The Biggest Insect Ever Existed Was A Giant 'Dragonfly'

In the case of the giant dragonflies, the presence of very large Meganeuridae with wing spans rivaling those of Meganeura during the Permian, when the atmospheric oxygen content was already much lower than in the Carboniferous, presented a problem for the oxygen-related explanations. However, despite the fact that Meganeurids had the largest known wing spans, their bodies were not very heavy, being less colossal than those of many living Coleoptera; therefore, they were not true giant insects, only giant in comparison with their living relatives. Other explanations for the large size of Meganeurids compared to living relatives are warranted. Bechly (2004) suggested that the lack of aerial vertebrate predators allowed pterygote insects to evolve to maximum sizes during the Carboniferous and Permian periods, perhaps accelerated by an evolutionary arms race for increase in body size between plant-feeding Palaeodictyoptera and Meganisoptera as their predators.