We talked about the giant insects in the Pennsylvanian coal swamps last month. Insects continued, of course, into the Permian, but the changing environments mean that the record is considerably less extensive because of poor preservation of insects. Coal swamps were great places to fossilize bugs, while more arid river systems and even deserts were not.
One of the common ideas for the gigantic size of insects in the Pennsylvanian was the increased oxygen content at that time. There was a crash in oxygen levels toward the end of the Pennsylvanian and into the early Permian, perhaps related to the crash in the rainforest ecosystem – but gigantic insects are found in the Permian too, including one called Meganeuropsis, the largest insect known with a wingspan of 28 inches and a body length of 17 inches. So there is still research to do on the relationship between oxygen in the atmosphere and the evolution and size of insects.
The most common Permian insects are cockroaches and their relatives. The first true dragonflies probably evolved in the Permian from Pennsylvanian dragonfly-like ancestors. Until recently, the oldest known beetle was from the Permian, but in 2009 a fossil beetle was described in the Pennsylvanian Mazon Creek rocks. Beetles certainly did diversify during the Permian, and today there are at least 350,000 species of beetles.
—Richard I. Gibson
Modern Beetles predate Dinosaurs
The largest complete insect wing ever found