[Doctor DNA]

They were bigger then cause there was much more oxygen in the air. The primitive breathing of insects limits the size .... so I heard. bzzzzzz

[Doctor DNA]

Thats why those movies with the giant spiders and ants are so hokey! Even giant monsters mammals and fishes .....

[JimSEA]

They are arguing about that now. Most go with the obvious and necessary higher oxygen levels but some bird fans are saying they hunted the biggest ones and smaller insects evolved. Might both have a point.