With well over one million insect species on Earth, the title of "Biggest Living Insect" would be an extraordinary achievement for any bug. Before we can confer such an award to a single insect, however, we need to determine how we measure bigness.
What makes a bug big? Is it sheer bulk that defines a creature as large? Or something we measure with a ruler or tape measure, determined by centimeters? In truth, which insect wins the title depends on how you measure an insect, and who you ask.
Measure an insect from the front of the head to the tip of the abdomen, and you can determine its body length. That might be one way to choose the biggest living insect. If that's your criteria, your newest world champion was crowned in 2008, when entomologists discovered a new stick insect species in Borneo. Chan's megastick, Phobaeticus chain, measures a full 14 inches from head to abdomen, and a full 22 inches if you stretch the tape measure to include its extended legs. Stick insects dominate the competition in the longest insect category. Prior to the discovery of Chan's megastick, another walkingstick, Pharnacia serratipes, held the title.
For many insects, its wings spread far wider than the size of its body. Would wing span be a good measure of an insect's size? If so, you're looking for a champion among the Lepidoptera. Of all the living insects, butterflies and moths have the largest wing spans. The Queen Alexandra's birdwing, Ornithoptera alexandrae, first earned the title of the world's largest butterfly in 1906, and in over a century, no larger butterfly has been discovered. This rare species, which lives only in a small area of Papua New Guinea, can measure over 25 cm from wing tip to wing tip. While that's impressive, a moth would hold the biggest living insect title if wing span was the sole criteria. The white witch moth, Thysania agrippina, outstretches any other Lepidoptera with a wing span of up to 28 cm (or 11 inches).
If you're looking for a bulky bug to anoint as the biggest living insect, look to the Coleoptera. Among the beetles, you'll find several species with a body mass that is the stuff of science fiction movies. Giant scarabs are known for their impressive size, and among this group, four species remain deadlocked in the competition for biggest: Goliathus goliatus, Goliathus regius, Megasoma actaeon, and Megasoma elephas. A lone cerambycid, the aptly named Titanus giganteus, is equally massive. According to the Book of Insect Records, researched and compiled by the University of Florida, there is no credible way to break the tie between these five species for the title of bulkiest bug.
Finally, there's one last way to think of bigness when it comes to insects – weight. We could put insects on a scale, one by one, and determine which is biggest by grams alone. In that case, there's a clear winner. The giant weta, Deinacrida heteracantha, hails from New Zealand. An individual of this species weighed in at 71 grams, though it's important to note the female specimen was carrying a full load of eggs at the time she stepped on the scale.
So which of these insects should be called the biggest living insect? It all depends on how you define big.