Yeah, you're right that's a giant hermit crab. Thanks for the correction.

Stomach corporation is selling illegal drugs, so it's natural that they eat each other without regard. Anything goes in the underworld. Nothing's illegal. It'd be more interesting if Lango and or Glotta end up give Nyelv the Fredo treatment.

My mistake was visual, while the writers' are logical ones. My mistaking hermit crab for a spider is a much smaller mistake compared to the so many instances of faulty reasoning and other forms of sloppy writing in this story, haha.

Agents can't asssume human disguises because human disguises can only be used by Granutes via a Gavv, which they don't have. Of course, it could happen if and only if the writers pull a Yuuya, haha.

This is why I consider absolute shapeshifting ability a dangerous trope very often abused by lazy, hack writers. If one or several key characters posses this ability, then they can be anyone and manipulate other characters. The worst is if they can also change other characters' appearance. It's a blank cheque on which a lazy writer can pull any kind of cheap twists and change the course of the story. It's basically cheating.

On the other hand, it can also bite the writers' hands, as this story has already shown. Granutes are said (and shown) to be able to easily assume any human disguises, yet Lango/Stomach has only equipped their Granute part-timers with alternate disguise for 1 episode only in episode 8 for Iwashimizu/fake art dealer who only had 1 alternate disguise. If Granutes can change the appearance of their human disguise as easy as changing the wallpaper on my smartphone then the only thing that makes sense that Lango/Stomach should already do is supplying their part-timers with infinite number of disguises. That would've greatly reduced the risk of being detected by humans and Shouma/Hanto/Kenzou. Then again, this story is sooooo sloppily written, so I won't expect anything that follows logic, rationality, and common sense, haha.