insects are so different from vertebrates (e.g. multi compartment bodies thanks to how they express the HOX gene) that the flying strategies are also quite different.
At the current level of O2 in the air I don't believe that flying insects can grow as large as even a hummingbird, much less an eagle.
The insect grows up to 7 cm in length whereas the bird can stay less than 6 cm at adulthood. No information about the insect weight though (for a proper comparison).
At the current level of O2 in the air I don't believe that flying insects can grow as large as even a hummingbird, much less an eagle.