and allowed to 14–21 days
following eclosion prior to their use in this study
(FAO, 2004). Hatching tubes with the highest larval
eclosion rate (90–100%) were selected and placed in
the base of a bottle, inverted in the centre of a Petri
dish that was subsequently filled with water, which
prevented their escape. A sample of the larvae from
this tube was put in the centre of a sheet of white
paper, fixed to the bench with adhesive tape and thirty
or more specimens with good mobility caught with a
no. 4 paintbrush moistened in test solution, then gently
transferred to each envelope (Fig. 1C). The remaining
larvae on the paper were killed by squashing them
under adhesive tape.