Abstract
Some small spiders fly in the air by means of their spinned long threads which are dragged by a ascending current. The spider may take off the ground when the upward component of the net drag force excerted on the thread exceeds its weight. In a uniform wind, it eventually travels at a constant velocity with its thread stretched vertically straight.
The fine thread is very effective to capture the lifting force because of its small local Reynolds number and mass. It is also so flexible that it serves as a mass-less medium to transmit the tensile force along itself to suspend the massive spider. The physics underlying the deformation of thread is formulated in order to numerically simulate the transient process of spider's flight from its take-off to steady flight. Experiments using liquid in place of air are conducted for the measurement of required drag law and for comparison with numerical results.
