There's a story in the comics in which Mantis briefly turns into a baby. I'm not sure what it's called, the whole arc was time/space nonsense with Starhawk. Point being, while baby Mantis was cute, she did not look like a bug.
Baby Mantis should look like a bug. So I tried to make a growth chart for Mantis, starting with a bug.
From left to right: Baby (0-12 months), Toddler (2-3), Small Child (5-8ish), Tween (10-13), Teen to Adult years (14+)