2024 Volume 39 Issue 1 Pages 1-5
We observed the numbers of redback spiderling individuals that passed the baseline and that floated in a transparent pipe with no wind and with an upward wind (1.7 m/s), and recorded them over time. Spiderlings newly emerged from the egg sac did not show active movement even under windy conditions, but during the dispersal period, the number of downward baseline crossings under windy conditions was significantly higher than under windless conditions (Wilcoxon signed-rank sum test, n=8, p=0.012). In addition, when we observed the spiderlings’ floating posture with a high-speed camera, we found that they fell with the cephalothorax facing down in a “レ” shape, and when exposed to the wind, they spread their legs and floated. This is different from “ballooning”, and we saw no evidence of ballooning in redback spiders in this experiment.
