We delight in Bacher sharing our passion for the disarmingly simple, yet significant question: ‘How many species are there?’ By applying our mechanistic model [2] to two hugely diverse, yet surely poorly known, insect taxa, he saves us the task. His result mirrors some selected plant taxa [2] and geographical regions [3] where there is only weak evidence for a decline in the numbers of species described per taxonomist.

Bacher suggests that: ‘We still need to describe species at a much faster rate than we currently do; we still need more taxonomists.’ We agree. The issue is where should that effort be concentrated and how can efficiency be increased?

Describing every species is the noble goal of efforts such as the Tree of Life (http://tolweb.org/tree/), Census for Marine Life (http://www.coml.org/) and All Taxa Biodiversity Initiative (http://www.dlia.org/atbi/). Given the many species missing from the taxonomic record, achieving this goal will probably take decades. In the meantime, there is an urgent need for taxonomy that matters. Current extinction rates [4] mean that there are species today that will never be discovered. As with flowering plants, missing species generally are likely to be in currently recognized biodiversity hotspots, which are places under extreme threat, and where local taxonomic capacity is limited. Missing species are usually rare: surprisingly large fractions of even well-known taxa with small ranges are recent discoveries [5]. Focusing taxonomic effort in these areas would be prudent.

Embracing new technologies could make a huge difference to knowing where species live, which is important in itself and vital to understanding the geographical variation of species. Citizen scientists, using clever technologies such as smartphone applications, can rapidly accumulate data that could quickly rival museum databases in the quantity of georeferenced material.

For example, iNaturalist (http://www.inaturalist.org) is an online initiative where users post pictures of species and interact with expert taxonomists to resolve species identification. One of the projects of iNaturalist, the Global Amphibian BioBlitz, quickly harnessed these citizen scientists to collect georeferenced picture specimens of approximately 90% of the amphibian families of the world (11% of species) in just a few months. Some yet-to-be-identified specimens are probably ones that are new to science.