On 12 February 2014, a new species of beetle was identified. It had a head shaped like a hexagon, with a striking metallic green-blue-purple colour, and jagged antennae.

That may not sound startling: scientists describe about 50 new species every day. The Natural History Museum (NHM) in London, UK, which owns the specimen, identifies 400 per year.

But this was not just any old new beetle. It was collected by Charles Darwin himself, in Argentina in 1832, during his voyage on the Beagle. Yet despite its flashy appearance and historic origins, it was 180 years before Stylianos Chatzimanolis of the University of Tennessee at Chattanooga realised it was a new species. He named it Darwinilus sedarisi.

It's an extraordinary story, but it's one we will hear again and again. You might think we would know about most of the species on Earth by now, but in fact there are probably millions still to find.

There are as many as 7.5 million species awaiting discovery

So if you want to discover an organism that is new to science, where should you look? Are there certain types of lifeforms that are less well-known, and so make good targets for would-be new-species-baggers? And what exactly is the point of tracking down and naming previously undescribed animals, plants, fungi and other living things?

Right now there are 1.2 million or so known living species. Some 15,000-20,000 are added to the list every year. This may seem a lot but there are plenty more to find. In 2011, researchers estimated there are as many as 7.5 million species awaiting discovery.

When scientists think they have found a new species, they must first check that it has not already been described. That can mean visiting museum collections, speaking to other specialists, and studying its DNA. They must then choose a name and publish a detailed description, especially of characteristics that distinguish it from other species.

Out in the wild

When we hear that a new species has been found, the story often involves scientists in exotic locations. For example, in 2013 researchers were dropped by helicopter into a remote mountain range on Cape Melville in northern Queensland, Australia. They found several new species within days, including the leaf-tail gecko, a golden-coloured skink and a boulder-dwelling frog.

Go to a good museum and take a careful look at their specimens

Those who can make it out to remote rainforests, or collect samples from the deep ocean trenches, can pretty much guarantee to find new lifeforms.

Yet it's wrong to think that most discoveries are made instantly in the field. It does happen, but you may have a better chance, and certainly your travel costs will be lower, if you do what Chatzimanolis did: go to a good museum and take a careful look at their long-stored specimens.

"The great natural history museums themselves make up one of the last great frontiers of exploration," says Max Barclay of the NHM.

"I was really surprised because I thought the Darwin collection had been pretty well studied," says Chatzimanolis.

Don't be put off if the specimens you encounter in the museum have been gathering dust for decades. It was 182 years between Darwin collecting D. sedarisi and Chatzimanolis describing it as a new species. This is longer than normal, but not by as much as you might think.

In 2012, researchers from the National Museum of Natural History in Paris, France estimated how long it took before newly-collected specimens were described as species. They looked at 570 of the thousands of species described in 2007, and found that the average delay was 20.7 years.

It might take you three or four years to get them sorted out

Why does it take so long? Part of the answer lies through a large brown door leading off from the first floor balcony of the NHM's iconic main Hintze Hall. In a room 16m by 73m, 1,100 pale green cabinets, each with 22 drawers, are arranged in formation and stacked two high. They contain around 10 million beetles from 170,000 species.

Barclay, who manages the beetle collection, slides a large blue canvas shopping bag from beneath a table. He unzips it and pulls out a box containing a neat grid of about 400 beetles, each carefully labelled in tiny writing. There are dozens of other boxes in the bag, and dozens of similar containers piled on and under tables, or stacked on shelves around the room.

"If you come back from an expedition with 20,000 beetles, it might take you three or four years to get them sorted out and mounted," he says. Then they have to be sorted into the right family groups, and finally into species.

You may not fancy your chances of finding new species in a museum, with experts like Barclay and his team already on the case. In fact the competition is not as stiff as it might appear. The biggest bottleneck is finding specialists in each group, who can identify the species.

Roger Booth is visibly excited by a featherwing beetle

"There are 400,000 beetle species," says Barclay. "With so many you can't guarantee there is going to be an expert alive in every generation to cover all the different groups. We have four or five beetle specialists at the museum but we all have other responsibilities, so really we have the equivalent of one person working on the taxonomy of 400,000 beetles."

The species identification that Barclay and his team are able to find time for is carried out on the floor above the storage room. Here they wield their entomological forceps over cases of specimens, watched over silently by terracotta clay wild boars, owls and antelopes set into the building's roof pillars

In one of many cubicles, entomologist Roger Booth is visibly excited by a featherwing beetle he is examining. At 0.3mm in length it is barely visible to the naked eye. With the aide of a microscope it looks brown and, well, not all that exciting - to the uneducated eye at least.

If you don't fancy spending hours in dusty museum storage cupboards, there are other options. Sometimes, new lifeforms are discovered right under our noses.

Bryn Dentinger, Head of Mycology at the Royal Botanic Gardens, Kew, in London, for example, discovered three previously-undescribed species of Boletus fungi in a packet of dried porcini his wife bought in a shop.

The patch-nosed salamander was discovered some 20m from a country road in Georgia, US, in 2007, and the Atlantic Coast Leopard Frog was first identified the following year on Staten Island, New York.

If you do want to find a new species, it might be worth bearing in mind that some life forms have received much more attention than others. The 2011 study of undiscovered species concluded that, while about 14% of the 8.7 million living species had been described, the proportions already identified varied widely by kingdom. So while 70% of plants are known, that figure drops to 50% for algae, 22% for single-celled protozoa, 12% for animals and just 7% for fungi.

This is partly because we have tended to focus on species we can eat or otherwise use, and partly because some types of organisms are just easier to spot. For instance, many fungi are microscopic and live inside their food source, whether that is soil, wood or leaves. Even if you find them, the filaments of different species often look identical.

There is no hard-and-fast definition of a species

At this stage, you might be asking yourself "what's the point?" Do we really need names for all those millions of elusive undiscovered species? Is all this trekking through remote jungles and rummaging through museum storage cupboards actually worth the effort?

This question becomes even more pressing when you consider that there is no hard-and-fast definition of a species. In general, we say that two organisms belong to the same species if they have more characteristics in common with each other than they do with organisms of different species, and if they can breed to produce fertile offspring.

But sometimes different breeds of a species can vary enormously, as anyone who has looked at domestic dog breeds will know. Also hybrids, the offspring of two species, can sometimes be fertile. So deciding whether an organism is different enough to be a new species is inherently subjective.

Magic, er, fungi

The first thing to say is that those unknown species may well have amazing abilities that we would find useful. That is particularly true of all those unidentified fungi.

"Fungi are fundamental to our world," says Dentinger. "We rely on them heavily for foods and medicines, they are responsible for most decomposition of dead matter, and virtually all plants depend on fungi for water and nutrients. All these important roles come from just 1% of the 100,000 known fungi, so we can only imagine the potential we could derive from the species that are yet to be described."

But beyond that, some of the biggest breakthroughs in science could never have happened without a detailed understanding of the differences between species. For one thing, Barclay says, Darwin might never have discovered that species evolve by natural selection.

When the Beagle arrived at the islands of Madeira and the Canaries, Darwin saw beetles that couldn't fly. The theory of the day would suggest a benign creator had made them this way as otherwise they would have been blown out to sea. But Darwin thought otherwise.

Darwin was focusing on very fiddly differences between small insects

He had read Principles of Geology by Charles Lyell, which explained that the islands had only recently emerged from the sea as a result of volcanic activity. This led Darwin to wonder whether the beetles' ancestors had flown over from Spain and Africa. However, the mainland species were different from those on the islands, suggesting that the beetles had changed over time.

The key point is that Darwin was focusing on very fiddly differences between small insects. "It's only when you look at the details of individual species that you start to see the patterns," says Barclay.

"Darwin and Wallace were both beetle collectors," adds Barclay. "To me it is no coincidence that these two men, who were looking at a very large group with minute variations, made such fundamental breakthroughs. If you look at a large group like beetles in detail, you are able to see a world that has a lot more pixels than you might otherwise see."

Species-collecting can also help us preserve the natural world. Many species are enormously useful to us: not just by supplying food or wood, but by cleaning our water supply or pollinating our crops. If we understand the variations between species, we can figure out the ways in which they each benefit us, and preserve those benefits. It's hard to save what you don't know about.

Fortunately, Bornemissza knew his dung beetles

And sometimes, it can just be immediately useful. When the Hungarian entomologist George Bornemissza arrived in Australia in 1951, he noticed that cattle dung hung around for unusually long periods on Australian farms. All this poo meant there was much less land available for grazing. The question was, why was it there?

Bornemissza figured out that Australia's native dung beetles were adapted to deal with the small, hard dung of kangaroos and wombats. They couldn't cope with the large, splatty poo of cattle, which had only been introduced in the 1880s. Fortunately, Bornemissza knew his dung beetles. After a series of experiments he helped develop, around 50 species of foreign dung beetle were introduced over 20 years to clean up the cows' mess.

"It was an astonishing example of the massive economic effect of detailed examination of entomology," says Barclay. Bornemissza's dung beetles might not have been as pretty as Chatzimanolis's rove beetles, but they proved to be thoroughly important.

And if that doesn't persuade you to go take a close look at a seemingly dull lifeform, we don't know what will.