The Analysis and Description of Movement in Adult Danaus Plexippus L. (Lepidoptera: Danainae)

[1. Interactions among flying butterflies, Danaus plexippus, and various densities and dispersions of their milkweed food-plants, Asclepias spp., have been studied using a continuously recording tracking device. 2. Study areas comprising within-patch and edge plants and areas with no plants were not treated uniformly by the butterflies. Regions with plants were visited more frequently than those without and the greatest range of behavioural activities, basking, feeding and ovipositing, occurred about the plants themselves. There was also a geographical bias in usage by both sexes. 3. Distributions of straight line headings of butterfly tracks (i.e. lines joining the first and last points of a recorded track) did not differ from uniformity for either males or females. 4. Incident angles for females but not for males were significantly biassed geographically. 5. Males divided their time equally between flying and pausing and their pauses were made up equally of feeding and basking. 6. Females spent 25% of their time flying and 75% pausing, these pauses comprising approximately 75% basking, 10% egg-laying and 15% feeding. 7. Transitions between particular behavioural states were not all equally likely for females. An oviposition was most likely to be followed by another oviposition or basking; a bask by an oviposition. 8. The mean vectors of tracks in the horizontal plane based on an analysis of 0.75 s fixes along the continuous tracks had a mean direction (R1) of 0.37 for males and 0.22 for females with associated mean angle (ζ values of 0.98 and 1.04 respectively (statistics after BATSCHELET, 1965). 9. There was much less movement in the vertical plane with a mean absolute angle of turn of 8.5° (SD = 13.75) for males, and 12.9° (SD = 19.64) for females. 10. Speed of movement based on the distances moved between successive fixes was 2.38 m/s (SD = 1.15) for males and 1.43 m/s (SD = 0.54) for females. Males moved significantly faster than females. 11. The signs of angles turned through (i.e. left hand vs right hand turns) in successive segments of track were independent both at the first order (two segments) and third order (three segments) level, in both sexes. 12. Move lengths showed significant differences from homogeneity at both first and second order level when the moves were classified as above or below average for each sex. 13. Both sexes were more directional and faster when flying in the open than when within patches of food-plants. Differences in directionality among patch edge, patch centre, and single plant situations occur. The distribution of angles turned through is centred on 0° for males in all areas and is bimodal about 0° and ± 180° for females. This difference between sexes is ascribed to specific, food-plant related activities on the parts of the females. Other minor differences in flight patterns in different parts of the study area are noted. 14. The results of this work are used to draw up the 'rules of movement' for male and female adult D. plexippus and the biological significance of these rules for the resulting patterns of movement and resource usage are discussed., 1. Interactions among flying butterflies, Danaus plexippus, and various densities and dispersions of their milkweed food-plants, Asclepias spp., have been studied using a continuously recording tracking device. 2. Study areas comprising within-patch and edge plants and areas with no plants were not treated uniformly by the butterflies. Regions with plants were visited more frequently than those without and the greatest range of behavioural activities, basking, feeding and ovipositing, occurred about the plants themselves. There was also a geographical bias in usage by both sexes. 3. Distributions of straight line headings of butterfly tracks (i.e. lines joining the first and last points of a recorded track) did not differ from uniformity for either males or females. 4. Incident angles for females but not for males were significantly biassed geographically. 5. Males divided their time equally between flying and pausing and their pauses were made up equally of feeding and basking. 6. Females spent 25% of their time flying and 75% pausing, these pauses comprising approximately 75% basking, 10% egg-laying and 15% feeding. 7. Transitions between particular behavioural states were not all equally likely for females. An oviposition was most likely to be followed by another oviposition or basking; a bask by an oviposition. 8. The mean vectors of tracks in the horizontal plane based on an analysis of 0.75 s fixes along the continuous tracks had a mean direction (R1) of 0.37 for males and 0.22 for females with associated mean angle (ζ values of 0.98 and 1.04 respectively (statistics after BATSCHELET, 1965). 9. There was much less movement in the vertical plane with a mean absolute angle of turn of 8.5° (SD = 13.75) for males, and 12.9° (SD = 19.64) for females. 10. Speed of movement based on the distances moved between successive fixes was 2.38 m/s (SD = 1.15) for males and 1.43 m/s (SD = 0.54) for females. Males moved significantly faster than females. 11. The signs of angles turned through (i.e. left hand vs right hand turns) in successive segments of track were independent both at the first order (two segments) and third order (three segments) level, in both sexes. 12. Move lengths showed significant differences from homogeneity at both first and second order level when the moves were classified as above or below average for each sex. 13. Both sexes were more directional and faster when flying in the open than when within patches of food-plants. Differences in directionality among patch edge, patch centre, and single plant situations occur. The distribution of angles turned through is centred on 0° for males in all areas and is bimodal about 0° and ± 180° for females. This difference between sexes is ascribed to specific, food-plant related activities on the parts of the females. Other minor differences in flight patterns in different parts of the study area are noted. 14. The results of this work are used to draw up the 'rules of movement' for male and female adult D. plexippus and the biological significance of these rules for the resulting patterns of movement and resource usage are discussed.]