How? Those are not giant spider alien things. There dead humans that are alive
In Starship Troopers the bugs weren't smart, but they had insane numbers(spoilers otherwise, but still). In fact, the bugs did the exact same thing in the trailer--they were so numerous that as they were killed they formed hills large enough to climb over walls and overrun a fort.
It's gonna be amazing. I'm also looking forward to movies like After Earth and Oblivion this year, none of them are about zombies, but still worth mentioning!