Oldest Known Cave-Dwellers Are 99-Million-Year-Old Cockroaches

Cockroaches—among the hardiest of insects—may be among the species guaranteed to outlive us all. But perhaps even more intriguing than the future of these persistent pests is their unusual past. A pair of 99-million-year-old roaches are now the oldest known animals that unambiguously adapted to life in caves, according to a study published this month in Gondwana Research.

The discovery earns the bugs the unique honor of being the only cave dwellers ever described from the Cretaceous, the period spanning 66 to 145 million years ago and the final era of the non-avian dinosaurs.

Preserved in lumps of amber from the Hukawng Valley in Myanmar, the two newly described species, Mulleriblattina bowangi and Crenocticola svadba, both belong to the Nocticolidae family, a lineage whose members still scuttle around Earth’s caves today, according Nature News.

Boasting a pale body, stunted eyes and wings, and legs that lacked protective spines, Mulleriblattina was “clearly a cave inhabitant,” study author Peter Vršanský, a zoologist at the Slovak Academy of Sciences, tells Michael Marshall at New Scientist. The roach, he explains, presumably stopped investing in certain traits that were no longer useful in the cramped, dimly lit cave environment. In their place, however, the insect appears to have sprouted some especially elongated antennae, perhaps to funnel its powers of navigation to the sense of touch.

Crenocticola has features that are somewhat less extreme, and may have been less tied to a cave-exclusive lifestyle. In fact, both species may have had reason to occasionally venture close to the cave entrance, where they became vulnerable to getting trapped in amber, which comes from tree sap.

These dark-dwelling insects almost certainly shared their caves with other animals, reports James Urquhart for Cosmos. But their remains have proved more elusive, due in part to poor preservation. And of the Cretaceous fossils that exist, few have features as unambiguously cave-adapted as the cockroaches, making it tough for researchers to definitively pinpoint their habitats.

Though more evidence is needed, Vršanský tentatively proposes that the two new cockroaches may have been among the few creatures that survived the mass extinction event that wiped out three-quarters of all plant and animal species 66 million years ago, according to Cosmos. That doesn’t guarantee, though, that these species—or even their direct descendants—are still around today. Most, if not all, of today’s cave-dwellers have evolutionary roots that post-date the demise of the dinosaurs.

But at least some members of the Nocticolidae family—a group that originated about 127 million years ago—clearly stuck around, and may have entered caves on several separate occasions.

Once that happens, Vršanský tells New Scientist, “evolution becomes very rapid and very strange … bizarre and strange forms originate.”

Katherine J. Wu | | READ MORE

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.