Preliminary studies on temperature selection and activity cycles of Triatoma infestans and T. spinolai (Heteroptera:Reduviidae), Chilean vectors of Chagas' disease.

Preferred temperature and activity patterns of Triatoma infestans Klug and Triatoma spinolai Porter were studied, both are vectors of Chagas' disease in Chile. In the laboratory, 24 T. spinolai and 18 T. infestans were exposed to a temperature gradient between 50 and 15 degrees C and a photoperiod of 14:10 (L:D) h. Temperature and hourly position of bugs in an experimental chamber were recorded for 24 h. Both species showed a cycle of preferred temperature, and both selected higher temperatures beginning at 1600 hours, although T. infestans maintains this preference over a longer period. For both species, activity patterns were synchronized with the light-dark cycle, although these activity rhythms were significantly different. T. spinolai had higher activity during the photophase, and T. infestans showed a lower activity in the photophase and a higher one during the scotophase. The similar pattern of preferred temperatures may facilitate the selection of similar environments in the event of colonization of houses by T. spinolai. Diurnal activity of this species might be a disadvantage (in terms of more exposure to defensive responses of the vertebrate hosts) but may allow T. spinolai to share the same habitat with T. infestans without competitive interference.