Cave-dwelling bugs in Brazil, belonging to the rare Neotrogla genus, set themselves apart in more ways than one, National Geographic reported.
Scientists studying the bugs found that the females possess genitalia structurally and functionally similar to a penis, while the males use a vagina-like opening to distribute their sperm. The researchers published their study in the journal Current Biology.
"It was a surprise for all of us," Rodrigo Ferreira, the study's co-author, said. "This elaborate female penis is completely unique."
It's also quite fit.
Researchers looking at the copulating insects found the couples mated for an average of 50 hours, with one pairing hitting the 73-hour mark. The scientists said the findings could be used to test different hypotheses about sexual selection and the evolution of genitalia.