Carnivorous Nights_ On the Trail of the Tasmanian Tiger - Margaret Mittelbach [99]
“We've got one species of glowworm in Tassie—they're endemic. They only live in wet caves or terrestrial wet environments—and they're just above us here.” The species was Arachnocampa tasmaniensis, which means Tasmanian spider grub.
Although not related to spiders any more than they were related to worms, A. tasmaniensis had a spider's ability to make sticky silk strands. “They suspend themselves from the undersurface of the cave's ceiling by threads, and it's like they're in a little sleeping bag”—a hollow tube made of silk and mucus—“and from there they drop down multiple threads of silk—very sticky, mucousy fishing lines to catch their prey. That nice dark blue glow—it's them burning their waste products, but it also attracts prey. The brighter the glow, the hungrier they are.”
The glowworms' prey is flying insects. The larvae of mayflies, stoneflies, and caddisflies are aquatic and sometimes get swept from terrestrial rivers into underground streams. When these insects emerge from their larval stage and turn into flying adults, they find themselves stuck in the dark. Then, when they see the glowworms' lights, they head right up— and get caught in the sticky fishing lines. The glowworms simply reel them on up.
The glowworms themselves stay in their larval incarnation for up to eighteen months. When they finally turn into flying adults, they have only three or four days left to live. “They don't eat—they don't even have mouthparts. All they do is go out and reproduce,” Brooke said. “And they do it carefully, because every one of those glowworms has thirty to fifty threads of silk. And often they get caught in their own fishing lines.”
With each passing second—as our pupils dilated—more and more glowworms became visible. There was something creepy about the illusion—these grubs and their sticky little threads so effectively posing as a starry night. The lights were beautiful, intoxicating, and we wondered if people ever became mesmerized by the glowworms—thinking they were sleeping under a starry sky, falling into a cave dream, and never waking up.
Certainly, some animals came in and never came out. “As you can hear, we've got a stream going underneath. That brings other cave fauna in, accidentals,” said Brooke. “Often in floods, we get platypus and trout that have been pushed through from about a thousand meters up, from the Great Western Tiers. It's very rare, but they end up down here. And we also get wallabies and wombats that fall through sinkholes. They die. They fall into the water and eventually they decompose—and encourage more insect life in the cave.”
After the wind pushed us out the cave door and back into the world of the living, Brooke decided she wanted to show us something else— a wilder cave in a different part of the karst system. As we drove on a narrow, winding road through more wet eucalypt forest, Brooke told us a little more about herself. She was a teacher during the school year—she educated autistic children—and worked as a ranger with the Parks and Wildlife Service during the summer. She lived in a small commune called Platypus Bend. They didn't have electricity and grew their own food. She preferred to live off the grid.
On the drive over, Brooke saw a dead animal in the middle of the road. It was a young devil—badly mashed.
“It's sad, you know. I saw him last night.” Her face creased with concern.
“You recognize it?”
“Yeah, you just get a feel for them, their size and markings.”
Brooke stopped to move it to the side, and Alexis jumped out, too. The animal's entrails were splayed out across the blacktop, and its nearly liquefied carcass was crawling with flies. Alexis pushed his camera right up next to the body. “Could I get you to pose with that?” he asked. Brooke didn't seem to hear him, but he was able to snap her picture as she used a plastic shopping bag for a glove and moved the body into the brush.
Then we got