Two cockroach species that lived during the age of the dinosaurs are the earliest known animals to have been adapted for life in caves.

Specimens of the 99-million-year-old roaches are exquisitely preserved in amber from mines in Myanmar. Peter Vršanský at the Slovak Academy of Sciences in Bratislava and his colleagues named the species Mulleriblattina bowangi and Crenocticola svadba. Mulleriblattina has many of the typical features of its modern cave-dwelling relatives, such as small eyes and body size; Crenocticola might have been less specialized for cave life.

The new species are the only cave animals known from the Cretaceous Period, which lasted from 145 to 66 million years ago. The find suggests that many modern cave-living cockroaches in the family Nocticolidae, to which the new species belong, could have origins dating back 100 million years or more.

The authors say that some Cretaceous cave-living cockroaches might have fed on the guano of pterosaurs and dinosaurs, much as some cockroaches feed on the waste of birds and bats today. Cave-dwelling dinosaurs and pterosaurs might even have spread the insects from cave to cave.