Determining the LC99 of Fipronil. The protocol we
selected for detecting resistance called for treating
adult males with the LC99 of Þpronil. An estimate of
this value was therefore needed and was obtained by
analyzing the relationship between insect mortality
and Þpronil dose with adult males of the insecticidesusceptible
strain. Ten concentrations of Þpronil,
ranging from 1.5 to 3.2 ng per insect, were administered
topically to males, and killed between 3and 97%
of them in 72 h. A logit model (Table 2) was Þt to the
data and predicted the LC99 to be 3.3 ng per insect.
The 95% conÞdence interval of this estimate, 3.0 Ð3.6