“In order to catch a fly, you must be quicker than the fly.”

That was a quote from a kung-fu movie my brothers and I were watching one day many years ago. I forgot the title of the movie, but I remember this line clearly because my brothers and I laughed when we heard it. It was from one of those old kung-fu masters teaching his student, and it just sounded a bit too simplistic, obvious, and unoriginal.
Oh, really, do we really need to be quicker? Well, duh, of course we do. Remember when Mr. Miyagi was showing Daniel in the movie The Karate Kid how to catch a fly with chopsticks? Well it doesn’t take a rocket scientist or wise kung-fu master to see we need to be quicker than the ultra-quick fly in order to catch it! Or does it?
Ever notice how difficult it is to catch a typical housefly? Even with a fly swatter, the fly can sense your movement from a few feet away. Why is that? The fly is built for reflexive movement. It has numerous parts to its large compound eyes. Similarly, when an object is thrown at the human eye it blinks instantly without thinking. It is reflexive, much like the fly. That is why when you swing your hand or swatter at a fly while it is motionless and seems not to notice you, it just flies away in a blink of an eye, literally.
So how does a mantis catch a housefly then? When we first thought of feeding one of our pet mantids with some of the flies flying around in the house in the summer time, I thought there is no way in the world the praying mantis will catch one of them, even in a small cage. I thought even with its snap of its spiky forelegs, which is a blur at 1/20 of a second, the praying mantis’ initial approach will be detected by the fly before it can get close enough.
Closing the Distance; the Swaying Leaf Technique (I just made that up!)
Well, little did I know that years of natural evolution has equipped the praying mantis with a gift I had yet to witness at the time. I call it the ‘swaying leaf’ technique. Ever noticed how leaves, twigs, or reeds sway so gracefully when the wind blows? Well, I theorized that insects, including flies, have come to live with this movement for millions of years and gave come so accustomed to it that they don’t react to it – it’s just a leaf, not a threat or predator.
Through years of observation, the mantid has learned to mimic the sway of the leaf, the movement of the wind, to close the gap between it and the prey. Once within striking distance, the snap of the mantis’ forelegs is employed more effectively to capture the prey. This is why a short punch or strike in boxing or martial arts is harder to detect and avoid and is usually more effective than a long winding swing from afar.
How the mantid learned this technique exactly, I guess I don’t know. It is part of the wonder of nature’s evolution. And it works. I’ve first seen the mantis employ this swaying leaf technique and the housefly just stood there motionless, seemingly entranced, thinking the mantis was a leaf as it swayed from side to side while inching closer and closer, until the mantis was almost just one inch away and snap! Bye, bye fly.
Once I can get a video of that, I will post it.
So technically it is not the natural speed (only about 5 miles per hour) of the housefly that allows it to escape a moving threat, it is the reflexive instinct AND the ample distance of the threat that it senses that gives the fly enough time to escape. Once this distance is closed the predator or threat has the advantage, much like a tiger or cougar stalking it prey.
Now my brother, who is a master insect-catcher uses the same ‘swaying leaf’ technique with a jar to catch houseflies.
In order to catch a fly, you must be quicker than the fly.” Well maybe not necessarily quicker, just smarter!
By Noy Ilao