and T. sordida colonized an artiÞcial ecotope at the same time, T. sordida be- came extinct. That could have been due to either competitive exclusion or to its inability to adapt to the experimental system employed. To explore this hypo- thetical situation, we studied the interactions between T. infestans and T. sordida populations living together in an experimental model. Materials and Methods The studies were carried out on T. infestans and T. sordida populations that were maintained in three artiÞcial units that simulated a poultry coop, during a 16-mo period from April 1995 to December 1996. The initial composition of each population corre- sponded to a calculated stable age distribution com- posed of 116 eggs, 82 Þrst instars (N1), 48 second instars (N2), 16 third instars (N3), 11 fourth instars (N4), 19 Þfth instars (N5), six males and six females as calculated by Rabinovich (1972) for T. infestans. These triatomines were the Þrst offspring of females cap- tured in rural areas. Each unit measured 0.80 by 0.80 by 0.80 m and was constructed with sun-dried clay blocks and externally protected with plastic mosquito screen on a wooden frame that prevented the insects from escaping. This basic structure was similar to the one used by Gorla and SchoÞeld (1985). The use of animals involved in this study followed an ethical and appropriate protocol. The protocol was approved by our institution and is on Þle in our laboratory. 1 Ca ´ tedra de Artro ´ podos. Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste (UNNE), Av. Libertad 5470, (3400) Corrientes, Argentina. 2 Unidad Ecologõ ´a de Reservorios y Vectores de Para ´ sitos, Depar- tamento de Ciencias Biolo ´ gicas, Facultad de Ciencias Exactas y Na- turales, Pabello ´ n 2, Universidad Nacional de Buenos Aires (UBA), (1428) Buenos Aires, Argentina. 0022-2585/01/0214Ð0217$02.00/0  2001 Entomological Society of America Downloaded from https://academic.oup.com/jme/article/38/2/214/876987 by guest on 06 March 2023