Sometimes many urchins collect together in one locality in dense aggregations.

If so, these species are most likely to form dense aggregations that would reduce diversity in local areas.

This gastropod is generally found in dense aggregations up to 1,000 m.

Among the social insects dense aggregations occur but without the loss of complex social organisation.

Slimehead behaviour is not well studied, but some species sporadically form dense aggregations.

Prolonged breeders do not form such dense aggregations.

These are dense aggregations of very old stars that orbit the Milky Way, but are separate from it.

Individual fossils are common throughout the Burgess shale, where they often occur in dense aggregations.

Some species form dense aggregations, either on the sea floor or in the water column, and a small number are subject to commercial fishery.

As well as these pelagic swarms, many species form dense aggregations on the sea floor.