It's called a Nincada. The Dex says they like to keep to the shadows and rarely come above ground.

[And she didn't miss the significance of that, which admittedly bothers her a little — ah, but Naegi only just woke up in the garbage room, didn't he, so he hasn't heard her story during the long climb together.

Well, then, she'll just remain cryptic and amused. It's better than being cryptic and unsettled.]

They're different for every person, aren't they?