Females (unknown in Madecadryinus ranomafanensis and Madecadryinus silvanus)

1. Lateral suture of dorsal surface of mesosoma not present from propodeal spiracles to lateral corners of keel surrounding posterior inclined region ...Madecadryinus relictus Olmi

- Lateral suture of dorsal surface of mesosoma present from propodeal spiracles to lateral corners of keel surrounding posterior inclined region ...2

2. Eye very small; head more than eight × as long as eye ...Madecadryinus semicaecus Olmi

- Eye larger; head less than eight × as long as eye ...3

3. Antenna slender, with antennomere 6 longer than broad ...Madecadryinus humicolus Olmi

- Antenna thicker, with antennomere 6 about as long as broad ...4

4. Head and anterior surface of mesosoma dull, granulate ...Madecadryinus opacus Olmi

- Head and anterior surface of mesosoma shiny, finely punctate and unsculptured among punctures ...Madecadryinus politus Olmi

Males (unknown in Madecadryinus humicolus, opacus, politus and semicaecus)

1. Mesoscutum unsculptured or finely punctate and unsculptured among punctures; ocelli large ...Madecadryinus silvanus Olmi

- Mesoscutum granulate; ocelli small or large ...2

2. POL less than twice as long as OOL ...Madecadryinus relictus Olmi

- POL about 3 × as long as OOL ...Madecadryinus ranomafanensis Olmi, Copeland & van Noort