Tumulus (biology)

For other uses, see Tumulus (disambiguation).

In biology, a tumulus (pl.: tumuli) is a small mound of earth surrounding the entrance of the nest of fossorial (ground-nesting) ants, bees, or wasps. In the case of ants, this mound is almost universally referred to as an "anthill" (or "ant hill"); the worker ants typically pile sand or soil outside the entrance to the nest in the process of excavation.^[1] In the case of bees and wasps, there is no corresponding common term, and such mounds are referred to as "tumuli" (e.g.^[2][3]).

The poorly-defined tumulus of a nest of Andrena fulva, a mining bee

The tumulus is typically symmetrical or nearly so, a simple accumulation of excavated material, though there are occasional examples where the mound is skewed towards one side, with the entrance therefore not in the middle of the mound.^[2] If the material is loose, it may be blown away by wind or washed away by rain, but as nest excavation generally is continuous over the course of a season, the tumulus is usually re-formed fairly rapidly.^[3]