Effects of structural heterogeneity of a laboratory arena on the movement patterns of adult Eriopis connexa and Hippodamia variegata (Coleoptera : Coccinellidae)

We asked if the structural heterogeneity of a laboratory arena differential ly affected the abandonment of the plot, residence time, locomotory rate, p ause duration and turning rate of adult Eriopis connexa and Hippodamia vari egata (Coleoptera: Coccinellidae). We simulated an increase in heterogeneit y by distributing vertically-oriented toothpicks in a circular arena: one c ontrol (without toothpicks), one uniform plot (toothpicks every 1 cm) and o ne random plot (randomly distributed toothpicks). No food was provided insi de the arena. Coccinellids were released individually in the centre of each plot and their movement was videotaped. Fewer H. variegata adults left the plots as these became more heterogeneous. E. connexa did not discriminate between plots in their residence time, but H. variegata remained longer in the uniform and longest in the random plots. H. variegata only stayed longe r than E. connexa in the random plots. This resulted because adults of H. v ariegata were stationary for longer periods, moved more slowly and less lin early and explored a higher number of toothpicks than adults of E. connexa in more heterogeneous environments. Thus, the physical structure of the env ironment differentially affects the movement patterns of insects. Eriopis c onnexa seems to be less sensitive to structural heterogeneity than H. varie gata.