First thing we have to consider here is the Emperor Sea Strider's weaponry. Its a giant bipedal animal that stands 620 feet tall (the documentary version is a whole lot shorter, but the image above is from the book, so I'll base this on the bigger book version).
However, this doesn't fully explain why the Emperor Sea Strider gets so big. You see, when scientists re-examined the book "Expedition" by Wayne Douglas Barlowe, they realized that, even on a planet with as little gravity as Darwin IV,
After all, it would have to be smaller...unless it was made out of stronger than normal biological material.
Just like Mothra and Godzilla are made out of.
However, this assumes that the Skewers didn't find a soft spot or
Hence, there is no objection to the idea that the Emperor Sea Strider has developed stronger than normal biological material, and thus has become far larger than what is normally biologically possible, just like
So, given this, could the Emperor Sea Strider take on Mothra?
Well, for starters, Mothra can fly around, and is pretty intelligent, while the Emperor Sea Strider is not the brightest or fastest monster around. Indeed, its mouths, which could potentially
However, the Emperor Sea Strider may have one potentially powerful weapon:
Sonar.
Sonar can damage animals. Indeed, submarines have been known to deafen whales with their sonar pings. Whales see through sonar, so to be deafened like this would mean certain death. Thus the Sea Strider, if threatened, may unleash a mighty sonar ping that could rattle
Then again...,maybe not.
You see, skewers did on one recorded occasion take down an Emperor Sea Strider, and though they are big, they are nowhere NEAR as big as a Sea Strider. If a Strider could use such sonar as a weapon, why didn't it do so then?
Either its because they were incapable of using sonar as a weapon, the Skewers had developed an immunity to sonar-based attacks
And since Mothra has no experience with such attacks, the Emperor Sea Strider could rattle it.
Still, Mothra is freaking tough, and like the
Thus, I must conclude...