Tibia

In several species of Leptometopa, the hind tibia is greatly enlarged and flat in males, and has a slight dorsal ridge in females. This means that either (1) these characters may be apomorphic for Leptometopa, and have been reduced in the L. niveipennis-group which has normal hind tibiae, or (2) they may have evolved within the genus, or (3) the genus is not monophyletic. Convergently with Leptometopa, an enlarged hind tibia has evolved in males of Desmometopa leptometopoides.
In Madiza there is a narrow longitudinal tibial organ at the middle of the posterior side of the hind tibia of males and females. It consists of a long and narrow depression, densely covered with short hairs. In addition to the tibial organ, males of Madiza glabra have abdominal glands which probably produce pheromones. It would be interesting to know with which behaviour the tibial organ and the abdominal glands are connected.
Tibial organs on the hind legs of males and females are an apomorphy for the Chloropidae. They resemble the organs of Madiza in structure, and are supposed to be either sensory areas or secretory in function (Sabrosky 1987b). Tibial organs may either be a synapomorphy for the Milichiidae+Chloropidae, and were then reduced several times within the Milichiidae and within the Chloropidae, or they may have evolved convergently in the Chloropidae and in Madiza. I prefer the latter hypothesis, because it is more parsimonious (ex Brake 2000).