The scientists who conducted the experiment described on the last page didn't attempt to collect a sample of every insect species on Earth, but they were able to get a better grasp on the amount of diversity that exists across two separate U.S. regions. And that bumper? It yielded samples from 711 and 1,516 members of the Insecta class in the two regions tested [source: Calicchia].
Globally, scientists have identified about 925,000 species of insects, says Hogg, the entomology professor. Estimates on the number of total insects species fall as high as 30 million and as low as 2 million. The estimate that many people agree upon is about 5 million, so biologists have yet to identify more than 80 percent of the estimated total number of species [source: Hogg]. You can see the complications and uncertainty involved in assigning a number for the total of individual insects out there.
So if you were an entomologist determined to make your mark in the field, a better bet might be to discover a new insect species or two. Where might you look (and be prone to swatting a lot away as you search)? The tropics are the world's most populous places in terms of insects, and tropical environments near the equator are also most conducive to plant and animal diversity [source: Hogg]. Ants are probably Earth's most abundant insect species, says Hogg. In fact, in the tropics, the total biomass (weight) of ants is greater than that of all of the mammals combined.
The United States has insects in great abundance, too. Hogg's research on aphids, an insect species that feeds on soybeans, took him to the Midwest. According to Hogg, in the peak of summer, one soybean plant can house up to 2,000 aphids. One acre can support up to 20,000 soybean plants, and in the upper Midwest, there are close to 40 million acres of soybeans. In other words, that's a lot of aphids -- 1.6 x 1015. But that's just aphids. You came here to learn how many insects there are on Earth, so we're not going to send you away disappointed.
The estimated number of individual insects currently hopping, crawling or flying around our planet at any given moment is about 10 quintillion, or the number "10" followed by 18 zeros, according to entomologist Dr. E.O. Wilson [source: Smithsonian Institute]. That means there are about 2 billion insects for every human being, and assuming that there are 5 million species of insects, that means that each species has about 50 trillion individuals [source: Hogg]. So the next time you feel outnumbered, just remember: Unless you're an insect, so is everyone else.