The itsy bitsy jumping spider, part 1

Shahar Madjar, MD

My interest in the jumping spider stems only from my wish to find the source of my own heart’s rhythm, and yet, I can’t ignore the little spider’s charisma, its charm, its romantic nature. It is small–about the size of a pencil eraser–and hairy. It wears its crunchy skeleton on the outside, like the armor of a medieval knight. It has eight legs and it walks slowly, but it jumps with the agility of an Olympic athlete. To attract its female counterpart, the male-spider will display its hairs, show its more colorful parts, dance in a zig-zag, vibrational movement and make buzz and drum-rolls sounds. Who could resist such a song-and-dance show of affection?

Long before I became interested in it, the jumping spider abandoned net-knitting. It has no time for elaborate net construction and no patience to sit idle and wait for its prey to be caught in its net. Instead, it actively hunts its prey by jumping at it. First, it needs to identify its prey. Like a cat, it stealthily stalks and pounces on its prey. It does so using its eight eyes which allow for an almost 360-degree panoramic, sharp view of the environment.

In a laboratory at Cornell University, scientists working with Professor Ronald R. Hoy were able to gently introduce a miniature, hair-sized electrode into the brain of several jumping spiders. They measured the electrical activity in the spiders’ brains in response to images projected on a screen in front of them: images of a fly (a prey), and of other jumping spiders (potential mating partners or competitors). The researchers then repeated the experiments while covering different sets of the spiders’ eyes. The results were astonishing: put an image of a fly in front of a jumping spider and its brain would fire as vividly as a seismograph during an earthquake; cover even one set of eyes and the electrical activity in the spider’s brain would die down. The jumping spider doesn’t just see its prey, it is able to integrate and compute stimuli from four different pairs of eyes into one coherent message: ‘This is my prey!’ Or, ‘This is my mate! Whatever it is, I re-cognize it!’ The spider must possess at least some form of cognition.

In a different set of experiments the same group of researchers were able to prove, two years later, that the jumping spider cannot only see and recognize its prey, it can also hear at a distance of up to 3 meters. The spider’s brain, mind you, is no bigger than a poppy seed.

If the jumping spider doesn’t fill your heart with awe (do you belong to AA–arachnophobe anonymous?), perhaps you would be more impressed by the mystery of the Monarch butterfly migration. The Monarch is a lovely creature whose body is light and beautifully painted in yellow-orange to match the sunshine, whose wings are as thin and semi-translucent as onion skin–an embodiment of air and light. Every autumn, millions of Monarch butterflies migrate from the ominous freezing territories of North America to Mexico and Florida. Scientists claim that the Monarchs orient themselves by using a highly-specialized circadian clock integrated with a sun-compass located in their antenna. There are several theories attempting to explain the Monarch’s ability to migrate with elegance and precision, and no theory is accepted by all–a sign that the jury is still out. With a brain made of a few cells, the Monarch can find its way–a distance of 3,000 miles–better than I can find my way to the post office in a neighboring town, even with my GPS turned on.

How can the jumping spider, whose brain is no bigger than a poppy seed, perceive and analyze signals of light and sound? How can it detect its small, moving prey, compute the distance to its prey, calculate the forces it should use for jumping? And how can the Monarch butterfly, with a brain even smaller, find its course? I wonder: what is the driving force behind the spider’s behaviors–the drive to hunt, and to mate? Does it feel hunger? Is it romantic? Perhaps even self-aware? And what force is it that compels the Monarch butterfly to seek new territories?

The beat of my heart; the jump of a spider; the migration of a butterfly: where are all these drawing their signal from? Could a 17th century philosopher–a believer in the oneness of the universe–solve the mystery better than contemporary scientists? I shall return.

Editor’s note: Dr. Shahar Madjar is a urologist at Aspirus and the author of “Is Life Too Long? Essays about Life, Death and Other Trivial Matters.” Contact him at