Useless

The spider landed in front of them as if implying that they could challenge him directly. 

"Kh." Noel gritted his teeth. There were two big problems with that jump alone. First of all, that colossal body would be extremely heavy if the spider was able to create such a tremor from jumping alone. They could easily get squashed by that giant body if they were not careful.

The second problem would be the spider's mobility. It was said that ants were moving much faster than humans, but because humans had a far greater reach, they would never outrun humans. 

Right now, Noel and Anna are the ants. The fact that it could easily jump meant the spider could run as well. If it decided to chase after them, the spider could easily catch up to them.

In other words, they had nowhere to run.