Under a lateral lighting setup, the female (left) and male (right) of the Stygoparnus comalensis, sometimes known as the Comal Springs dryopid beetle, can be differentiated. In the female, the upper arrow points to a visible faint sclerotization of sternite 8 and the lower arrow points to the fused gonocoxites. In the male, the arrow points to sternite 8. (Images originally published in Kosnicky 2019, Journal of Insect Science)