An Asian Weaver ant carrying 100 times its body weight while upside down — Thomas Endlein, via the BBSRC.
The Journal of Comparative Physiology A once published a cover story on “passive control of pretarsal attachment in ants.”
Translated into English that you and I can understand: certain ants have incredibly sticky pads on their feet that let them walk upside down. A fundamental question facing researchers though is that given the adhesion, how do they walk without getting stuck?
How to Shoot an Ant
Congratulations are in order as Endlein just won the BBSRC Science Photography competition for the amazing image above. He explains how he took it:
“The image was taken using a Canon EOS 5D with a 2.8/100 mm macro lens and twin flash guns. To get the shot I made use of their natural behaviour: these ants are very aggressive towards almost anything which comes close to them. They try to grab and bite to take down potential threats, like other insects. And once they grab an object they won’t let go for a very long time. So they did with the little weight suspended on a string.” — Dr. Thomas Endlein
“The basic principle of sticking is to use a thin fluid layer in-between the adhesive pads and the substrate,” explains Dr. Thomas Endlein of the Centre for Cell Engineering at Glasgow University. His research demonstrates that the Asian Weaver ant can control its adhesive strength on three hierarchical levels: the foot, the leg and the entire body.
“On the ‘foot level’,” he says, “they can change the size and shape of their pad dynamically to adapt the contact area according to the experienced load. If they have to carry heavy loads they increase the contact area, when they need to run they decrease it.”
Such is shown in the image above where we see an Asian Weaver ant carrying 100 times its body weight while upside down. If I do an apples and robots comparison that could be me carrying 18,000 extra pounds on my back. Additional adhesion from my legs and body would help me do it.
“Ants vary the number of their feet in contact,” says Endlein as he outlines how ants demonstrate body control. “When they run upside down they often keep at least 4 feet in contact, whilst running upright they use only three feet simultaneously in contact.”
And then the sticky business about not getting stuck. The metaphor Endlein uses is tape attached to a surface. We’re generally successful removing it when we pull it off at steep angles. Shallow angles? Not so much.
“Ants use the same mechanism,” he says. “In case they want to stick they keep their legs in a shallow angle towards the surface, when they want to release them, they increase this angle and peel off easily.”
Understanding the biology of the Asian Weaver could help scientists develop better glues and adhesives. If so it wouldn’t be the first time the powerlifter demonstrated its worth to humans. The fiercely territorial ant has defended Southeast Asian citrus orchards from invading insect pests for the past 1,500 years.
