Giant insects have been featured in science fiction films for years, but how big can they actually get ?
Researchers aren't exactly sure what limits the growth of insects. One possibility is that their exoskeletons may not be strong enough to support anything over a certain size, another is that if insects were too large they would make for too convenient a meal and that a smaller size helps them to avoid predators.
The most likely theory however is that insect size is limited by the amount of oxygen in the atmosphere. Fossils dating back 300 million years show that insects in the distant past were significantly larger than their modern counterparts most likely because there was a lot more oxygen in the air at the time. The more oxygen - the larger the insect and vice versa. There simply isn't enough oxygen in the atmosphere in the present day to support insects beyond a certain size.
"Support for this theory comes from the fact that about 300 million years ago, many insects were much larger than they are today."
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Source: Live Science
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