New species of assassin bug found sniping in cave
The labyrinth bug, named for its cave habitat (and not the David Bowie movie), was formally described last week in the journal Zootaxa. These spindly killers use their spiny front legs to seize small insects and other prey, and then pierce their catch with a sword-like snout in order to suck up its juices.
The new species (Phasmatocoris labyrinthicus), part of the assassin bug family Reduviidae, was discovered in Kartchner Caverns State Park in Cochise County, Ariz. It was first noted during a survey in 1990, but was not studied in-depth until a two-year invertebrate survey in 2009-2011 conducted by the Arizona State Parks.
Robert Pape, a research associate with the University of Arizona in Tucson, conducted several searches of the cave in order to describe the species and document its behavior and natural history.
The bug proved elusive. For the first 11 months, Pape could find only corpses.
Then, on Aug. 10, 2010, Pape noticed two dead wasps and a dead ant lying on the floor of the cave. Looking up, he scanned the cave walls. In a small fissure tucked below a mound of soil built by termites lay his quarry, ready to ambush.
To test the labyrinth bug’s palate, Pape guided a spider toward an adult female and watched as she stepped back, grabbed the spider and impaled it with her snout.
Pape noticed some other aspects of the bug’s body design that make it well-suited for specializing on spiders, such as a brush-like set of hairs on its front legs that may be used to manipulate spider silk. The brush is the longest ever recorded in the genus Phasmatocoris.
While in the cave, Pape also observed an adult labyrinth bug playing with the remains of an old spider web, wrapping the silk strands around its legs and creating tension that could be used to trap spiders or to signal the arrival of a potential meal.
More field observations are needed to explicitly test these ideas.
“We’ve only seen this animal maybe eight to 10 times ever,” Pape said.
One of the most surprising aspects of the new species is that it lives far away from its closest relatives; all but one of the other bugs in the genus Phasmatocoris are found in the New World tropics, where they live in rain forests and other non-cave habitats. How it got separated from the pack is a biogeographic puzzle that needs sorting out.
However, there are some clues that the labyrinth bug may not have always lurked in the underworld.
At the end of the last ice age 11,000 years ago, the climate in Arizona was much wetter and cooler, a far cry from the semi-desert that exists there today. The bug’s lack of any obvious cave adaptations (such as blindness or lack of pigment) and its preference for more humid parts of the cave suggest that it may have once roamed the outside world before retreating into the cave.
“I think they were probably living in rock shelters and cave entrances,” Pape said.
The bug’s discovery underscores the importance of basic field surveys to document biodiversity. Sixteen other new species, including a stay-at-home millipede (it is confined to a 20-foot area of the cave), a scorpion and several beetles were also found as part of the Arizona State Parks survey.
“And I’m sure there are things there that we haven’t found yet,” Pape said.
Caves are hotspots for finding new species and are attracting increasing attention from taxonomists and evolutionary biologists.
Joel Ledford, a research associate at the California Academy of Sciences, earned his doctorate by studying a group of blind cave-dwelling spiders in the genus Tayshaneta. He spent lots of time between a rock and a hard place looking for organisms.
“There’s a lot of mystery there — caves are usually remote and difficult to access, and so there’s a pretty high likelihood of seeing things that nobody has ever seen before,” Ledford said. “There is no light. There are no plants. Everything is a predator. It’s sort of like a secret little world.”
You can read a summary of the study here.
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