Relationship Between Wing Loading, Wingbeat Frequency and Body Mass in Homopterous Insects

Several biophysical properties of members of Aleyrodidae and Aphididae were examined in order to explore how homopterous insects fly. Five species of aphids were found to weigh significantly more than five whitefly species (range 1.14-7.02xl0⁻⁴g for aphids vs 3.3-8.0x 10⁻⁵g for whiteflies) and to have significantly larger wing surface areas (range 0.0103-0.1106 cm²vs 0–0096-0.0264cm²). As a consequence whiteflies and aphids can be partitioned into two groups with respect to wing loading (range 0.00633-0.01412 gcm⁻² for aphids, 1.74-5.23x 10⁻³gcm⁻² for whiteflies). Members of the two families are also separated in terms of wingbeat frequency (range 81.l-123.4Hz for aphids, 165.6-224.2 Hz for whiteflies). Since our animals were much smaller than any insects examined previously for these parameters, values were compared with the same parameters for 149 insect species recorded in the literature. Using these data, we found wingbeat frequency to be significantly correlated with wing loading only in insects weighing more than 0.03 g. Larger insects seem to employ a strategy similar to other flying animals, by compensating for high wing loading with higher wingbeat frequencies. The lack of correlation for these two parameters in insects weighing less than 0.03 g probably results from the use of different flying strategies. These include employment of a clap and fling mechanism and the possession by some of exceedingly low wing loading. Also, small insects may have reduced settling velocities because they possess high drag coefficients. Previous studies which failed to establish a relationship between wing loading and wingbeat frequency in larger insects may have considered too few subjects or too great a range of body masses. The mass range is important because smaller insects which employ increased wingbeat frequency must use rates exponentially higher than those of larger insects utilizing the same strategy.