DENSITY ESTIMATES OF THE DOMESTIC VECTOR OF CHAGAS-DISEASE, RHODNIUS-PROLIXUS STAL (HEMIPTERA, REDUVIIDAE), IN RURAL HOUSES IN VENEZUELA

We report the use of the timed manual method, routinely employed as an indicator of the relative abundance of domestic triatomine bugs, to estimate their absolute density in houses. A team of six people collected Rhodnius prolixus Stal bugs from the walls and roofs of 14 typical palm-leaf rural houses located in Cojedes, Venezuela, spending 40 minutes searching in each house. One day after these manual collections, all the houses were demolished and the number of triatomine bugs were identified by instar and counted. Linear regression analyses of the number of R. prolixus collected over 4 man-hours and the census counts obtained by house demolition indicated that the fit of the data by instar (stage II - adult) and place of capture (roof versus palm walls versus mud walls) was satisfactory. The slopes of the regressions were interpreted as a measure of ''catchability'' (probability of capture). Catchability increased with developmental stage (ranging from 11.2% in stage II to 38.7% in adults), probably reflecting the increasing size and visibility of bugs as they evolved. The catchability on palm walls was higher than that for roofs or mud walls, increasing from 1.3% and 3.0% in stage II to 13.4% and 14.0% in adults, respectively. We report, also, regression equations for converting field estimates of timed manual collections of R. prolixus into absolute density estimates.