Reproductive summer butterflies fail to consistently show directional flight. (A) Virtual flight paths of the individual summer butterflies tested (n = 18, black lines), vehicle-treated migrants (V-Migrants; n = 18, blue lines; 12 directional [from Figure 2A]/6 non-directional) and methoprene-treated migrants (M-Migrants; n = 12, red lines; 10 directional [from Figure 2A]/2 non-directional) flown in flight simulator. The summer butterflies were housed under simulated summer conditions in a light-dark cycle with lights on from 0430 to 1900 hours EST at 20°C for at least three days before being tested outdoors in a flight simulator (flown between 1230 and 1530 hours). Virtual flight paths were constructed by starting in the center of the square and plotting each direction interval consecutively as one unit length . (B) R-values for individual virtual flight paths shown in (A). R-values differed among summer, vehicle-treated migrants and methoprene-treated migrants (p = 0.005). Tukey's pairwise comparisons revealed that summer butterflies had lower r-values than vehicle- and methoprene-treated migrants. (C) Flight orientation of summer butterflies. Of the 18 summer butterflies flown in the flight simulator, only five showed significant directional flight. The large circles represent the 360° of possible direction (0° is north), with the small solid circles on the perimeter representing mean orientation for an individual flight.
Zhu et al. BMC Biology 2009 7:14 doi:10.1186/1741-7007-7-14