Meganeuropsis is an extinct genus of griffinfly, order Meganisoptera, known from the Early Permian (299-272 million years ago) of North America,and is the largest insect of all earths time. Meganeuropsis permiana described in 1937 from Kansas, was the largest known insects that ever lived, with an estimated wing length of 330 millimeters (13 in), an estimated wingspan of up to 710 millimeters (28 in), and body length from head to tail of almost 43 centimeters (17 in).
http://www.eartharchives.org/articles/the-biggest-insect-ever-was-a-huge-dragonfly/
This animal was a huge part of the food chain, and many scientists that there was nothing bigger than this insect at the time that flew with 6 or more legs.
