Studies on the deposition of oil drops

SUMMARY At low wind speeds of up to 4 m.p.h. in a horizontal tunnel, deposition of air‐borne oil droplets, up to 60 μ in diameter, occurred more readily on tsetse flies at rest on obstacles representing approximately the shapes of branches and leaves than on the obstacles themselves. Under some conditions deposition occurred on all flies irrespective of resting position, although the obstacle remained completely free from deposit. At 1 m.p.h. deposition was largely by sedimentation; at higher wind speeds it was largely by impaction. The optimum drop‐size range for deposition on tsetse flies at rest on the obstacles appeared to be from 10 to 30 μ. Deposition of these drops by impaction on the obstacles themselves, however, was less than that of larger drops.