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In biology, a tumulus (: tumuli) is a small 
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. 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.
mound
A mound is a wikt:heaped, heaped pile of soil, earth, gravel, sand, rock (geology), rocks, or debris. Most commonly, mounds are earthen formations such as hills and mountains, particularly if they appear artificial. A mound may be any rounded ...
of earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
surrounding the entrance of the nest of fossorial
A fossorial animal () is one that is adapted to digging and which lives primarily (but not solely) underground. Examples of fossorial vertebrates are Mole (animal), moles, badgers, naked mole-rats, meerkats, armadillos, wombats, and mole salamand ...
(ground-nesting) ant
Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Cre ...
s, bee
Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfamil ...
s, or wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...
s. 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. In the case of bees and wasps, there is no corresponding common term, and such mounds are referred to as "tumuli" (e.g.Danforth, B.N., Minckley, R.L., Neff, J.L. (2019) ''The Solitary Bees: Biology, Evolution, Conservation'' Princeton University Press, Princeton, NJ, USA. 472 pp.).
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. 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.
References
{{reflist Insect ecology Shelters built or used by animals