As a sleepy tree frog awoke in the coming dusk of a muggy September evening, its bulbous eyes would have noticed something odd about its usual view from the fieldstone wall at the entrance to Picnic Point. An alien invasion of more than 30 bobbing lights bore down swiftly upon its stone cubby, giving it no choice but to retract back into its daytime guise of being a particularly rotund clump of lichen. To the frog’s relief, the lights mostly sailed right by in the hands of arachnid enthusiasts making a bee-line for the webs strung upon the stone wall’s gates. Puffs of corn starch mist illuminated by eager beams lit up a tapestry of silk between the dark cast-iron bars.
Harvestmen (daddy longlegs) researcher Guilherme Gainett led us on a captivating night-time hike with help from spider researcher Siddharth Kulkarni. The two Sharma Lab experts wove their own web of arachnid facts and stories around the countless eight-legged critters we were finding. Harvestmen and spiders, while they look similar, are two distinct varieties of arachnid. Contrary to popular myth, harvestmen are not venomous like their spider relatives. They also have only one discernible body segment (see picture below). Spiders, in contrast, have a distinct thorax separated from their abdomen by a narrow, flexible waist called a pedicel. Additionally, harvestmen lack the ability to make silk and cannot make webs like their spider cousins.
Orb webs, sheet webs, funnel webs, and other ingenious works of architecture took form before our eyes between leaves and branches. These different web forms tell stories not just of different ways of life, but also different spider evolutionary histories. Some spiders wait for prey to trap themselves, while others actively cast their nets upon prey, or "fish" by swinging long sticky lines. Did you know the organ spiders use to create their silk is called a spinneret? The spinneret is composed of many microscopic "spigots" that each produce a single thread that is woven together into the strands we can see with our naked eyes.
The sparkling jewels of spider eyes glittered from the ground too, as wandering spiders hunted through the leaf litter in the hundreds. We learned that just as cats and dogs have a reflective “tapetum lucidum” layer in their eyes that helps with night vision, so do many spiders! Appreciating this glimpse of the multitudes of arachnids one can find in the Preserve deepened my sense for what little we still know about the eight-legged creatures that live with and around us in Madison. Siddharth told us that for every species of arachnid known to science, there may be another yet to be described.
Stay tuned about further arachnid-themed events in the future as we work with Guilherme and Siddharth to continue to learn about all the eight-legged creatures that call the Preserve home.
Report by Will Vuyk. Photos provided by Eve Emswhiller, Guilherme Gainett, and Will Vuyk.