I found the answer to my own question >>5015116

It looks like butterworts secret digestive juices wherever the prey is located. The insect in the top left of this picture was in the center of the leaf, but after it released it's digestive juices, it caused it to glide down toward the edge of the leaf, leaving a trail behind it.
Also in this picture, trapped fungus gnats and their larvae(which I plucked from it's pot and fed to it because its what they deserve.