They came from outer space, like most obnoxious pests. Their ship was in good working order, their maps were up to date, and they were on schedule. Why then did they stop? They were hungry! Long range sensors picked up a planet with at least a few of those food sources that they loved: geothermal vents. Yes, the food suckers loved nothing better than dining on the stinking, hot, sulfurous steam belched up from the interior of a cooling planet.
As soon as their ship cooled off enough to open the door, they slithered down a ramp and over to the nearest vent and started eating up. However, the vent was small, and only a few food suckers could get close enough to divert the planet's energy into their gaping mouths. No problem. The rest just moved in close, hooked up their food intake bypass ports to other creatures around them, and sucked in food from their neighbors. Slowly a network of interconnected food suckers grew, but only where there was water enough to drink, because the food suckers hadn't yet invented a pipe for sharing water. Oh too bad.
What the suckers didn't realize was that not only was the water full of the nutritious elements they needed to keep their slime trails healthy, but it was also chock full of a compound that caused these same slime trails to harden into extremely tough glue. They were stuck in place, trapped on a backwater planet with no hope of escape! Oh what will they do? Will someone come who can provide them with a means of escape, or at least some better placed food sources and watering holes so that their population can grow?