Inter-Individual Variation and Consistency in Walking Behavior of the Rose Aphid, Macrosiphum rosae (Hemiptera: Aphididae)

Abstract

Variations in morphological and behavioral properties of animals are generally considered as evolutionary adaptations to unpredictable environments. At the same time, individuals may present a strong consistency in their expressed behavior. In this study, we investigated inter-individual variations and consistency in walking behavior of both apterous and winged morphs of the rose aphid, Macrosiphum rosae (L.) (Hemiptera: Aphididae). Adult apterous and winged aphids were released three times on the surface of a corn leaf cut (40 cm × 5 mm) and the time elapsed and the numbers of steps walked by individuals to go through it were recorded. Although, our results revealed a strong consistency in walking speed of both apterous and winged individual aphids, we found a wide variation in walking speed of different individuals for these morphs. These variations were predominantly associated with the differences in the number of steps walked by individual aphids, and less importantly, to their walking speed. Altogether, winged aphids walked with a higher average speed than apterous ones (42.42 vs. 38.92 cm min−1, respectively) (P < 0.01). This may be an evolutionary adaptation of winged aphids where they should walk actively to find a suitable site for establishment after an unpredictable air-borne flight. We measured the wet body weight of apterous and winged adults to find a correlation between body weight and walking speed. Although, the winged aphids were significantly lighter than apterous ones (P < 0.01), we found no reliable data to correlate the observed variations in walking behavior of rose aphids to their body weight. The importance of this inter-individual variation in the evolutionary biology of clonal aphids has been discussed.