This question was submitted by Kathleen of Virginia. Thanks, Kathleen!
Much like the tallest building, determining the biggest insect question is challenging in that it really all depends on how you define biggest. Do you want to know what the longest insect is, what the heaviest insect is or what the bulkiest insect is? Biggest bug, unfortunately, leaves room for speculation. Since I don’t know what you define as “biggest” I’ll give you the best answers I can find.
Weight - The overall mass of an insect is what your average entomologist would probably consider the real criteria for the size question. The record holder there is the Goliath Beetle, a member of the Scarab family. While this insect only grows to be about 4.5” long, their sheer weight makes them a top contender for the “Biggest” prize at 100 grams (more than a small bird). The picture to the left, from ExtremeScience.com, is of a Goliath Beetle clinging to the forearm of an ADULT MAN! Visit ExtremeScience to read more about these harmless and important creatures as well as a lot of other interesting topics!
Not as heavy (71grams), the still massive New Zealand Weta is also deserving of mention in the Mass category. For some great pictures of the Weta, visit http://nzphoto.tripod.com/animal/weta.htm
Bulk - Often mentioned as one of the “largest” insect, the Acteaeom (or Acteon/Actaeon) Beetle often receives an entomological nod of approval. This thing takes up a lot of space! 5.3 inches long by 2 inches wide and 1.5 inches thick, it isn’t as heavy as the Goliath nor as long as our next contender, but for overall space occupied, it’s certainly worthy of mention. Cute looking fella, isn’t he? You can see more great pictures of this notable giant at http://www.goliathus.com/en/en-megasoma-actaeon-actaeon.html including some great close-ups!
The South African Longhorn beetle is our next honorable mention at about 6.3 inches in length. It’s not as bulky as the Acteon but I imagine most of us would pay it a fair amount of respect if we woke up to it crawling on us. Thanks to ScienceBob for this great picture. A bug in the hand is worth… well I don’t know what it’s worth but my skin is crawling.
Wingspan - The largest wingspan recorded on a bug is a fossilized dragonfly with a wingspan of over three feet!
Our last candidate isn’t bulky nor is it massive, but I think you’d still call it big if you saw one!
Length - The Giant Walking Stick insect is our winner for length. It would probably lose a wrestling match with any of our previous contenders, but it’s the bug you’d want to call if you ever needed something from the top shelf. They can grow up to 20 inches in length!