Under a lateral lighting setup, the female (left) and male (right) of the Heterelmis comalensis, sometimes known as the Comal Springs riffle beetle, can be differentiated. In the female, the upper arrow points to the anterior strut of sternite 8 and lower arrow points to sternite 8. In the male, the arrow points to sternite 8. (Images originally published in Kosnicky 2019, Journal of Insect Science)