"Spider ballooning is a relatively common seasonal event that occurs in the spring and fall months," says spider expert Allen Dean of Texas A&M University. "Normally this occurs in Texas in May and September. Apparently September's peak was delayed this year until cooler conditions prevailed."

"Spiders use their silk as a way to disperse," said Dean. A variety of spiders use their silk as a simple parachute to carry them from one place to another. Light winds and rising thermals favor spider dispersal in this manner. The spider stands facing the air current from the top of a grass blade or other platform. Then, standing on tip-toe and with its abdomen pointed toward the sky it releases a stream of silk from its spinnerettes. When the wind currents catch the threads the spiders release their lauching pad and off they go.

Normally it is the smaller adults and immatures of larger species that balloon. When millions of spiders are doing this at the same time it is not unusual for flying silk to become noticeable on lawns, trees, and even getting caught in hair.

Despite the logical scientific explanation, people never cease to speculate about the origins of the mysterious floating threads. According to Dean, during WWII large mats of orange sheets fell from the sky leading people to think they were experiencing some new type of biological warfare. Callers to Texas A&M following 9/11 wondered if the silken threads adorning trees were all part of some vast terrorist plan.

The simple explanation does not take away from the amazing ingenuity of spiders in their quest to spread and colonize new sites. The nineteenth century naturalist Charles Darwin noted ballooning spiders landing on ship up to 60 miles off the coast of South America. Modern biologists have collected spiders floating on air currents at altitudes over 10,000 feet.

For more information about spiders around the home and their control, see http://tcebookstore.org/pubinfo.cfm?pubid=252