Early in the 1980s, Terry Erwin of the Smithsonians National Museum of Natural History (NMNH) gathered data on tropical forest insects by fogging trees with insecticide and collecting the specimens that fell from the canopy. According to Erwin: Peter Raven, Missouri Botanical Gardens director, asked me how many insect species were in one acre of tropical forest. I said I would get back to him. Using my data from trees fogged in Panama in 1974, I calculated about 46,000 insects per hectare. But then I had another idea. Erwins idea, to estimate the total number of insect species worldwide based on a chain of field-testable hypotheses, was the pistol shot that started the race to understand global biodiversity.
Erwin established a high-end estimate of 30 million insect species on Earth, based on 955 species of beetles collected by fogging 19 individuals of a single tree species in Panama. He used a guestimate that 13.5% of the beetles were monophagous, that is, they depend upon one tree species for survival and multiplied the estimated total number of herbivores by the estimated number of total tree species. He then added in the fungivores, predators and other insects to arrive at the 30 million total. Erwin concluded his one-page publication by stating: I would hope that someone will challenge th
Contact: Michele Urie, NMNH Office of Public Affairs
Smithsonian Tropical Research Institute