Sally B. Patterson
Spiders use silken draglines that serve as parachutes or “balloons” to help them remain airborne as they take off for new territory — perhaps over distances as great as hundreds of kilometers. Because the insect-eating creatures could play an important part in natural agricultural pest control, it would be helpful for researchers to understand how far they travel and what affects their dispersion.
Scientists at Rothamsted Research Ltd. in Harpenden, UK, have reported research in which they have tracked spiders in action and also have developed synthetic models made of a diode attached to a silk thread that simulate spider locomotion. An important aspect of the work is that, unlike previous studies of spider travel, it factors in the effects of a flexible rather than a static dragline. The team intends to use the data to calculate the aerodynamic forces on the moving silken trail to help simulate real flight or float paths and to determine how far arachnid aerialists can maneuver.
Spiders are leaping from a grass seed head. They use a silken filament to help them stay airborne as they soar off to new territory. Spider migration can be important to natural agricultural pest control. Image courtesy of Rothamsted Research Ltd.
The researchers are studying the spiders and models in a standard wind tunnel and in a special tunnel outfitted with light detectors that trigger the release of a spider and clock its fall. Canon flashgun cameras record start and stop times when the model breaks a light beam boundary.
The models show promise as devices that can simulate ballooning behavior. However, they are limited in that they do not account for such postural variations as leg positioning and flexion, which could influence drag and landing patterns. They also are heavier than the average spider pilot. When these issues are resolved, the scientists hope to conduct radar-based field trials that will end the suspense about spider suspension.
- A two-electrode device with an anode and a cathode that passes current in only one direction. It may be designed as an electron tube or as a semiconductor device.
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