Surveying the oft-snubbed (and very cool) spider with citizen scientists
It's Saturday morning in early May at the Bluff Lake Nature Center, a modest suburban oasis in northeast Denver. An eager posse of spider hunters clusters around its intrepid leader, Paula Cushing, a petite woman with a dark braid, deep-set eyes and a fearless affection for eight-legged creatures.
"Without spiders, we'd be up to our eyeballs in insects," says Cushing, curator of invertebrate zoology at the Denver Museum of Nature and Science and director of the Colorado Spider Survey, a citizen science project aimed at chronicling the state's spider distribution and diversity. As top invertebrate predators with myriad foraging strategies, spiders play an important role in controlling insects, including common crop pests like wheat aphids. Some spiders act as pollinators; others provide key food sources for birds and reptiles. And yet spiders are some of the least-documented and most-misunderstood animals on earth.
The Colorado Spider Survey aims to provide baseline data to help scientists assess how resource development, urbanization and climate change may be affecting Colorado's spiders. Cushing conducts the survey through a series of public workshops and classes "to help nonscientists understand the scientific process and get them involved in a local research project." She teaches her students how to collect spiders in the field and how to identify the animals using features such as web shape, eye pattern and behavior. Since the survey's inception in 1999, she's trained more than 700 volunteers, who have sent her roughly 30,000 specimens from around the state.
Out at Bluff Lake, Cushing offers some hunting tips. "Think of (spider) habitat as three-dimensional," she says. "You've got the ground layer, you've got the bush, you've got the shrubs and the trees, and there are spiders living in all those layers." Meanwhile, Cushing's research assistant prepares the nets and collecting sheets the students will use to wrest spiders from the verdure.
"If you see rocks or logs, go ahead and move them and see what's underneath," Cushing says. "But don't put your fingertips all the way under; that's when you might get bitten by a black widow or centipede or scorpion."
The students, who include an environmental consultant and the manager of a cupcake shop, exchange nervous glances. Cushing smiles. Then, with the gusto and purpose of a general ordering soldiers into battle, she sends the hunters into the undergrowth. "Go to it, the trail's that-a-way. And enjoy yourself!"
On a path near the park's creek, Rebekah Thompson and Danielle Forte gleefully sweep canvas nets through budding willow thickets. For her master's project, Forte, a graduate student in museum studies at the University of Colorado, is developing a mobile phone application that will help people identify the spiders in their homes. "The more people know about spiders and their benefits," she says, the more likely they will "strip away some of the negative associations they might have" with the animals.
After about six strokes, the two women turn their nets inside out, shake the contents onto a white "beat sheet" and poke through the leafy dross. The disturbance prompts a rush of life: squirming inchworms, metallic beetles, clear-winged moths and, of course, a host of spiders, including crab spiders, jumping spiders and a single, spindly-legged long-jawed orb weaver.
"Oh! Shut … up!" Thompson says when Forte shows her the orb weaver. "That is so cool … look at the patterning." In the sunlight, the spider's pill-shaped body is a shimmering swirl of cream and gold. Forte gently scoops up the delicate creature and transfers it into a vial of alcohol. "It will be in spider heaven soon enough," she says with a sigh.
Meanwhile, Cushing makes the rounds: checking the students' progress, cooing over their finds, and inspecting vialed specimens with her trusty field glass. Around noon, she gathers her troops atop the bluff and breaks down the day's haul: "Cribellate spiders that build webs at the tips of vegetation, wolf spiders, Philodromid crab spiders," she says. "Roger collected Dysderidae -- the red louse hunters" -- all told, about 50 spiders from seven to 10 families. "It doesn't take a lot of collecting effort to get a huge amount of diversity," Cushing says. Indeed, arachnologists estimate that a single acre of grassland could be home to more than 2 million spiders.
Cushing's survey has already filled in some gaps in the scientific understanding of Colorado's spider communities. So far, Cushing and her crew have documented more than 650 spider species from 41 different families, recorded the existence of a handful of spiders not previously known from the region, and collected two species of triangle web spider that, in Colorado, seem limited to coniferous forests. What's more, Cushing estimates that five to 10 of the survey-collected species are completely new to science.
One of Cushing's goals is to use this kind of information to publish descriptions of Colorado's spider species. She also plans to use contemporary specimens and historical records to map species distributions, and analyze baseline data to determine if, in the last decade, there have been any significant shifts in the ranges or habitats of Colorado's spiders.
Back at the Museum, the students crowd into the arachnology lab and pull creature-filled vials from their pockets and backpacks. Cushing instructs the class to label each vial, specifying when and where the specimens were collected; without that information, she says, "the spiders will have died in vain." Survey volunteers will eventually catalogue the animals and add them to the Museum's growing arachnology collection.
Later, Cushing uses tweezers to remove the dripping corpse of a woodlouse hunter from a student's vial and place it under her microscope. The magnified image, like a frame from a monster movie, appears on the monitor at the front of the room. The students exclaim aloud at the animal's brick-red carapace, menacing fangs and primitive mien. This naked enthusiasm for a group of creatures so often maligned by the public is what drives the Colorado Spider Survey, a project that Cushing says "helps people understand that they too can be scientists at some level -- if they just have curiosity about the world around them."