Some millipede species will practice a form of mate guarding. The male remains with the female, riding on her back until her eggs have been laid. To avoid dislodgment, male millipedes must cling to the smooth surface of the female. Chung and Moon prepared scanning electron micrograph images of male and female millipedes. Their image (left, arrow) reveals dense bristles extending from the ventral side of the male millipede tarsus forming an adhesive pad. The tarsal pads are present on the male, that must cling, but not on the female that has no need to cling.
*Kyung-Hwun CHUNG and Myung-Jin MOON. Microstructure of the adhesive pad in the millipede Orthomorphella pekuensis. Entomological Research 38 (2008) 216–220