Mulga Ant (Polyrhachis macropa) (4/5)

Hymenoptera: Formicidae

Polyrhachis macropa  

The raised entrances of the Mulga Ant nests are "thatched" with Mulga needles.

The raised rim would help prevent rainwater from flooding the nest but I'm not sure what the purpose of the thatch is. Perhaps they make the nest more visible to large animals so less likely to damage, impede the ingress of foes, or help prevent erosion by wind or rain. Anybody else have any ideas? A significant amount of work obviously goes into the task.