by Lacey R. Lopez
Imagine you’re playing in the backyard with your friends, kicking around the good ol’ soccer ball. Suddenly, you feel a tickle on your cheek. “What is this?” you ask. “Are my spidey senses tingling?” You shriek in horror as you realize that there is a SPIDER.ON.YOUR.FACE. Now, don’t panic, just brush it off. After all, spiders play an important role on this space rock we call home. But this incident of mistaken landing does beg the question of how the spider got on your face in the first place.
Just like us, spiders need to get from place to place. One way spiders travel is by “ballooning”. Now, I know what you’re thinking, and no, spiders aren’t hitchhiking on hot air balloons. Ballooning is a special behavior used by some arthropods (invertebrate animals, like spiders) to journey across large distances. Spiders have furry legs with specialized hairs, called trichobothria, that sense environmental changes. To balloon, spiders stretch out their legs and stand on the tip of their spider paws, a behavior known as “tiptoeing” (Figure 1). The spiders then point their abdomens up towards the sky and release silk threads from their spinnerets. Released silk strands repel each other, like the hair on your head when you rub against a not-spider balloon (Figures 2 and 3). Then, it’s a countdown to blast off!
Spiders can’t fly, but they have been found over 2 miles high in the sky. Additionally, the renowned naturalist Charles Darwin observed hundreds of spiders that invaded his ship while he was many miles away from shore! Thus, since the early 1800s, scientists have wondered what natural forces cause spiders to balloon and become airborne. One of the primary theories was that spiders detect e-fields. E-fields are like invisible force fields generated by differences in electrical charges, such as the repulsion of charges within a storm cloud that can cause lightning.
Researchers, Erica L. Morley and Daniel Robert sought to understand how e-fields impact ballooning in spiders. In this 2018 study, researchers put Linyphiid spiders into a controlled box with a piece of cardboard that was used as a liftoff site. Then, they applied various e-field strengths that would be encountered in nature, like during stormy weather. The scientists observed spider behavior and measured the instance of tiptoeing and silk release in response to e-fields. Together, these scientists discovered that trichobothria respond to e-fields (Figure 4) and that e-fields encourage spider ballooning (Figure 5). These findings are not only cool, but they help us understand how species distribute and shape our earth.
So, don’t get caught up in a web of fear. Face spiders with curiosity and you might just learn something new!
