Females with penislike genitals and males with vaginalike organs are cases of a new extreme reversal of sex roles researchers have discovered in little-known cave insects.

These are the first examples of animals with genitalia that reverse the traditional sex roles, and the discovery could shed light on the conflict between the sexes in the animal kingdom, investigators said.

Scientists analyzed four species of insects from extremely dry caves in Brazil. All four species belong to the genus Neotrogla, just as dogs, wolves, coyotes and jackals belong to genus Canis. The first Neotrogla was discovered 18 years ago; adult Neotrogla range from about 2.7 to 3.7 millimeters (0.11 to 0.15 inches) long.