The Science of Fear: Hymenoepimecis argraphaga’s Chemical Manipulation of Behavior in Orb-Weaver Spiders and Homo sapiens
When people say they work with flies, you say, “yeah, OK,” remembering counting the fruit flies in genetics class, clasping their wings with tweezers and setting aside the percentage with eyes like bright vermillion pincushions instead of basic insect brown. The way they start to twitch and squirm as the CO2 gas you used to knock them unconscious starts to wear off and you have to hurry to put them back in a glass tube labeled “Group A – Drosophila.” Or maybe they mention C. elegans, those beautiful, dancing strands, glowing ghostly as ectoplasm under the microscope. If people say they work with these worms, it’s normal—it’s understandable. Despite their supernatural appearance, their genome and nervous systems are mapped out, and even their cell lineage is completely known, every division in their short 2-3 week life accounted for. Or the model organism D. rerio, zebrafish, developing under the microscope with optically clear skin, revealing every organ, vessel, and nerve. Amazingly regenerating damaged tissue, organs, spinal cord and eyes, yet sharing 70% of their DNA with humans, these are creatures to which we aspire, not from which we cower. In science, people work with cell-thin slices of mouse brains, X. laevis frog embryos, and all kinds of things other people might think are scary and gross. There are fly guys, worm guys, fish guys, mice guys, frog guys, and even yeast guys. No big deal. These creepy-crawlies are controlled. They are scientific, after all. Nothing to be afraid of.
But spiders are another story. Something about their spindly legs is spellbinding, simply artistic, as they hide squatting in the corner, now running across the wall. No, not hide. Not run. They are above such prey-like behavior. Instead they are stately, unconcerned—gliding, racing with the wind, and oozing benign beneficence. I had always been fascinated by spiders and their parallel, small existence in the corners of our rooms ever since I had read “Charlotte’s Web” at an impressionable, young age. After that, I had taken the author’s point to heart and never quite understood how someone could be afraid of spiders.
That’s why, when one day I grew curious about what type of scientific research, if any, in which spiders were involved, I was horrified to learn spiders were not immune to the struggle of the animal world, the brutal touch of the Nature Channel clouding the pattern of their beautiful webs, their wisdom, and the quiet sense of self I had always attributed to them. I had even imagined them a type of peer, for as I delicately manipulated the fruit flies on one side of the room, they’d be adroitly catching a housefly in another, their tiny tines riffing with surgical clarity. Knitting, painting, writing. But now I find out that they are the victims, the ones being manipulated, in a horror story akin to Dracula—mind-control, blood-sucking and all—a story rooted in some of our own deepest psychological fears. Yes, when even spiders are preyed upon, spiders are not what you should be afraid of.
I’m talking about Hymenoepimecis argyraphaga, a species of small, parasitic ichneumonid wasp native to Costa Rica that uses a host spider, Plesiometa argyra, in its reproductive cycle. I had foolishly not realized that parasites came so small or that they plagued animals other than mammals, but here they were. During this process, the parasitic adult female wasp lays its egg on a orb-weaving spider, and the larva grows by sucking the spider’s fluids.
Then, when the wasp larva is ready to pupate, it injects the spider with a chemical that affects the spider’s behavior. The spider starts weaving a different web, composed of a small step in normal weaving that is repeated over and over to create thicker and stronger radial lines.
If the larva is removed during this stage, the spider continues its aberrant web-weaving for several days before eventually returning to normal behavior.
If left, the larva kills the spider, sucks the host dry, and discards the husk of a body. Then it builds a cocoon in the center of the spider’s web. The modified web helps support the weight of the cocoon as the larva pupates and emerges to mate and start the parasitic process over.
This sounds like something from a bad horror movie, one with radioactive, 50-foot ants and swarms of bats, but it is completely real. After learning this, you may have trouble falling asleep or have nightmares, your eyes widening and pulse quickening deep in the dark of night. You may hesitate and try to steady a trembling hand before killing that spider in the bathtub. The proximity. It may be infectious. It could happen to you. You may even try to warn everyone you know, your voice tense and high, alighting to the ceiling and bouncing about like a broken wing. I know, I’ve been there, studying the phenomenon first-hand as the vague unease followed me about and threatened to break my heart out of the cavern of my chest, a caged thing, a monster. The rote work with flies, worms, frogs, all-consuming but seeming less and less important. Maybe scarier, maybe more banal, maybe useless, all at once. Science seeming as implausible as anything else. My mind and body giving out, tiring, weak with dread, and me not caring anymore.
But, eventually, the erratic and irrational behavior will stop and you will return to a normal daily routine. Because, really, by then you’ll either be safe or completely drained dry, and either way it will simply cease to matter.
