Abstract:
A ten-point visual method of estimating the abundance of immature blackflies in the field is proposed and tested.
The method is based on the comparison of larvae and pupae found on natural substrates, with ten diagrammatically
prepared abundance classes. When estimates were based on the abundance of blackflies within a 4 x 4 cm area
of highest density, there were no significant differences between estimates based on the ten-point visual method
and those based on actual counts (P > 0,05). The time taken to assess the abundance of larval blackflies on 30
substrates was about 15 min, depending on substrate accessibility. Personal bias was assessed independently
by four people, and was negligible when estimates were based on the highest densities within a 4 x 4 cm quadrat.
The method tends to overlook very small larvae, and is not recommended for estimating overall population
densities. However, the method provides a reliable, practical and rapid index of blackfly abundance suitable for use
in blackfly control programmes.
