People with extreme fear of spiders crawling, peaking from the window and plainly gracing their sights now have another reason to tremble - a type of spider can also fly. With this, the arachnids have been included in the list of typically non-flying insects that can set itself in mid-air.

Study authors Robert Dudley, a professor of integrative biology at the University of California and Stephen Yanoviak, a biology professor at the University of Louisville have been investigating gliding insects settling in tropical forests for more than 10 years. They found that a group of ants have the ability to consistently land on a tree when it was accidentally sweep off.

The Selenopid spiders also became part of their study as scientists were baffled as to what will happen to these species should they fall from the trees of their rainforest habitats. The researchers then discovered that these spiders used directed aerial descent, which became of particular interest to Dudley. According to him, controlled gliding may be the roots of flying because these creatures learned how to use their arms and legs to glide and thus gain lift to moving in freefall. "This type of aerial behavior preceded the origin of wings," he said.

The study, published in the journal Interface by the Royal Society, involved 59 Selenopid spiders that can all cope well with skydiving. But just how can these insects glide itself while in mid-air?

The scientists found that the spiders were very flexible and "wafer thin," and it can move through the air by spreading its legs liberally so that it can utilize lift and drag to drive itself in the direction of the tree trunk when they land. In cases when they fall upside down, these creatures have the ability to correct it while in mid-air. The scientists were even able to observe that that on occasional times, the spiders can bounce off the trunk, regain composure and move back to the trunk so that it can finish off with a successful landing.

Generally, these types of spiders are the indicators of an outstanding evolutionary phenomenon in the animals' search of the air. The findings of the study pave the way for the scientists to ask for more questions related but are outside the scope of the study. While the results were able to identify the mechanisms used by the insects to "fly," the authors acknowledged that further investigations are warranted to establish the role of visual cues, leg positioning and spines in the overall aerodynamic capabilities of the spiders.

Photo: Michael Wifall | Flickr