Figure 3. Effect of heterospecific density on the population growth of two species of stored grain beetles (Sitophilus zeamais and Rhyzopertha dominica) reared on maize grains free of insecticide residue (a) and reared on maize grains treated with 0.7 ppm of the organophosphate insecticide fenitrothion (b).

Each symbol represents the results of an experimental replicate.