A total collection database for the Australian Sciapodinae (Diptera: Dolichopodidae) , comprising 259 species, 1 109 sites and 2 452 collection events, was analysed to determine how collections accumulate species, and how this affects concepts of richness , and rarity. The year of first collection is seen as a more accurate indicator of species accumulation than year of description. Changing collecting methods and number of new sites sampled have a marked effect on the number of additional species accumulated. About half of all species can be considered rare , being known from 1–3 collecting sites. Many rare species were discovered only as a result of continuous or repeated trapping at a single site. Allowing for habitat differences, site richness is proportional to collecting intensity over time, and it is difficult to distinguish collecting history fro many inherent or special site richness. Such patterns are regarded as representative of small, species-rich flying insects, especially Diptera and Hymenoptera.