Muto to be a reptilian monster

From the fairly recent Asian trailer I noticed something that counters my previous thoughts. Muto most likely will be a reptilian lizard. If you look at how in the trailer it's gliding, not an insect flight patter but instead more of a bird. Bees, Butterflies, moths, and any other insect that flies must constantly flap it's wings to sustain flight at all. But birds and even reptilian airborn organisms would flap to gain height and then glide. Which is what I see in the Muto. 

What caused my thoughts about it's insectual side was the cocoon, the eggs alined across the missile and it's roar.

But the aggressiveness, wing form, and flight style make me think otherwise.

What do you think guys? Will the muto be an insect or a reptile