So, assuming you mean to imply that DMT "insects" are real creatures composed of dark matter, such a being would still be affected by Earth's gravity if it was nearby, even if it couldn't interact with our "normal" matter at all. This seems to imply that it would be pulled through the surface of the earth, towards the center.

So if any of you see intelligent insects walking around on your next DMT trip, ask them how they keep from being sucked into the planet.